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The Travel Model Improvement Program Newsletter

Issue 4, November 1995

The Travel Model Improvement Program is sponsored by:
U.S. Department of Transportation
Federal Highway Administration
Federal Transit Administration

Table of Contents
Freight Forecasting Conference
Planning Research Technical Support Contract Awarded
Announcing the TMIP Internet Site
Upcoming Conferences Related to TMIP
Activity-Based Forecasting Project
Track D Activities
Handbook for Incorporating Feedback in Travel Forecasting
Listing of Available Reports
TRANSIMS Travelogue

Freight Forecasting Conference

by Sandy Gaiser, New Mexico State University

Introduction

The Federal Highway Administration sponsored the Urban Goods and Freight Forecasting Conference hosted by the New Mexico State University Geography/Planning Department. The conference was held September 17-19, 1995, in Albuquerque, New Mexico. The 60 participants included representatives from both the private and public sectors. The primary purpose of the conference was the establishment of a research agenda leading to a set of improved models for urban goods and freight movement. Other objectives included: the identification of the major issues facing urban freight modeling, specification of the major characteristics of urban goods and freight movement, and the development of a list of data needs that will improve freight models.

The keynote speech was given by Kenneth Ogden, Professor of Civil Engineering from Monash University, Melbourne, Australia. After outlining the significant changes occurring in logistics management and the reasons that urban freight is an important activity and responsibility, Dr. Ogden stated, "In summary, one cannot escape the conclusion that the rapidly changing demands being placed on the freight sector mean that a policy of benign neglect is no longer a responsible one for urban transport policy makers and planners." Dr. Ogden went on to address urban goods movement forecasting and its relationship to planning.

Results and Recommendations of the Work Sessions

Following the plenary session presentations, the attendees adjourned to form smaller groups to prepare a series of recommendations. The following are examples of the small group recommendations.

Proceedings of the conference will be available in the spring of 1996. The proceedings will include text of the keynote and plenary presentations and results of the breakout sessions. Availability and ordering information will be announced in this newsletter.

Table of Contents

Planning Research Technical Support Contract Awarded

The Clean Air Act Amendments (CAAA) of 1990 and the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991 have added much in the way of research needs and demands for the Federal Highway Administration (FHWA). Issues such as air quality and congestion management have been legislated as new priorities, as have statewide and intermodal planning. Greater burdens have been placed on the forecasting capabilities of travel demand models. To proceed in the spirit of the recent legislation, it is imperative that research projects be conducted to explore the relationships existing among and within these issues, and to identify better procedures and methods for approaching them.

The Federal Highway Administration issued a solicitation to provide technical support in seven task areas:

Six consultants assembled teams composed of consulting firms and individual contractors. The teams submitted detailed proposals describing how they could support FHWA in the task areas.

As a result of this solicitation, two consulting teams were awarded contracts in September of 1995. Over the next three years, these teams will be supporting the TMIP research program and other FHWA efforts.

Teams

KPMG Peat Marwick (Prime)

Cambridge Systematics, Inc. (Prime)

Table of Contents

Announcing the TMIP Internet Site

Starting December 1, 1995, a TMIP Internet web site (http://tmip.tamu.edu/) will be available for travel demand forecasting (TDF) professionals. This web site was designed and implemented by TMIP staff and Bureau of Transportation Statistics (BTS) staff. The TMIP staff will continue to complete and expand the web site in the following year.

The web site will provide four basic services:

A TDF Clearinghouse

The clearinghouse is organized around 25 topic areas. An introductory article is being prepared for each of these topic areas. These articles will generally describe the topic, current status, ongoing research, policy considerations, and other information. Full-text documents and an extensive collection of abstracts will be available for each topic.

TMIP Information

This section includes the full text of all TMIP documents, the program description, and the TMIP staff directory. Information about the TRANSIMS project will also be included.

A TDF Course Listing

This listing will begin with information about the federal training program (both from the National Highway Institute and the National Transit Institute) With support from other organizations that offer the TDF course, this listing can be a comprehensive, with electronic links to the course sponsors.

A Communications Center

This center will offer electronic access to TMIP staff. The center will also offer locations for posting TDF questions and suggestions.

BTS involvement and expertise were a result of its development of the BTS SMART project. SMART or State and Metropolitan Analysis for Regional Transportation is an effort to link transportation professionals from around the country and facilitate the sharing of research. BTS is collecting research results and documents and storing these on the Internet and CD-ROMs. TMIP staff is now taking responsibility for topics related to travel demand forecasting. Our site will, therefore, be available through the direct address given in the title and through the BTS site.

We are very interested in adding documents or abstracts to the web site. If you or your organization has travel demand forecasting documents or abstracts which would be of interest to others in the profession, please contact Kim Fisher at (202) 366-4054 to discuss how the documents could be added to the web site.

A TDF compact disk which includes all the information currently on the web site is also being prepared. This CD-ROM will be available early in 1996. The announcement and ordering information for the CD-ROM will be included in the next newsletter.

Table of Contents

Upcoming Conferences Related to TMIP

Table of Contents

Activity-Based Forecasting Project

by Monica Francois, FHWA

The Metropolitan Washington Council of Governments (MWCOG), as part of TMIP and in cooperation with the US DOT and US EPA, engaged RDC, Inc. in a research study to investigate the feasibility of using activity-based methodologies to evaluate selected Travel Demand Management (TDM) policies. The sponsors' intent with the project was to investigate and develop the idea of activity-based forecasting in an applied setting, and to explore the approach's potential to expand the capabilities of the trip-based, four-step method in analyzing transportation policies and TDM-like strategies.

Activity-based forecasts are based on assumptions that travel demand is derived from the need to pursue, activities and that such activities are closely tied to household relationships and trip chaining. In their attempt to more rigorously treat travel behavior, activity-based approaches tend to focus on details and demand more and sometimes different data than traditional four-step methods; surveys revealing information on trip makers' preferences under alternative travel scenarios are essential to developing activity models for policy analysis.

Implementation and Testing

To perform this study using large-scale regional data, RDC, Inc. implemented a prototype of its dynamic Activity-Mobility Simulator (AMOS). The model was used in the region to replicate household responses to TDM measures, ranging from targeted premium charges for using personal vehicles (e.g., congestion pricing) to incentives for using alternatives to personal vehicles (e.g., improved pedestrian facilities).

RDC and MWCOG fed the prototype with both data available to the metropolitan area and a medium-scale survey conducted to collect stated-preference responses in the region to selected TDMs. The stated-preference survey revealed information essential to estimating AMOS' parameters, such as activity patterns inside and outside the home, daily travel patterns, detailed commute trip attributes, and demographic and socioeconomic data.

Findings

It was concluded in the study concluded that data available to a region (trip diaries, land use inventories, network travel times, etc.) can be used in implementing an activity-based approach. Moreover, the approach can develop travel demand forecasts which treat the daily travel pattern in its entirety, accounting for pattern changes and time-of-day shifts. The stated-preference questions developed for the study were also shown to produce credible results. Moreover, it was shown that by using a region's trip diary data, the prototype is capable of producing aggregate statistics of travel demand at levels comparable to trip-based, four-step models.

Overall, the results of the study indicate that activity-based approaches are viable policy and TDM evaluation tools, though they remain somewhat experimental at this stage.

Outlook on Activity-Based Models

To date there have only been very limited applications of the activity-based approach to travel demand forecasting or quantitative policy analysis. Several metropolitan areas, however, have demonstrated an interest in activity modeling, and have started to undertake activity surveys for their regions; among these are Boston, Oahu, Detroit, Dallas/Fort Worth, Raleigh/Durham, and Portland, OR. As part of TMIP, US DOT and US EPA anticipate continued exploration of the role than an activity-based approach can play in travel forecasting. The study's final report is being made available through TMIP's report series and will be announced in the upcoming newsletter.

Table of Contents

Track D Activities

A long-term transportation planning data related research program is being developed. This program is focusing on improving transportation planning data collection, analysis and use for States and MPOs. DOT staff has and will continue to solicit input from the transportation planning community to ensure that research responds to the most critical needs of the transportation planning practitioners. To establish an understanding of the current status of transportation data, a series of "QUICK-START" research efforts were undertaken. Work on those efforts is well under way. Draft versions of most project reports have been received at FHWA, and most should be available early in 1996.

Assessment of the State of the Practice vs. State of the Art

A white paper has been developed on the contemporary conditions and prospects of the data requirements for state and regional transportation programs in the context of the research objectives of Track D. This paper is based on the review and assessment of the other TMIP Tracks, the Draft Track D Program, current knowledge of the contractor, current wisdom and views of the transportation planning community, ongoing contacts and discussions between the contractor and practitioners/clients, discussions with DOT staff, and other sources. The paper will be available at the second TMIP conference and will form the basis of the discussion on future Track D projects.

Scan of Recent Travel Surveys

A draft copy of this document has been received by FHWA and is currently being reviewed. It is anticipated that the document will be available by the 1996 annual TRB meeting. Four purposes guided the development of the review:

The information for this review was gathered from telephone interviews with over 50 MPOs across the country in the fall of 1994. Questions were asked about data collection efforts carried out by the MPOs. Information was collected about the following types of surveys: household, external or vehicle intercept, panel, stated preference, visitor, transit on-board, commercial vehicle, work place, and special generator. We plan to periodically update this publication.

Scan of Recent and Current Research

A complete listing, description, and assessment (of its relevance and relationship to Track D) of current and planned research has been prepared. This listing covers surveys in their broadest definition (e.g., traditional household surveys, data from supplemental sources, roadside surveys, vehicle occupancy, on-board transit, unobtrusive methods, new data sources and needs, etc.) and what their products are expected to be. Implications for the Track D program are explicitly considered. The final comments on this report have gone to the contractor, and the final report is expected in early 1996.

Synthesis of Previous Conference Recommendations and Other "Off-the-Shelf" Research Statements

Several conferences in recent years have produced recommendations for improvements to, and research for, data collection and use in state and regional transportation programs. Other sources of research recommendations need to be accessed and evaluated. A complete and exhaustive synthesis of all pertinent recommendations for research is now being compiled, with appropriate categorization and prioritization (e.g., basic vs. applied; and near-term vs. long-term; or urgently needed vs. desired, but not necessary, etc.). An assessment of the relevance and usefulness of the research will be included. The first draft of this report is expected in the spring of 1996.

Portland, Oregon Case Study

Portland, OR has emerged as a good example of contemporary, modern-day data collection. The survey strategies used in Portland include multi-day activity diaries, in-home and out-of-home activities, full week coverage, transit usage, all household members, and trip ends geocoded to x-y coordinates for application in a GIS environment. In addition, there is close coordination and integration with other relevant databases (such as land use, parking and building permits).

Table of Contents

Handbook for Incorporating Feedback in Travel Forecasting: Thresholds, Methods, Pitfalls and Common Concerns

by Brian Gardner, FHWA

This case study will create a document that fully describes the entire data collection program for transportation planning and chronicles the steps and decisions that entered into achieving the current data collection activity in the Portland region. This document should be useful to states and MPOs considering data collection activities to support contemporary transportation planning processes. It will contain as much of the Portland "experience" as possible to assist other practitioners in developing their data collection programs.

Traditional travel forecasting methods apply a sequential, four-step model process. While this process has long produced models sufficient for many types of planning studies, it is understood that sometimes inconsistencies occur among the results of the sub-models. Regions experiencing significant traffic congestion or subject to conformity requirements are faced with the potential need to improve their travel forecasting methods to correct these inconsistencies. The use of feedback techniques to bring the sub-model results into equilibrium is an incremental improvement that fills this need.

A manual exploring the regulatory and model requirements for feedback and documenting methods for setting up these procedures has been developed by COMSIS Corporation. The need for addressing model inconsistencies is discussed, and the scope is further defined in the manual by three focus questions:

These questions are addressed through a discussion of the findings of previous research and are further refined through two case studies that examine feedback behavior, overhead, and implementation issues for multiple scenarios and feedback methods. Specific application criteria, feedback methods, and convergence criteria are also recommended.

This manual is now under review by FHWA staff and should be available in early 1996. Ordering information will be announced in the next newsletter.

Table of Contents

Listing of Available Reports

Addresses for report contacts:

Kim Fisher
c/o Federal Highway Administration
400 7th St SW, HEP-22, Room 3232
Washington, DC 20590
Phone: (202) 366-4054, Fax: (202) 366-3713

Lynette Engelke
Texas Transportation Institute
201 E. Abram Street, Suite 600
Arlington, TX 76010
Phone: (817) 277-5503, Fax: (817) 277-5439

Norman Paulhus
Technology Sharing Program
U.S. DOT
400 7th Street, SW, M-453
Washington, D.C. 20590

Table of Contents

TRANSIMS Travelogue — November 1995

TRANSIMS TRAVELOGUE describes current activities within the TRANSIMS project.

What is TRANSIMS?

The TRansportation ANalysis and SIMulation System (TRANSIMS) is one part of the multi-track Travel Model Improvement Program sponsored by the U.S. Department of Transportation, the Environmental Protection Agency, and the Department of Energy. The TRANSIMS project has been identified as a major effort to develop new, integrated transportation and air quality forecasting procedures necessary to satisfy the Intermodal Surface Transportation Efficiency Act and the Clean Air Act and its amendments.

TRANSIMS is a set of integrated analytical and simulation models and supporting databases whose development is led by the Los Alamos National Laboratory. The TRANSIMS methods deal with individual behavioral units and proceed through several steps to estimate travel. TRANSIMS predicts trips for individual households, residents and vehicles rather than for zonal aggregations of households. TRANSIMS also predicts the movement of individual loads of freight. A regional microsimulation executes the generated trips on the transportation network, modeling the individual vehicle interactions and predicting the transportation system performance. Motor vehicle emissions are estimated using traffic information produced by TRANSIMS. TRANSIMS major advantage for air quality analysis is the detail it provides regarding motor vehicle operation.

We will develop an interim operational capability (IOC) for each major TRANSIMS component. When the IOC is ready, we will complete a specific case study to confirm the IOC features, applicability, and readiness. We will complete the specific case study with the collaboration of a selected MPO staff. This approach should provide timely interaction and feedback from the TRANSIMS user community and more interim products, capabilities, and applications.

The Traffic Microsimulation is emphasized in the first IOC, with the goal of having it ready for testing early in 1996. As this IOC is developed, we are working with the selected MPO, North Central Texas Council of Governments (NCTCOG) (Dallas-Fort Worth), to identify studies that the IOC should support.

Cellular Automata Research

We examined improvements to our cellular automata (CA) methods for traffic simulation that would yield fundamental diagrams (flow vs density) more comparable to real world data while still achieving rapid computational speeds. These techniques include calculations that cycle through the vehicle objects, as is done for continuous spatial methods, instead of cycling through the grid cells as is normally done for CA methods. Because the number of vehicle objects is considerably less than the number of grid cells, the computations should be much faster, depending on the CA rule complexity.

We also examined the CA vehicle state transition rules in terms of the theoretical simulation concepts we developed earlier and feedback control systems theory. The rules interacting with the simulator procedures produce emergent local behaviors that can be interpreted formally as traditional feedback control systems theory with noise introduced at various points in the feedback control system. By tracking the vehicle states (velocities and gaps between vehicles) and their transitions, we have recast the CA methods into control theory equivalents. The vehicle controllers in interaction offer the prospect for making explicit the control rule transitions that are occurring implicitly in the CA. That would allow explicit identification of the detailed driver "behavioral models" that occur in the CA, but are not obvious.

Subsystem Development

In the June 1995 TRANSIMS TRAVELOGUE we described the overall TRANSIMS software framework and architecture. Since then we have implemented several subsystem designs. The database subsystem now supports all major functions needed for the IOC, including support for writing to the database and for schema changes. We tested the subsystem with automated test scripts that allow for future regression testing. The testing verifies that all functions work as specified and that the subsystem handles exceptional conditions gracefully. This mature subsystem will require few additional functions. We have reviewed, documented, and tested this subsystem.

The Oracle database performs well and provides common access to TRANSIMS data via either the C++ programming language or the ArcView Avenue programming language. The database subsystem will work without modification with other databases such as Sybase.

We completed the initial design of the network representation subsystem. We received input from members of the transportation planning and engineering community to assure a comprehensive, understandable representation. We implemented and tested major portions (nodes, links, unsignalized intersections, signalized intersections, parking) of the subsystem. We developed auxiliary tools for checking the network consistency, for lane connectivity generation when information is missing, and for regression testing. In subsequent iterations we added enhanced control over the creation and distribution of network objects on multiple processors and optional data items to support the Interim Planner and CA microsimulation. The current network representation describes and models the fundamental features of road networks; future enhancements will focus on functionality needed specifically for the IOC and the Dallas-Fort Worth case study. We have reviewed, documented, and tested this subsystem.

We designed and implemented the plan subsystem. This representation records a traveler's route from one place to another. The plan incorporates the notions of activities and modes. People travel from one place to another to engage in an activity at their destination. The transportation modes include the particular vehicle in which the traveler is riding, so there is a mode change when a person changes vehicles for ride sharing.

A plan is a list of trips that take a traveler from one activity to another. A trip is a list of uni-modal legs. This allows the traveler to change vehicles and transportation modes on the way from one activity to another. Finally, a uni-modal leg is a list of network links that compose the traveler's route.

We implemented the establishment subsystem. An establishment is any place where people stop to engage in an activity. It could be a house, a business, a school, or a recreational area. An establishment may have a list of activities to be accomplished by someone who is there. For example, if an establishment is a home, the establishment's activities might include going to the grocery store. The travelers in an establishment also have their own private list of activities to be accomplished.

For the IOC, available establishments include family household, non-family household, group quarters, and commercial. The establishment is identified with a specific location relative to the transportation network model. We tested the subsystem with automated test scripts that allow for future regression testing. The testing involves verifying that all functions work as specified and that the subsystem gracefully handles exceptional conditions.

We implemented a preliminary version of the activity subsystem. People travel from one establishment (or location) to another to engage in an activity. Currently, the two available activity types are distinguished by their time characteristics. In the first, an arrival time interval and a departure time interval are given. For example, a traveler might arrive at work between 8:00 and 8:15 and depart between 4:30 and 5:00. In the second, an arrival time interval and a duration interval are given. For example, a traveler might arrive at the store anytime between 10:00 AM and 4:00 PM, and shop for 30 to 40 minutes. Each activity is associated with an establishment and, hence, to the network model.

We designed the simulation output subsystem and implemented its basic functions. We began the design process with background research on parallel I/O systems. These included the PIOUS system, which integrates well with PVM, the software used to distribute the TRANSIMS processing among computer work stations. The simulation output subsystem design and architecture focuses on long-term flexibility and usability and minimizes the communication burden on the simulation network. The initial implementation collects vehicle trajectory data for use in animation and measures-of-effectiveness (MOEs) calculations. We successfully integrated the output subsystem with the distributed CA Microsimulation. Future enhancements of this subsystem will collect summarized data and improve preprocessing and indexing of data. We have reviewed, documented, and tested this subsystem.

We are developing the input editor system in conjunction with work on the editing of the network data provided by NCTCOG. The editor functions support the retrieval and storage of data from the Oracle database, validate network data, and provide some visualizing and editing of traffic networks. We will review this system's design and implementation as the development progresses.

IOC Microsimulation

We added driver logic to the micro-simulation that allows vehicles to maneuver in multi-lane traffic, follow plans, and navigate signalized intersections. We are continuing to test the subsystem integration and driver logic.

We integrated the database, network, and simulation output subsystems with the microsimulation. Integration with the network and database subsystems allowed us to perform simulation runs on sections of the NCTCOG network. Integration of the simulation output subsystem allows vehicle tracking at specified intervals as they move through the transportation network. We acquired profiling tools that help optimize the performance of CA microsimulation, parallel toolbox, and other TRANSIMS systems.

Configuration Management

All TRANSIMS software is under configuration management. We developed a general configuration management plan and selected a configuration management system, ClearCase from Atria Software, Inc. We developed ClearCase versioned object bases (configured collections of software files) for the research team microsimulation, for the network subsystem, for the database subsystem, for the planner, for the analyst toolbox, and for vehicle software. Our approach to configuration management is to observe software development practices within TRANSIMS, derive consensus on the best practices, and enhance those practices with version and configuration control.

Case Study Definition

The case study associated with the first IOC is designed to confirm the IOC features, applicability, and readiness. The study goals are two-fold: first, to demonstrate TRANSIMS on a prototype transportation problem, and second, to examine the results' sensitivities to TRANSIMS assumptions and parameters. In concert with NCTCOG we have identified a 16-square-mile region of interest (ROI) along the Lyndon B. Johnson Freeway (I-635) to focus the microsimulation analysis. From another viewpoint, the study encompasses the whole Dallas-Ft. Worth region because we have generated ten complete synthetic populations and will generate time-of-day trip plans for each household in each population. We will truncate these trip plans to the ROI for the microsimulation study.

The prototype analysis problem will examine high-occupancy vehicle lanes as an option for reducing traffic congestion. Study cases include: the existing four-lane freeway, an upgraded six-lane freeway, a six-lane freeway with two lanes designated as HOV, and the existing freeway and a barrier-separated two-HOV-lane system. Though the analysis problem focuses on the freeway system changes, we will analyze the total ROI roadway network. Thus, we will measure how the freeway system modifications affect traffic on the arterials, ramps, frontage roads, collector streets, and local streets as well as on the freeway.

Probable TRANSIMS parameters and assumptions to be studied include: network representation such as local street detail, ROI boundary conditions and distances from selected MOE roadway segments, initial conditions, driver logic and representation, trip plans, populations, etc. The number of studies is considerable so we will have to be selective in deciding which variables to include.

We are designing the study as a systems analysis in which we impose demand on the transportation system and evaluate the system's response by various MOEs. We abstract sets of demand from the synthetic demand, that is, from specific time periods in the population trip plans. Each abstracted demand is characterized by a fixed rate of vehicles entering the system and by the traffic patterns within the system. Correlated relationships, for example, congestion thresholds, between the system response and the demand characteristics can be identified with such systems analysis designs. Though the case study is designed this way, the microsimulation IOC itself will permit studies in which the system is loaded with the synthetic demand on a second-by-second basis throughout a specified time period, for example, a 24-hour period or a morning peak period.

The TRANSIMS IOC will produce vehicle position second-by-second for selected roadway segments. MOEs, such as average speed, person/vehicle time of travel, person/vehicle miles of travel, person/vehicle time of signal delay, person/vehicle time of congestion delay, variances in these measures, etc. will be derived from this output. In addition, vehicle trajectories as well as traffic flow and the previous MOEs as functions of traffic density will be plotted and compared for the various cases. We also will provide animation of the vehicle movements both for analysis and for evaluating the IOC's proper functioning.

Four-Step Process Data

Preparations for the IOC and its associated case study are giving us a taste of what to expect for TRANSIMS data availability. This first IOC relies on currently available and augmented four-step process data, particularly census data, production/attraction (PA) tables, origin/destination (OD) matrices, the transportation network data, and other information. We have received these basic four-step process data from NCTCOG for the Dallas-Fort Worth region.

TRANSIMS has an activity-based structure. We generate all travel plans from the activities assigned to households and individuals. However, a complete activity model is not necessary. In TRANSIMS trips are the means to arrive at an activity location. For example the first activity of the day may be at home, while the second is a work activity at a different location. A trip between these two locations is the natural consequence of the two activities.

This suggests that even with the TRANSIMS activity-based approach, the four-step process information can produce pseudo activities to generate trips. For example, the entries in the OD matrices or the PA tables each can be assigned two activities that will result in one trip between the two zones.

On the other hand, the network representation in the four-step process permits assumptions that are questionable within the TRANSIMS framework. For instance, in the four-step process, a collapsed network can intersect roadway segments artificially at a node and capture the overall traffic volumes adequately even though the segments may not intersect in reality. Intersections may be modeled as traffic delays. In TRANSIMS the transportation network must be represented realistically for the vehicular interactions to produce reasonable traffic behavior. However, one questions what resolution is necessary, and presumably the answer depends on the issue being studied.

For the case study we requested local street and additional road network data for the major intersections within the ROI. We participated in a meeting at NCTCOG with consultants and traffic engineers from local municipalities to discuss the data collection for the TRANSIMS network representation for the study. We were surprised to learn that the data is not readily available, though in subsequent analyses and processing of the additional road network data provided by NCTCOG, we found how painstaking it is to work with such copious data. We are working with NCTCOG to automate the network representation process. One study objective is to assess the required network detail.

For further information about the TRANSIMS program, please contact:

Dr. LaRon L. Smith
Los Alamos National Laboratory
Mail Stop F606
PO Box 1663
Los Alamos, New Mexico 87545
Phone: 505-665-1286
Fax: 505-665-0879
E-mail: llsmith@lanl.gov

Table of Contents

To subscribe to this free newsletter send an e-mail to TMIP@tamu.edu or contact Gary Thomas at (ph.) (979) 458-3263, (fax) (979) 845-6001, (mail) Gilchrist, Room 112, Texas Transportation Institute, Texas A&M University System, 3135 TAMU, College Station, TX 77843-3135