Considering Safety in the Transportation Planning Process
Chapter 2: Safety as Part of Long-Range Transportation Planning Process
Long-range transportation planning is a process by which states and MPOs determine their desired transportation system and then work toward achieving it. Transportation planners examine demographic characteristics and travel patterns for a given area to predict the future needs of the transportation system. Planners analyze alternatives for the area's transportation system. This is provided to the decision makers who evaluate the alternatives to determine the most expeditious use of local, state, and federal transportation funding to provide a system to meet those future needs.
The result of the long-range transportation planning process is a document, the adopted long-range transportation plan. Both the regional and statewide processes result in a long-range transportation plan. The document is a collaboration of the region's or state's transportation systems and is the defining vision for the transportation system and services. In metropolitan areas, the plan notes all of the transportation improvements scheduled for funding during the next 20 years.
Long-range planning is typically done over a 20-year or more period. Long-range planning provides input for short-range programming of specific projects, which usually covers a 3-to-5-year period.
The Transportation Equity Act for the 21st Century (TEA-21) specified that both the statewide and metropolitan transportation planning processes "shall provide for the consideration of projects and strategies that will increase the safety and security of the transportation system for motorized and non-motorized users."
State and metropolitan transportation planners can facilitate the incorporation of safety into the transportation planning process by providing a forum for safety and encouraging the consideration of safety in long-range transportation strategies. Safety can formally be incorporated into the long-range transportation planning process by developing long-range safety goals, objectives, and performance measures and evaluating progress toward those goals, whether the progress is regionwide or through individual projects. Long-range approaches, such as predictive modeling, can help guide transportation decisions to accomplish the safety goals and objectives of the long-range plan.
Transportation planners will most likely experience some challenges when incorporating safety into the long-range transportation planning process. However, some state and metropolitan planners are finding methods through which safety can be incorporated. This chapter provides transportation planners with guidance on how safety has been incorporated into the long-range transportation planning process. Potential challenges are also identified and discussed.
Providing a Forum for Safety
State and metropolitan transportation planners can facilitate the incorporation of safety into the long-range transportation planning process by providing a forum, such as a safety conference or a formal meeting, for safety partner involvement. Providing this forum could help to enhance communication and understanding among transportation planners and safety practitioners about the respective planning processes that exist and the opportunities for safety to be included in long-range planning. For example, the transportation planner could organize a conference on pedestrian safety in the region. In addition to all involved transportation planning agencies and safety practitioners, forums could include representatives from various aspects of the transportation system including:
- Local planning organizations
- Public and private safety-related organizations and associations
- Neighborhood and community groups (including groups of senior citizens, persons with disabilities, mothers of small children, etc.)
- Enforcement personnel
- Land use policy and development groups
- School district representatives
- Motor vehicle safety and operations professionals
- Elected officials
- Bicycle and pedestrian advocacy organizations
- Members of the media
Long-range transportation planning must be multi-modal in nature. It should consider the safety of all users in the transportation system including pedestrians, bicyclists, motorists, transit riders, and heavy vehicles. Providing a forum for safety can facilitate the consideration of the needs of all system users in the long-range transportation planning process. However, long-range transportation strategies employed to increase the safety of one user may decrease the safety of another. The balance between the needs of these users and their effects on one another must be considered. Members of the forum could identify these issues and develop strategies to provide this balance.
A forum for safety can provide a good starting point for incorporating safety into transportation planning activities. The collaboration of all interested parties can strengthen the incorporation of safety into the long-range transportation planning process and can help overcome some of the current challenges.
Goals and Objectives in Long-Range Transportation Planning
The development of long-range transportation planning goals is essential to the incorporation of safety into the long-range transportation planning process. Including safety as a goal in the long-range plan helps establish the importance of safety among various interests in the competition for limited financial resources. It identifies safety as a priority. Most MPOs and DOTs have safety goals, although many do not have performance measures. However, there has been an increasing trend in the past several years to incorporate performance measures in state and metropolitan plans.
Several issues must be considered when developing safety goals. Safety goals represent broad targets. Goals are typically somewhat vague and general although they should be within the sphere of the transportation system and obtainable. Developed through citizen input, the goals represent the general themes and overall direction envisioned for the transportation system, which in turn is carried out through tangible objectives. Objectives are more precise and measurable; they provide specificity and focus for the goals. Together, goals and objectives provide a policy framework to develop and implement the long-range plan. For example, a safety goal may be to improve pedestrian safety. This goal would be translated into objectives such as "reduce pedestrian fatalities at intersections." Safety objectives should be well defined, obtainable, and measurable.
Often, there is a delicate balance between goals. Achieving one goal can often mean that another goal will not be achieved. For example, the goals of increased mobility and increased safety can often conflict. A project that increases the mobility of an area may decrease the safety. Transportation planning agencies should attempt to find a balance between the goals.
Planning agencies should consider the following when developing safety goals and objectives:
- Reasonable and Obtainable: Safety goals should be carefully chosen so that they can be reasonably accomplished through investment in the transportation system. Those goals should be translated into obtainable safety objectives.
- Multi-Modal: Safety is important to users of all transportation modes. Safety goals and objectives should be multi-modal and include highway, transit, freight, pedestrian, and bicycle considerations.
- Public Involvement: As with all goals and objectives in the planning process, the formation of safety goals and objectives can be greatly facilitated with public involvement and support. Public support or "buy-in" of the safety goals and objectives demonstrates support of the community's own safety.
- Assessment of Safety: Because resources are usually limited and the need for them is competitive, current transportation system safety needs to be assessed and prioritized.
- Timeframe: It is also beneficial in developing objectives to include target completion dates.
Once safety goals and objectives are established, they can be used to formulate transportation strategies including policies and initiatives. They can also be used in selecting projects and in evaluating alternatives at the project-planning level. This is discussed further in Chapter 3.
Performance Measures and Monitoring Progress
Performance measures monitor progress toward the established safety goals and objectives. Performance measures, or measures of effectiveness (MOEs), are used in the planning process to report on how well goals and objectives are being achieved. Performance measures are used to answer the question: "Are we achieving what we set out to accomplish?"
The selection of appropriate performance measures is essential. Performance measures should be quantifiable so that progress toward goals and objectives can be practically and objectively measured or monitored. A performance measure must provide timely and accurate assessment of progress.
For a long-range plan, progress toward each of the objectives should be evaluated regularly (for example, annually) using the performance measures. The progress evaluation can be used to revise or refine the goals or objectives for inclusion in subsequent plans. The evaluation should alert the planning agency if the transportation investment allocation needs to be adjusted to achieve the goals and objectives. In addition, the performance measures should be evaluated to determine if they are accurately monitoring progress toward achieving the goals and objectives.
| Monitoring Performance in the Delaware Valley Region |
|---|
The Delaware Valley Regional Planning Commission (DVRPC) published a report on the region's progress toward meeting the goals and policies set forth in the 2020 long-range plan (1). The report was part of a 2-year effort to update the long-range regional plan and produce Horizons, The Year 2025 Plan for the Delaware Valley. The 2020 plan had developed goals, policies, and recommended actions in specific areas for improvements in future development and transportation. Mobility was one of eight specific areas. The mobility goal was to "improve access to and efficiency of the region's transportation network, and ensure the safety and security of the system's user." [Emphasis added.] The safety of the transportation system, road conditions, and reliability of public transit were identified as indicators of the progress toward the mobility goal. Improving these three indicators was the unstated objective of the plan. The combined numbers of fatal crashes, injury crashes, and property-damage-only crashes were used to measure the performance toward the long-range goal of improving mobility. DVRPC used crash data from 1988 through 1995 from New Jersey and Pennsylvania to determine that, region-wide, total crashes decreased by 17.7 percent. Data was presented individually for each of the nine counties in the region. Between 1995 and 1998, crashes in the Pennsylvania side of the region increased by 3.3 percent. (Data from New Jersey was not available beyond 1995 to be included in the report.) |
Examples of Safety Goals, Objectives, and Performance Measures
Exhibit 2-1 presents examples of safety goals with accompanying objectives and performance measures for highway, pedestrian, heavy vehicle, and transit safety. Each goal provides potential objectives and performance measures that could be incorporated into long-range planning to increase safety.
Exhibit 2-1
Examples of Safety Goals, Objectives, and Performance Measures
| Goals | Objectives | Performance Measures |
|---|---|---|
| Increase highway safety | Reduce highway fatalities 10 percent by 2020 | Number of fatal highway crashes |
| Rate of fatal highway crashes | ||
| Total number of people fatally injured in highway crashes | ||
| Reduce highway crashes 10 percent by 2020 | Number of motor vehicle highway crashes | |
| Rate of motor vehicle highway crashes | ||
| Increase pedestrian safety | Reduce pedestrian crashes | Number of pedestrian crashes |
| Number of pedestrian fatalities | ||
| Number of pedestrian crashes resulting in an incapacitating injury or a fatality | ||
| Increase heavy vehicle transportation safety | Improve heavy vehicle safety on the highway | Number of highway crashes involving a heavy vehicle |
| Percentage of highway crashes involving a heavy vehicle | ||
| Number of fatal and incapacitating injury crashes involving a heavy vehicle | ||
| Percentage of fatal and incapacitating injury crashes involving a heavy vehicle | ||
| Rate of heavy vehicle crashes on the highway (using heavy vehicle miles travels as exposure) | ||
| Improve transit system safety | Reduce incidence of transit vehicle crashes | Number of transit vehicle crashes |
| Rate of transit vehicle crashes (with transit miles traveled used as exposure) | ||
| Increase safety of transit riders before and after boarding transit vehicle | Number of pedestrian crashes within 250 feet of transit stops | |
| Number of pedestrian crashes involving transit vehicles | ||
| Number of midblock transit stops | ||
| Number of midblock transit stops with positive barrier systems to discourage pedestrians from crossing at non-designated pedestrian crossing points |
Many state DOT planning agencies address long-range transportation safety in the goals or mission statements of their long-range plans. Some of these long-range plans are briefly described in the following paragraphs.
Alabama Department of Transportation
The Alabama Statewide Transportation Plan has four long-range goals, the first of which addresses safety (2). This goal is addressed through five objectives. Measures of effectiveness are not presented in the plan.
Goal 1: Provide safe and efficient transportation for people and goods
Objectives
- Monitor and reduce, where possible, the rate of motor vehicle, bicycle and pedestrian accidents, injuries and fatalities on the state's roadways.
- Improve the safety of commercial vehicles, rail facilities, airports, and public transit vehicles and facilities.
- Improve the safety of intermodal connections and crossings, such as highway and railroad bridges over waterways, railway/highway crossings, and intermodal terminals.
- Improve transportation facilities for emergency management, including natural disasters, hazardous materials and other public emergencies.
- Address safety issues in the design of facilities, establishment of programs, construction, operations, maintenance, and all phases of development and use of transportation.
Pennsylvania Department of Transportation
In 1998, the Pennsylvania Department of Transportation (PENNDOT) conducted a statewide customer survey to understand the degree of importance and the levels of concern about a variety of safety and traffic topics. Safety was identified by 42 percent of the respondents as more important to them than smooth pavement, reduced congestion, and increased capacity. The results of the survey established a framework for the statewide long-range transportation plan, PennPlan Moves! The plan presents 10 goals that were identified by soliciting input from the public and professional communities. The first of these 10 goals is to promote the safety of the transportation system. Thirty objectives were drafted to address these 10 goals. Many of those objectives addressed multiple goals. According to the plan, 18 of the objectives correspond to the safety goal. A performance measure and target level of that measure is presented for each objective. One objective is to reduce the number of fatalities and severity of crashes on the state's highways. For that objective, the performance measure is overall injuries and overall fatalities. Thirteen types of fatalities are specifically identified including fatalities of 16- and 17-year-old drivers/passengers and 65-and-older drivers/passengers; fatalities involving drivers with revoked/suspended licenses, heavy trucks, and buses; fatalities involving alcohol; fatalities involving failure to use seat belts; fatalities involving pedestrians and bicyclists, and motorcyclists; and fatalities in collisions with fixed objects, in head-on collisions, at stop-controlled and signalized intersections, and on curves. The target, or MOE, is to reduce fatalities across all categories 10 percent by 2002, 15 percent by 2004, 20 percent by 2008, and 40 percent by 2020 (3).
Pennsylvania DOT's Statewide Progress
In June 2001, PENNDOT published the first long-range plan progress report, PennPlan 2000 Achievement Report (4). The report outlines the first-year progress toward the objectives of PennPlan Moves! The report was distributed to all planning partners so they could see how projects and programs across the state were helping to fulfill the long-range goals of the state, including the long-range safety goals.
The report describes the progress made toward each of the 30 statewide objectives outlined in the long-range plan. Progress is reported in terms of the performance measures defined for each objective. Many of the targets for the first year were met. The fourth objective was to reduce the number of fatalities and severity of crashes on the state's highways. Originally, the target was to reduce fatalities across all of the identified categories 10 percent by 2002, 15 percent by 2004, 20 percent by 2008, and 40 percent by 2020. However, after the publication of the long-range plan, these targets were modified to reflect goals in the Commonwealth's new strategic plan for transportation, Moving Pennsylvania Forward: A Transportation Strategy. The modified targets were to reduce fatalities across all categories of 5 percent by 2002 and 10 percent by 2005. The achievement report conveys that the state is progressing toward the new targets. Statewide, fatalities have been reduced by 2 percent since 1999.
The long-range plan also identified 28 corridors of statewide significance, each with its own objectives. The achievement report describes the progress toward the objectives of each corridor. In 15 of the corridors, at least one objective involves a safety improvement for a portion of the corridor. According to the achievement report, in all but one of the corridors, progress was made in the last year toward improving safety. In some corridors, safety improvements were being designed or constructed. In other corridors, safety improvements had been completed.
The achievement report illustrates that, overall, Pennsylvania is on its way toward achieving PennPlan's goals. Achievement reports will be published annually to continue tracking this progress.
Florida
Florida Transportation Mission:
Florida will provide and manage a safe transportation system that ensures the mobility of people and goods, while enhancing economic competitiveness and the quality of our environment and communities. [Emphasis added.]
The Florida long-range transportation plan has four goals: safety, system management, economic competitiveness, and quality of life (5). The safety goal will be accomplished through the following long-range objectives:
- Reduce the rates of motor vehicle, bicycle and pedestrian fatalities.
- Improve the safety of highway/railroad crossings and other locations where modes intersect.
- Improve the safety of commercial vehicle operations.
- Improve the safety of seaport, rail, and public airport facilities.
- Improve the safety of services, vehicles, and facilities for transit and for the transportation disadvantaged.
- Minimize response times of each entity responsible for responding to crashes and other incidents.
- Implement hurricane response and evacuation plans in cooperation with emergency management agencies.
The Florida transportation plan addresses safety in the goals and objectives, but like many state long-range plans, has no corresponding measures of effectiveness for each of the objectives.
Applying Goals, Objectives, and Performance Measures
Long-Range Corridor Planning
Most of the discussion about the identification of goals, objectives, and performance measures has been in the context of long-range plans; however, the same procedures can also be applied to evaluating transportation project alternatives. Transportation planners could use the safety goals and objectives as a measure to evaluate future alternatives for both short-range and long-range project planning. A systematic process of alternative evaluation, which could be used by transportation planners, follows:
- Define goals, objectives, and performance measures.
- Identify problems and needs.
- Generate alternatives.
- Quantify performance measures.
- Conduct tradeoff analysis of costs (political, social, and economic).
- Identify best alternatives.
Although the actual process of evaluating alternatives takes place in steps 4 and 5, steps 1, 2, and 3 provide the means by which to evaluate. The evaluation process should be able to describe how well each alternative performs as measured by the goals and objectives and should be sufficiently well-structured to identify commonalities, differences, and tradeoffs that exist among the alternatives with respect to the various goals and objectives. Well-constructed safety objectives and measures of effectiveness should allow the decision-maker to compare alternatives.
This alternative evaluation process can be used in long-range corridor planning projects. Exhibit 2-2 illustrates the levels of transportation planning. MPOs and DOTs planning offices are more involved with the broader levels of planning. As the levels become more site specific, MPO and DOT planning office involvement decreases while the implementing agency involvement increases. The corridor level of planning, a broad level below regional planning, may encompass multiple routes and various modes of transportation between two major destinations or urban areas. Corridor-level planning may be composed of multiple smaller projects within the corridor on major arterials, minor arterials, transit routes, and multi-use trails.
Exhibit 2-2
Levels of Transportation Planning
Corridor level planning can be both short-range planning and long-range planning depending on the time horizon of the project. Short-range corridor planning is addressed in Chapter 3. An excellent example of using safety goals and objectives to evaluate transportation system alternatives in corridor project planning is in the Maryland I-270/U.S. 15 project.
Planning for the I-270 Multi-Modal Corridor in 2025
The I-270/U.S. 15 multi-modal corridor provides a link between the Washington, D.C., metropolitan area and central and western Maryland. It carries both local and long-distance trips. Because of its current condition and projected growth, the multi-modal corridor is being studied to investigate highway and transit options that will relieve congestion and improve safety conditions along the corridor. The project horizon for the long-range study is 2025.
Because the corridor is multi-modal, no single transportation strategy alone will solve the its transportation needs. Therefore, several transportation strategies are being considered in the alternatives analysis including a "no-build" alternative. The proposed alternatives and strategies will all have different effects on the transportation, environmental, and economic systems throughout the corridor and in the region. For prudent evaluation, the project team needed to develop a system for comparing the alternatives being considered. Using input from focus groups, the project team translated the purpose of the project into goals and objectives. Five goals were identified, and multiple objectives were discussed to address each of the goals. For each objective, the project team identified a MOE for the various aspects of each alternative. The process of defining MOEs is explained in the adjacent flowchart.
For the second goal, enhance mobility, 12 objectives were suggested. After discussion within the project team, six objectives were recommended. The fourth objective addressed the stated goal of improving the safety of the transportation system.
The safety performance of future highway, transit ways, and corridors is difficult to predict. However, some safety generalities can be applied. Higher functional class roadways (for example, controlled access freeways) have lower crash rates by VMT than lower functional class roadways (for example, undivided highways). Alternatives that reduced VMT on lower functional class roadways accomplish this objective better. Additionally, general safety performance of various transit modes (for example, light rail versus bus) can be compared using local safety data.
For the third goal, improve goods movement, the safety of truck travel was a concern. The project team decided that the safety of truck travel must be one of the objectives that the project addresses.
The project team considered ways to differentiate the safety of truck travel from the safety of general vehicle travel within the types of build alternatives that were being analyzed. The team discussed ways to improve the safety of truck travel such as separating trucks from general-use lanes, moving truck travel into non-peak periods, and/or moving trucks to higher order facilities. Finally, the team decided on simply comparing the percentage of trucks on the highway during the peak periods for each of the alternatives.
Using Safety Goals in Municipal Planning: West Pikeland, Pennsylvania
The County Planning Commission in Chester County, Pennsylvania, assists county municipalities in developing comprehensive long-range plans. Safety is one of the goals of the long-range plan that the planning commission helped the municipality of West Pikeland to develop (6). The township is concerned with balancing its scenic character and aesthetic value with its safety and mobility needs. According to the plan, safety and traffic congestion are two key factors that determine road network effectiveness. The following goal and objective were developed:
- Safety Goal: Provide for a safe and effective circulation system that minimally impacts the township's rural character, open space, and scenic roadways.
- Accompanying Objectives:
- Facilitate road safety improvements that comply with the township's functional classification system.
- Identify and improve circulation system deficiencies on an ongoing basis and coordinate road improvements with new development.
- Develop an access management program to reduce roadway conflicts and provide safe and efficient access to the road network.
- Identify and improve non-vehicular circulation networks.
To develop the safety goal and accompanying objectives, the County Planning Commission assisted the municipality in reviewing and analyzing traffic volumes, intersection levels of service, anticipated traffic growth, and 5 years of crash data. The crashes were roughly summarized by junction location, injury severity, and some causes. The analysis identified roadway features within the municipality, such as steep grades and sharp curves, that can negatively affect transportation safety. The features of the plan are summarized in the following paragraphs.
The plan identifies a list of road segments and conditions on those sections that can adversely affect transportation safety. The plan also suggests a list of projects for the PENNDOT 12-year program update. Leading the list of projects are two safety improvements at intersections within the township. Strategies and techniques are recommended based on the safety goal to address the identified transportation planning implications. The plan recommends giving the utmost importance to safety improvements throughout the township.
Three specific areas in the township are identified including two intersections and one route. The first intersection is already included in the 12-year program to receive channelization and traffic signal updates. The second intersection also includes a bridge update on an approach to the signal. After the bridge is updated, the plan suggests improving signage, adding left turn lanes, implementing access management strategies, and considerations for pedestrians. The suggested safety improvement to the identified routes is the addition of left turn lanes at all major intersections along the route.
Long-Range Planning Approaches
Including transportation safety as one of the goals of the transportation system is the first step in incorporating safety into the transportation planning process. However, for this goal to be realized, transportation policies and strategies must also consider safety. Many of the efforts to increase the safety of the transportation system will be carried out through short-range planning activities. However, long-range transportation planning approaches also hold some promise for improving the safety of the transportation system.
Risk and Exposure
The risk that a crash will occur is based on many variables. Crash risk varies widely by facility, mode traveled within a facility, and temporally. Many of the approaches to improving the safety of the transportation system focus on improving existing facilities where demand exists. However, transportation crash occurrences are a function of exposure; that is, generally the more miles traveled within a system, the more crashes are expected to occur. This is true for motor vehicle, pedestrian, bicycle, transit, and heavy vehicle crashes. Transportation planners can also influence the safety of the transportation system through long-range transportation strategies that affect this exposure. Transportation planners can improve the safety of the transportation system through reducing exposure, modifying exposure, and reducing exposure to conflicts. These three approaches are explained in the following paragraphs.
Reducing Exposure
Exposure for most forms of transportation can be expressed as vehicle miles traveled. As mentioned in the preceding section, transportation crashes are a function of exposure. One of the areas in which transportation planners, especially metropolitan transportation planners, can affect the safety of the transportation system is through reducing the miles traveled within the system (that is, reducing exposure). Transportation planners are responsible for coordinating long-range land-use decisions. The total VMT in a state or metropolitan area is influenced by transportation planning especially in relation to land use and transit options. Long-range transportation strategies that decrease the total VMT in an area will likely produce a corresponding decrease in the frequency of transportation crashes.
In the interest of pedestrians and bicyclists, this may involve long-range land-use decisions that allow for densely spaced development. The resulting environment would shorten the distance of pedestrian and bicycle trips and therefore reduce the users' overall exposure. For motor vehicles, this may involve planning highways that are the most direct link between activity generators. Direct trips would reduce the overall highway miles traveled and therefore reduce exposure.
Modifying Exposure
The state and metropolitan transportation planning process has the ability to direct the transportation system to help divert traffic volumes from less safe modes or functional classes to safer modes or functional classes; that is, they have the ability to manipulate the exposure. This is especially true in long-range transportation planning. As the long-range strategy is being formulated in the long-range plan, the transportation process can help to guide the future of the system to help reduce the exposure of unsafe modes or divert the traffic (exposure) to safer modes. However, changes in trip patterns will have system level impacts on the function of the transportation system. Those impacts could cause negative safety impacts elsewhere in the network. Those impacts would need to be evaluated and the trade offs would have to be analyzed. Additionally, methods to modify exposure (such as adding a lane on the freeway) can be more cost intensive than other solutions.
Highway Functional Class
As explained in the preceding section, traffic crashes are a function of exposure. The general risk for traffic crashes varies by highway functional class. Long-range transportation strategy can divert traffic volumes from the higher risk functional classes to the lower risk functional classes to increase transportation safety.
Exhibit 2-3 presents motor vehicle fatality rates by highway functional system calculated by the Bureau of Transportation Statistics. The rates, which are from 1998 fatality data from the 50 states and the District of Columbia, are represented as fatalities per 100 million vehicle miles. The fatality rate on rural highways is much greater than on urban highways. For rural highways, as the functional class of the roadways decrease, the fatality rate increases. This is generally true of urban highways, except for the "Other Arterial" functional class.
Exhibit 2-3
Motor Vehicle Fatality Rates by Highway Functional System for 1998
| Highway Functional System | Fatality Rate (per 100 million vehicle miles) |
|---|---|
| Rural | 2.39 |
| Interstate | 1.23 |
| Other Arterial | 2.38 |
| Collector | 2.94 |
| Local | 3.70 |
| Urban | 1.01 |
| Interstate | 0.61 |
| Other Arterial | 1.15 |
| Collector | 0.79 |
| Local | 1.28 |
Nationwide, highway crash rates by functional highway system are only available for fatal crashes. However, similar fatality rates, injury rates, and total crash rates could be calculated for a jurisdiction and then used in long-range transportation planning. Transportation planners could use these rates to evaluate the safety of various transportation strategies. Planners could promote and support transportation strategies that decrease VMT on the lower functional classes such as local roads and, instead, divert those vehicle miles that are traveled on the higher functional class highways such as arterials. For example, a proposed transportation alternative that reduced the amount of vehicle miles driven on rural collectors and instead diverted those miles driven to rural interstate or rural arterials would be expected to increase the overall highway safety of the jurisdiction. This may be accomplished through improving access to rural interstates or expanding the rural arterial system.
Transit Alternatives
Transportation planners must prepare for future transit needs of transportation systems during the long-range transportation planning process. This may involve expanding the service of an existing transit system or introducing new transit service to an area. Various modes of transit are available including bus service, light rail, heavy rail, commuter rail, demand-responsive transit, and van pools. Each of the transit modes has different operating characteristics. One of those operating characteristics is the relative safety performance of each. When considering the future transit needs of the transportation system, the transportation planner must assess each transit mode available and determine which will best meet the needs of the area. Planners can incorporate safety into the long-range transportation planning process by considering the relative safety performance of each of the proposed transit modes as one of the aspects that is analyzed. If the proposed transit modes are already in operation in the region or in the state, planners could use the past safety performance of that mode's operation. Planners could also determine which transit modes operate the safest under different conditions. For example, they may find that bus service performs better in suburban areas than in urban areas. For future transit needs, planners may consider substituting urban bus service with a safer transit mode.
Exhibit 2-4 displays the transit crash rates based on total incidents occurring in 1999 on direct-operated urban transit systems. The number of fatalities, injured persons, and total incidents is represented by the number of vehicle miles for each transit mode. The rates were calculated by Federal Transit Administration (FTA).
Exhibit 2-4
Transit Fatality, Injury, and Accident Rates by Transit Mode for 1999
Transit Crash Rates for 1999
| Transit Mode | Fatalities per 100 Million Vehicle Miles | Injured Persons per 100 Million Vehicle Miles | Accidents per 100 Million Vehicle Miles |
|---|---|---|---|
| Motor Bus | 5.0 | 1,106 | 1,166 |
| Light Rail | 27.1 | 889 | 624 |
| Heavy Rail | 3.6 | 50 | 69 |
| Commuter Rail | 24.9 | 22 | 86 |
| Demand Responsive | 0.6 | 379 | 516 |
| Van Pool | 0 | 75 | 263 |
Because the rates are based on vehicle miles, the transportation planner must consider the relative occupancy of each mode in the analysis of safety. For example, van pools have a relatively low accident rate compared to light rail. However, light rail generally moves more passengers per vehicle mile than van pools because the vehicles have a higher passenger capacity. Although not presented here, national transit crash rates per passenger mile are available from FTA as reported in the National Transit Database. However, similar to highway rates, a state or metropolitan planning agency could calculate its own passenger-mile-based transit-crash rates by using the vehicle miles, total crashes, and average occupancy of each transit mode. Planners could use the resulting rates to evaluate the relative safety of the existing system and to predict the future performance of the transit system. For example, a transportation planner may use the rates to decide between extending a light-rail transit line to more stations or to increase motor-bus routes in those areas. The relative safety performance of each transit mode would be considered in the alternative evaluation. However, the relative safety performance would only be one of the considerations. There are other safety and passenger security issues, such as access, that would be considered in long-range planning transit alternative evaluation.
Pedestrians and Bicyclists
Transportation planners should consider the needs of all users in the long-range transportation planning process. Many state and metropolitan transportation planning agencies are developing long-range plans to protect pedestrians and bicyclist, who are especially vulnerable users. Planners can increase safety by using transportation strategies and investments to modify pedestrians' and bicyclists' exposure. Similar to highway users, the safety of these users can be increased by shifting trips traveled on less safe facilities to safer facilities.
To accomplish this, transportation planners must first identify which types of facilities are unsafe and which are safer. For example, planners may want to compare bicycle lanes, shared facilities, and paved shoulders. Planners equipped with this data could then plan and encourage the use of facilities that reduce pedestrian and bicycle crashes. The rate of pedestrian and bicyclist crashes by functional class or facility type is not readily available nationwide. Calculating pedestrian crash rates in relation to pedestrian exposure is difficult because adequate pedestrian activity data is generally lacking. This is also true of bicycle crash rates and exposure. However, pedestrian and bicyclist crash data may be more applicable if the numbers were developed individually for a state or an MPO region. State or metropolitan transportation planners could develop their own estimates of pedestrian or bicycle crash risk by facility type or functional class from the crash data within the jurisdiction. Transportation planners could coordinate with community members who are frequent pedestrians or bicyclists to identify where these trips are occurring. This could be facilitated through a safety forum.
When the safety of various pedestrian and bicycle facilities has been determined, transportation planners can use long-range transportation strategy to increase the safety of these users. This may be accomplished by replacing unsafe facilities with safer ones. Transportation planners may also identify access limitations to safer pedestrians and bicycle facilities and direct long-range transportation investment to providing access to safe facilities, thus shifting these users to the safer ones.
In the absence of data on pedestrian and bicycle crash risks by facility type, transportation planners could also use the operating speeds of facilities to quantify the general crash risk. Transportation research has identified the strongly associated relationship to higher vehicle speeds and the greater likelihood of pedestrian crashes and more serious resulting pedestrian injury (7). Long-range transportation strategies that divert pedestrian and bicyclists from high-speed roadways to lower speed roadways or lower vehicular speeds could be promoted to increase the safety of the transportation system.
Reducing Exposure to Conflicts
Transportation planners can use long-range transportation strategy and investment to increase the safety of the transportation system by reducing system users' exposure to conflicts with other system users. One of the foremost methods of reducing conflicts is through access management.
Highways and Access Management
For motor vehicle transportation, one of the most widely accepted method of reducing motor vehicle traffic exposure to conflicts is through access management. FHWA defines access management as "the process that provides access to land development while simultaneously preserving the flow of traffic on the surrounding system in terms of safety, capacity, and speed." Access management is the prudent control and planning of the location, design, and operation of driveways and street connections (that is, access) to a roadway. Access management has many goals. One of its foremost goals is to improve safety networkwide by decreasing crash rates. Transportation planners can incorporate safety into the long-range transportation planning process by promoting access management as a long-range transportation strategy.
The goals of access management are achieved through controlling and regulating direct access to roadways based on their functional class. In this way, roadways can operate better at their originally intended speed and capacity with the benefit of smoother vehicle flow, reduced delay, and reduced crashes. Every access point onto a roadway is a potential conflict point for vehicular movements. As the access points become more complex, the potential for crashes increase.
For the roadway system to operate effectively at its intended functional class, transportation planners must coordinate the system with the land use surrounding it. However, the relationship between the road's functional class and the land use is often dynamic. As a transportation system grows, it may stimulate growth and changes in land use. For example, transportation planners may decide to widen and repave a highway that bypasses a town in order to move traffic around the town more effectively. However, open space and traffic generated by the improved highway may attract shopping complexes and other developments to the outskirts of town also. The developments' needs for multiple driveways into their parking lots would produce access control issues. The increased access onto the improved highway would eventually increase the number of crashes and reduce the capacity of the roadway. Planners would need to integrate corridor, land use, and access management into the area's long-range plans to avoid this cycle.
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The Minnesota DOT developed a variety of publications for planners on the consideration and use of access management strategies. Although the publications were developed for planners in the state of Minnesota, the principles are applicable for all planners interested in using access management to increase the safety of the transportation system. The publications are available on the Minnesota DOT's web site. |
The Minnesota DOT's Office of Access Management is responsible for the state's access management. The goal of the program is to use access management to reduce congestion and crashes on the existing road system. The office develops recommendations for land use planning and for engineering and legal practices that affect the operational efficiency and safety of the roadways by functional class. To support its study, the office also analyzed the safety effects of access management.Heavy Vehicles
Crashes between heavy vehicles and lighter passenger cars are more likely to result in severe injuries or fatalities. One method of increasing transportation safety is by reducing conflicts and thereby severe crashes between passenger vehicles and heavy vehicles. Heavy vehicles are often restricted to specific routes (such as truck routes) that are more capable of handling their operating characteristics (turning radii, weight, deceleration ability). On some controlled access facilities, heavy vehicles are restricted from traveling in certain lanes. For example, on portions of Interstate 40 through North Carolina, heavy vehicles are restricted from traveling in the innermost lanes.
Some consideration has been given to providing either exclusive lanes for trucks and passenger vehicles on interstate highways or completely exclusive facilities. FHWA developed the Exclusive Vehicle Facilities (EVFS) computer program to determine the economic feasibility of separating light vehicles from heavy vehicles by designating existing lanes or constructing new exclusive lanes on sections of controlled-access highways. EVFS calculates the benefits and costs associated with separating light and heavy vehicles. Accident cost savings because of less severe accidents is one of the benefits considered. The program is for site-specific analyses only and not for regional, statewide, or national network analyses (8). The State of Virginia used EVFS to determine the economic feasibility of providing exclusive lanes for trucks and passenger vehicles on a segment of Interstate 81. The analysis revealed that many of the exclusive lane strategies would produce a positive benefit (9).
The Southern California Association of Governments (SCAG) approved the provision of a four-lane dedicated truck facility on a 37-mile stretch of State Route 60. SCAG is the MPO for the Los Angeles metropolitan area (10). The Association conducted a study on the feasibility of having dedicated truck facilities along State Route 60 partially because of concerns for safety, but predominantly because of significant truck volumes that were expected to increase by more than 60 percent by the year 2025. The facility has been approved for consideration in the long-range plan; however, financing is still needed for the estimated $4.3 billion project. The MPO is coordinating this project with the California DOT, the 3 area county transportation commissions, and the 30 municipalities that will be affected by this facility. Preliminary engineering studies and environmental impact statements are expected to be conducted in the next 2 to 3 years. If the project is funded and approved, construction is targeted to begin in 2010 (11).
Predicting the Safety Performance of the Transportation System
Transportation planners have fairly reliable tools and methods for evaluating alternatives to predict mobility-related performance measures such as levels of highway and transit use, delay, and overall system performance. However, for many safety MOEs, transportation planners may not have the necessary tools. When evaluating the future safety of an existing or planned project as an MOE, transportation planners must predict the project's future safety performance. The lack of a reliable method for estimating the safety performance of an existing or planned transportation facility has been identified as one of the most critical gaps in the management of highway safety. Potential methods to predict the long-range safety performance are discussed in the following sections.
Expert Judgment
Transportation planners can employ the expert judgment of transportation safety professionals in reliably assessing highway safety or predicting the future safety performance of transportation alternatives. Years of experience can help traffic safety professionals to assess the relative safety when choosing between alternative projects, strategies, and programs. Transportation planners could encourage the cooperation of safety experts through panels, consultations, and reviews and could draw on the experience of transportation safety experts to review strategies and investments in the long-range plan. These experts could also be used in evaluating alternatives for long-range project planning. Employing their assistance in the alternative design evaluation stage of project planning would be similar to conducting an informal safety audit. Safety experts may be able to identify unforeseen safety impacts of proposed transportation alternatives. They may also be able to identify the unforeseen impacts of improving the safety of one user group at the expense of another.
Predictive Modeling and the Interactive Highway Safety Design Model
Predictive modeling uses crash, traffic, and geometric data to develop a model to predict future crashes based on past performance. Transportation engineers and safety analysts develop the models by applying statistical techniques to the data. Most use a form of regression analysis to draw statistical correlations between roadway characteristics and crashes. The value of the dependent variable, crashes, is predicted as a function of a set of independent variables such as traffic volume, functional class, and roadway width. Existing crash prediction models are used for a variety of applications including identifying factors affecting transportation safety, evaluating safety at specified locations, identifying locations with higher than expected crash rates or frequencies, ranking the identified crash locations, and evaluating the application of safety countermeasures at a location.
Transportation planners and decision-makers do not commonly use crash prediction models to predict the safety performance of a project because most models are applicable only at the design level, not at the broader planning level. FHWA is currently developing the Interactive Highway Safety Design Model (IHSDM) software at the Turner-Fairbank Highway Research Center (TFHRC). The software will enable planners and highway designers to incorporate explicit consideration of safety into the highway design process. Although this model is intended for planners and highway design engineers, it extends beyond the project level, allowing them to evaluate the safety of designs under consideration. IHSDM will be a system of interactive computer modules integrated into a roadway design program. It will provide a systematic approach that will enable roadway designers and design reviewers to assess the potential safety effects of specific geometric design decisions. IHSDM will facilitate decision-making from the planning process through final design stages for both new construction and reconstruction projects. The software has a roadside safety module that will perform benefit-cost analyses of roadside design alternatives.
Rural Two-Lane Highways
An algorithm for predicting the safety performance of a rural two-lane highway was developed for incorporation into IHSDM (12). The method predicts the frequency of crashes annually on rural roadway segments and at-grade intersections on rural two-lane highways. It was developed for application by highway agencies to estimate the safety performance of an existing or proposed roadway and can be used to compare proposed geometric alternatives for a highway. The algorithm is project specific. Planners could use this model, or assist others in using this design model, to address project-specific safety considerations.
The transportation decision-maker would select a proposed roadway segment or intersection. Separate algorithms were developed for roadway segments and for three types of at-grade intersections: three-leg intersections with STOP control, four-leg intersections with STOP control, and four-leg signalized intersections. All four of the algorithms can be combined to predict the total crash experience for an entire highway corridor.
The algorithms are composed of base models and accident modification factors (AMFs). The base model is used to estimate the expected accident frequency for a specified set of nominal base conditions at a particular intersection or roadway segment. The base estimate is then adjusted with the accident modification factors that represent the safety effects of individual geometric design and traffic elements of the at-grade intersection or roadway segment. Because accident frequencies vary widely by agency, the AMFs account for differences in roadway alignment, cross section, and intersection design between sites. State or regionwide differences in climate, animal population, driver populations, accident reporting thresholds, and accident reporting practices are accounted for with a calibration procedure. After the calibration procedure is applied, the predicted crash frequency is known. For entire roadways, the predicted crash frequencies of the roadway segments and at-grade intersections that make up the roadway are summed. For planned roadways not yet constructed, the predictive process would conclude at this point. The remaining steps in the process are for existing sites when the site-specific accident history is available. For these sites, an Empirical Bayes procedure is applied to the accident-prediction algorithm and site-specific accident history.
The model was developed by combining historical accident data, regression analysis, before-and-after studies, and expert judgement to make safety predictions. This is a new approach that could potentially be adapted for similar predictive models for other roadway types.
The accident prediction algorithm could assist transportation planners in predicting the safety performance of rural two-lane highways. Incorporating the algorithm into IHSDM will increase the ease of applying the algorithm. Currently, a 13-step process for the applying the model to planned facilities is explained in the report documenting the algorithm.
Forecasting Safety: Applying Predictive Modeling to Travel Forecasting
One of the long-range responsibilities of transportation planners is travel forecasting. Travel forecasting is the process of predicting future travel demand to analyze long-range transportation alternatives. Travel demand is predicted, or forecasted, to estimate the likely transportation consequences of several transportation alternatives being considered for implementation. These alternatives could also include a "do-nothing" option.
Travel forecasting is a multi-modal process that typically consists of four-steps: trip generation, trip distribution, modal choice, and network assignment. The process uses land use and socioeconomic projections for an area as inputs to develop the impacts of the future transportation system. The outputs of travel forecasting are projected volumes, speed, origins and destinations, and mode split. The level of service can be calculated for the various modes and facilities within the transportation network based on these outputs. The level-of-service results can help planners to identify future system deficiencies and to plan and schedule capacity improvements accordingly. The process is also used to identify the environmental impacts of future transportation alternatives.
Together, travel forecasting and safety predictive modeling can be used to forecast future operational characteristics and environmental impacts of the transportation network, as well as future safety of the network. Currently, the predictive modeling tools to accomplish this kind of analysis are not available. The lack of a reliable method for estimating the safety performance of an existing or planned roadway has been identified as one of the most critical gaps in the management of highway safety. Research is focusing on creating predictive modeling tools for this purpose.
Although not available, the analysis tools and their use in travel forecasting can be envisioned. A typical long-range technical analysis process incorporating potential safety analysis tools is envisioned in Exhibit 2-4. This technical analysis could evaluate how well transportation improvements achieve the goals for an area.
Long-term analysis tools would enable planners to be proactive in formulating solutions to safety problems. The long-term analysis would be primarily a forecast of crash levels based on exposure, speed, and operating condition of the multi-modal network. This effort will therefore focus on creating a safer transportation environment through land use, transportation projects, and network planning.
To accomplish this, the associated tools should work within the current analysis process used by most planning agencies. The proposed safety tools are incorporated and are discussed in the following sections. The analysis process should evaluate and optimize both land use and proposed transportation network to achieve not only mobility and/or air-quality goals, but safety goals as well.
Exhibit 2-4
Overview of Envisioned Long-Term Technical Analysis Process Incorporating Safety
Project tool
The project tool would help planners to evaluate and formulate projects for improving the safety of system users. Considered both a long-range tool and a short-range tool, it would include a "hot-spot" evaluation component. The tool would also help planners formulate solutions by providing a reference of potential improvements to enhance safety. The output of the project-level tool would be a mix of transportation projects that could then be integrated into the TIP, and, for use in the long term, into the transportation network for metropolitan transportation plan (MTP) analysis purposes. The project-level tool would be highly useful to local jurisdictions and other implementing agencies usually charged with proposing projects to be included in the TIP or MTP. Currently, planning agencies such as SEMCOG and the Arizona DOT have developed project tools that can perform this evaluation. They are discussed in Chapter 3, Incorporating Safety Into Short-Range Planning.
Land-use tool
The land-use tool would assist planners in creating a land-use scenario for improving the safety of transportation system users. It would be most useful in long-term analysis, providing the planner with ideas about the safety benefits of different land-use scenarios. The tool should also include a reference, providing potential alternatives to enhance safety. The result of this module would be a land-use scenario to be used in the regional land-use scenario for MTP testing.
Network tool
The network tool is the most complex of the safety analysis tools represented in this report and should incorporate all users including transit, motorized and non-motorized users. The envisioned tool would have two components: the crash prediction and alternative network preparation modules.
The crash prediction tool would provide planners with the ability to take assigned transportation networks with traditional output (volume, speed, delay, volume/capacity ratios, and the level of usage by facility type) and, by using the relationships between these data elements and crashes, develop a forecasted crash level. This would provide a metric for planners to evaluate the level to which the network tested helps them achieve their safety goal.
If the network requires additional modification to optimize the safety benefits, the alternative network preparation tool should be used. This tool would include a reference providing planners with ideas to enhance the safety of the network. If changes are made, the network would need to be "fed-back" to the travel model, to re-estimate the travel demand, distribution, mode usage, and level of use on the network.
Although these planning analysis tools are not available, FHWA and other agencies are exploring their development or conducting research that will make these tools possible in the future. Recent research has focused on forming models for predicting the effects of highway design, traffic density, and land use on highway safety by studying the historical effects of various conditions on crash occurrence. The following section discusses research that eventually will lead to the development of an analysis method for forecasting the safety effects of transportation alternatives as part of the travel forecasting process.
The Relationship Between Volume and Safety
One of the main outputs of the travel forecasting process is the distribution of transportation volumes by mode. These volumes are available for all facilities modeled (for example, highways and transit lines). An analysis tool that predicts the future safety performance of a transportation network could use these volumes in the prediction.
Zhou and Sisiopiku (13) studied the relationship between volume-to-capacity (V/C) ratios and safety. The correlation between V/C ratios and crash rates follows a general U-shaped distribution; that is, crash rates are highest for low hourly volumes with a low corresponding V/C ratio. The crash rates decrease with increasing V/C ratios but then increase again as the V/C ratios increase. The researchers' findings were based on local data. Much more research is needed before the results can be generalized and applied in transportation planning.
Frantzeskakis and Iordanis (14) also studied the relationship between traffic accident rates and the V/C ratio. These researchers used 89 months of crash data from an 18 km section of interurban, four-lane undivided national highway in Greece. They found that the rates for traffic accidents were almost constant for level of service A, B, and C at non-hazardous locations for a V/C ratio of up to 0.65. The crash rates increased considerably for ratios higher than 0.65 and more than doubled when the V/C ratio was greater than 1.0. This same pattern was also observed for accident rates and V/C ratios at locations considered hazardous by the quality control technique, and when specific categories of accidents are analyzed, such as day and night, or dry and wet pavement conditions. The study was intended to explore the use of V/C ratios in traffic analysis as an alternative to volume as a measure of exposure in accident analysis. However, the findings are valuable in understanding the relationship between V/C ratio and safety.
The University of Tennessee is also involved in testing relationships between V/C ratios for differing levels of facilities and crash or accident potential. These relationships were developed in the 1970s in North Carolina and have not been tested for transferability to other areas of the United States. This effort promises to be a first step in working on the relationships needed to improve predictive safety modeling.
Challenges to Incorporating Safety Into Long-Range Planning
Planners may experience some challenges when incorporating safety into the long-range transportation planning process. Accomplishing many of the steps needed in the process is difficult. However, progress is being made. States such as Pennsylvania and Michigan are meeting these challenges to improve the safety of the transportation system. The following sections describe some of the challenges and methods for overcoming those challenges.
Balancing Safety Goals with Other Goals
Achieving the goal of improved safety may mean that another goal will not be achieved. For example, the goals of increased mobility and increased safety can often conflict. A project that increases the mobility of an area may decrease the safety. Transportation planning agencies should attempt to find a balance between the goals.
Turning Safety Goals Into Safety Actions
Although safety is often included as a goal of a long-range transportation plan, it is often not actively incorporated into long-range planning. As described previously, specifying objectives and performance measures can help to achieve the safety goal. The safety objectives aid in translating the safety goals into actions, and the performance measures ensure accountability of the process.
Competition for Limited Funding
The lack of funding can be a challenge to incorporating safety into long-range planning. Often, transportation planners must allocate limited funding between competing priorities. If safety is not identified as a priority, funds may not be allocated for it, especially for long-range projects and planning. Planners can overcome this by bolstering public support for safety. The public must be involved in the long-range planning process to understand the importance of safety in long-range planning.
Competing Needs of Users
Transportation planners must consider the safety needs of all user groups including motor vehicles, pedestrians, bicyclists, transit, and heavy vehicles. However, the safety needs of one user group may conflict with the needs of others. For example, modern roundabouts have been an increasingly popular intersection design in the United States. Research indicates that this design can reduce motor vehicle crashes and injuries at an intersection compared to a conventional signalized or stop-controlled intersection (15, 16). However, because roundabouts allow for continuous traffic movement at the intersection, this design can decrease the safety of pedestrians and bicyclists, especially for pedestrians with disabilities. In considering how various aspects of the transportation system will affect different user groups, the transportation planner could employ a citizen safety advisory committee, representative of the various transportation system users, to help account for the safety needs and identify their potential effect on one another. Transportation safety experts are another potential resource for planners.
Availability of Pedestrian and Bicycle Data
One of the challenges that transportation planners may encounter when incorporating the safety of pedestrians and bicyclists into the long-range transportation planning process is the availability of data on pedestrian and bicycle crashes, demand, and exposure. A number of studies have shown that official crash records significantly underestimate the numbers of pedestrians and bicyclists (17). In addition, reliable data on the number of pedestrians and bicycle trips is not available because of the difficulty in collecting the data. FHWA has developed a guidebook to assist planners in estimating non-motorized (pedestrians and bicyclists) travel (18).
Limitations of Predictive Modeling
Transportation engineers have developed many models to predict the occurrence of crashes. However, most of the models are not readily applicable to transportation planning. Some only predict the occurrence of crashes from existing conditions. Other models require inputs that are too detailed to be identified during the planning phase.
When used, predictive models have inherent limitations. Because the models are based on the past data, they may not be applicable outside of the jurisdiction from which they were created. Even the best predictive models may not yield accurate estimates of crash frequency, especially if some of the parameters of the input variables are outside the range of data from which the model was created. Planners would likely only use predictive models based on roadway, traffic, geometric, and land-use data. However, planners must keep in mind when applying these models that crash frequency depends on many factors-all of which may not be accounted for in the predictive model.
Long-Range Methodologies: Research on the Horizon
One of the challenges in integrating safety into the long-range planning process is the lack of accepted methodologies to predict the long-range safety performance of a facility or proposed facility. The National Cooperative Highway Research Program (NCHRP) anticipates undertaking a study to develop better predictive tools for identifying safety deficiencies and methods to address those deficiencies. The research will review existing methods of predicting future safety deficiencies as part of the long-range transportation planning processes, at both the state and MPO levels. Based on the findings, alternative methods will be evaluated. Another part of the research will evaluate land-use decisions and development patterns to enhance pedestrian safety, reduce conflicts between bicycles and other travel modes, and enhance transit rider safety. The final product of the research will be a guide to transportation planners. The guide will provide methods to predict long-range safety deficiencies of the transportation system and provide advice on the most effective countermeasures and their expected performance to incorporate into the long-range plan recommendations.
References
(1.) Regional Indicators: Measuring Our Progress to 2025, Delaware Valley Regional Planning Commission, Philadelphia, Pennsylvania, October 2000.
(2.) Alabama Statewide Transportation Plan, Alabama Department of Transportation, Montgomery, Alabama, June 2000.
(3.) PennPlan Moves!: Pennsylvania Statewide Long Range Transportation Plan, 2025, Pennsylvania Department of Transportation, Center for Program Development and Management, Harrisburg, Pennsylvania, January 2000.
(4.) PennPlan 2000 Achievement Report, Pennsylvania Department of Transportation, Center for Program Development and Management, Harrisburg, Pennsylvania, June 2001.
(5.) 2020 Florida Transportation Plan, Florida Department of Transportation, Tallahassee, Florida.
(6.) West Pikeland Comprehensive Plan Update, Chester County Planning Commission, 1999.(1.)
(7.) W.A. Leaf and D.F. Preusser, Literature Review on Vehicle Travel Speeds and Pedestrian Injuries Among Selected Racial/Ethnic Groups, NHTSA, October 1999.(2.)
(8.) Janson, B.N. and A. Rathi, Economic Feasibility of Exclusive Vehicle Facilities, Transportation Research Record 1305, National Research Council, Transportation Research Board, Washington, D.C. 1991. (3.)
(9.) Hoel, L.A. and Vidunas, J.E., Exclusive Lanes for Trucks and Passenger Vehicles on Interstate Highways in Virginia: An Economic Evaluation, Report Number FHWA/VTRC 97-R16, Virginia Transportation Research Council, Charlottesville, VA, 1997.
(10.) Exclusive Truck Lanes Approved as Part of Regional Plan, The Urban Transportation Monitor, Vol. 15, No. 8, April 27th, 2001.
(11.) Interview with Naresh Amatya, Department of Planning and Policy, Southern California Association of Governments, March 6th, 2002.
(12.) Harwood, D.W., F.M. Council, E. Hauer, W.E. Hughes, and A. Vogt, Prediction of the Expected Safety Performance of Rural Two-Lane Highways, Office of Research and Development, Federal Highway Administration, McLean, Virginia, December 2000.
(13.) Zhou, M. and V. Sisiopiku. Relationship Between Volume-to-Capacity Ratios and Accident Rates. Transportation Research Record 1581, Transportation Research Board, Washington, D.C., 1997.
(14.) Frantzeskasism J.M. and D.I. Iordanis, Volume-to-Capacity Ratio and Traffic Accidents on Interurban Four-Lane Highways in Greece. Transportation Research Record 1112, Transportation Research Board, Washington, D.C., 1987.
(15). Robinson, B.W. et al., Roundabouts: An Information Guide, U.S. Department of Transportation, Federal Highway Administration, Turner Fairbank Highway Research Center, McLean, Virginia, 2000.
(16.) R. A. Retting, B. N. Persaud, P. E. Garder, and D. Lord. "Crash and Injury Reduction Following Installation of Roundabouts in the United States." American Journal of Public Health, Vol. 91, No. 4, 2001.
(17.) Stutts, J.C. and W.H. Hunter, Police Reporting of Pedestrians and Bicyclists Treated in Hospital Emergency Rooms, Transportation Research Record, Transportation Research Board, Washington, D.C., 1998.
(18.) Schwartz, W.L., C.D. Porter, G.C. Payne, J.H. Suhrbier, P.C. Moe, and W.L. Wilkinson III, Guidebook on Methods to Estimate Non-Motorized Travel: Overview of Methods, Federal Highway Administration, Turner Fairbank Highway Research Center, McLean, VA, 1999.
