As of October 1, 2016, the SWUTC concluded its 28 years of operation and is no longer an active center of the Texas A&M Transportation Institute. The archived SWUTC website remains available here.

You are here: Home / Research / SWUTC Completed Research / 161304

161304

SWUTC Research Project Description

How do Travelers Perceive and Value Travel Time Reliability

University:  Texas A&M University

Principal Investigator:
Mark Burris
Texas Transportation Institute
(979) 845-9875

Project Monitor:
Xiaozheng He
NEXTRANS Center
Purdue University

Funding Source:  State of Texas General Revenue Funds

Total Project Cost: $45,000

Project Number:  161304

Date Started: 11/1/12

Estimated Completion Date:  10/31/13

Project Summary

Project Abstract:
The value of travel time savings (VTTS) and value of travel time reliability (VOR) are two fundamental factors influencing travel behavior and demand. Although, the importance of VOR is appreciated, no definitive method of quantifying and estimating VOR exist and no definitive value of reliability exists. This research aims to understand and model how travelers behave when given a choice between tolled (and reliable) and untolled (but, often congested) lanes on a daily basis by using an extensive dataset of Katy freeway travelers. Through this study we want to (i) obtain a value of travel time reliability i.e. the monetary value travelers place on improving the reliability of their travel time (ii) Estimate a value of time separate from the value of travel time reliability, two variables which are generally linked together and (iii) Gain and understanding of how travelers view reliability i.e. what measure of reliability most closely represents how travelers perceive reliability. We intend to use statistical analysis tools and our expertise in the field of travel behavior to reach these predetermined goals. This study has the potential to forward our understanding of the concept of VOR, guide future research in this area and help improve related aspects of the transportation planning and decision making process.

Project Objectives:
The emphasis of this study is to understand and model how travelers behave when given a choice between tolled (and reliable) and untolled (but, often congested) lanes on a daily basis and in the process achieve the following objectives:

  1. The first and the most important is to obtain a value of travel time reliability. This is the monetary value travelers place on improving the reliability (decreasing the variability) of their travel time. As noted above, there is considerable national effort to add travel time reliability in the planning process so it is essential to be able to define the value of travel time reliability.
  2. Estimate a value of travel time that is separate from the value of travel time reliability. These two values are difficult to separate as faster travel time is almost always linked with more reliable travel time and it becomes difficult to know how much the traveler is willing to pay for each component. Our dataset would enable us to estimate value of travel time separately from value of travel time reliability and therefore understand how much the traveler is willing to pay for each component.
  3. To gain an understanding of how travelers view reliability. Is it what happened on their most recent trip? Or more of an overall view of several recent trips? We would use different interpretations of travel time reliability and determine which one more accurately represents how travelers perceive travel time reliability. For agencies trying to incorporate reliability into their planning process this provides much needed details on what data needs to be collected on the reliability of their facilities.

Task Descriptions:
Task 1:  Literature Review:
A systematic review of the literature on travel behavior, travel time and travel time reliability, and more specifically on value of time and value of travel time reliability will be carried out.

Task 2:  Data Manipulation and Analysis:
In this step, data available would be first checked for errors. Due to the large amount of data, a sample of the data would then be selected for analysis. The sample dataset would be manipulated for modeling travel behavior.

Task 3:  Generation of Models:
Using different definitions of travel time reliability and recent reliability we will develop models and see which one more accurately represents traveler’s choices on the lanes. In this process, we will also determine the value of travel time reliability as perceived by the travelers.

Task 4:  Validation:
We will choose a new sample and redo our analysis to validate are results and our models.

Task 5:  Final Report:
The research team will prepare a final report documenting the literature, methodology, data used, and the results of this research.

Implementation of Research Outcomes:
The literature on the value of passenger travel time is extensive and well developed but research attempting to quantify value of travel time reliability (VOR) is relatively new. Lack of relevant empirical data has hampered travel time reliability studies. Stated and revealed preference surveys have been the primary tools used to understand the concept. But, these methodologies have shortcomings that have been widely noted in the literature. This research uses a novel approach to try to understand travel time reliability using empirical data of travelers from the Katy freeway. The use of empirical data enables researchers to overcome most of the shortcomings of the existing techniques used such as perception errors. Through this research it has been found that the understanding of travel time reliability is far more complex than what has been reported in existing research. Moreover, common measures of variability such as standard deviation of travel are not representative of how travelers perceive travel time reliability.

Products developed by this research include:

Presentation:  How do Travelers Perceive and Value Travel Time Reliability – Initial Findings, Mark Burris, presented at the 13th Chinese Overseas Transportation Association (COTA) International Conference of Transportation Professionals, Shenzhen, China, August 13-16, 2013.

Technique Developed:  An algorithm (technique) was developed to identify individual trips and related trip attributes on a freeway using automated vehicle identification (AVI) records and tolling information from the sensors on the freeway.  The technique was subsequently used for a study on Atlanta I-85 Express Lanes, which have similar AVI and toll sensors.  The results of that research produced a presentation at the 2014 Annual Transportation Research Board Meeting.  In addition, the techniques, and code developed by this research are being shared with 4 other students for their research.  It will form the data foundation for 3 Masters’ theses and 1 PhD dissertation.

Anticipated Presentation:  Annual Transportation Research Board Meeting, January 2015.

Impacts/Benefits of Implementation:
The focus of the project was to study existing travel behavior on a freeway with both tolled and free lanes. The research provides a better understanding of how travelers make decisions and choose between different options. This knowledge can be used to make better-informed infrastructure funding decisions and improve the existing transportation system. On the service provider side, this knowledge can help better price existing infrastructure to reduce overall travel time, (un)reliability and optimize revenue generation. On the consumer (traveler) side, better understanding of the system would enable travelers to make better use of the existing facilities and maximize their own utility. Overall, this would lead to improved social, economic and environmental conditions.

Web Links:
Final Technical Report