Methodologies to Measure and Quantify Transportation Management Center Benefits: Final Synthesis Report

Executive Summary

This project provides a useable means to identify and quantify Transportation Management Center (TMC) benefits. It presents direction, guidance, methodologies, and procedures to agencies associated with monitoring, evaluating, and reporting on the values and benefits of TMC operations.

The measures and methodologies developed focus on outcomes, although a number of output measures that emphasize key operations are also included. This report highlights measures used for benefit-cost analysis, including those that may be employed for freeway TMCs, traffic signal system TMCs, and corridor TMCs. Processes for freeway TMCs utilize point detector and probe detector data sources.

The following classes of measures were identified during the literature review:

• System delay.
• Safety.
• Fuel consumption.
• Throughput.
• Emissions.
• Service quality/user perceptions.
• Equity.
• Service patrol.
• Incident clearance time.
• Response to weather situations.
• Life-cycle cost.
• Database to provide motorist information.

Most of the classes contain more than one measure, and many of the measures use input data from freeway management systems (FMSs) and crash databases.

The methodologies require that the identification of a data structure that may be embraced by freeway TMCs whose software has been developed using data structures that differ from one another. Research revealed little commonality among TMCs in the spatial references used to collect and aggregate detector data. Accordingly, a reference structure that systematizes the spatial aggregation of data collected by point detector stations and probe detector locations has been introduced.

Because research has shown that most freeway TMCs use a similar data structure characterized by data storage by 5-min, 15-min, hourly, daily, and yearly periods, the findings of the project recommend this temporal structure for the freeway evaluation methodologies. Signal system measures use a 15-min span for the earliest data storage period.

This report describes the algorithms and processes used to compute many of the measures. In the case of system measures, those measures required for benefit-cost analysis, such as system-wide vehicle delay, require measurements of both volume and speed or travel time for each travel link. Other measures, such as motorist travel time and travel time reliability, require measured speed or travel time.

This report also discusses the effects of bias errors and random errors. Bias errors are most significant in conducting initial evaluations, such as before-after studies, for significant intelligent transportation system (ITS) improvements. Random errors, which are most important for year-over-year evaluations, are functions of the quantity of data collected and the size of the network under evaluation.

In addition, the report describes a methodology to obtain the benefit-cost ratio. The methodology employs annualized capital and maintenance costs and includes the following benefits:

• Reduction in private vehicle occupant system delay.
• Reduction in commercial vehicle occupant system delay.
• Reduction in goods inventory delay.
• Reduction in cost of crashes.
• Reduction in fuel cost.

Examples of agency presentations of TMC benefits are provided in this report.

The methodologies described in this report are only one element of the evaluation process. The relationship of these methodologies to the entire evaluation process is discussed.