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To purchase any of the Mobility Monitoring Program research reports, contact:

TTI Publications Dept.
(979) 458-0481
sales@ttimail.tamu.edu

For more information about the Mobility Monitoring Program, contact:

Shawn Turner, TTI
(979) 845-8829
shawn-turner@tamu.edu

Tim Lomax, TTI
(979) 845-9960
t-lomax@tamu.edu

Richard Margiotta, Cambridge Systematics, Inc.
(865) 670-8516
ram@camsys.com

Mobility Monitoring Program

The Mobility Monitoring Program is sponsored by the Federal Highway Administration, Office of Operations.

Program Objectives

The Mobility Monitoring Program has the following objectives:

  1. Monitor mobility and reliability trends for FHWA performance monitoring purposes using archived traffic operations data.
  2. Provide "proof of concept" and technical assistance to foster local/regional performance monitoring programs and the supporting data collection and archives.

The most recent report includes an analysis of freeway mobility and reliability trends in 2003 for 29 cities. An annual summary report contains a summary of the methods and results, and individual appendices contain more detailed performance information for each city. These reports also contain trend information from earlier years (as early as 2000 for some cities) where that data has been made available.

Data Source

The Mobility Monitoring Program uses a different data source than the Urban Mobility Report. The Mobility Monitoring Program gathers detailed traffic operations data that have been collected and archived by transportation management centers. The data used by the Mobility Monitoring Program have the following characteristics:

  • Very detailed: the data vary from 20-second-by-lane to 15-minutes-by-direction, for all days of the year.
  • Most congested freeways: the data are typically collected by sensors on the most congested freeways in an urban area.
  • Point-based sensors: the data are typically collected by sensors that measure spot speeds and traffic volumes and are spaced about ˝-mile apart. Thus point-to-point travel times are estimated.
  • Computer-intensive processing: On average, a typical city’s data includes more than 300 million data records and requires 20 GB of storage space (about 30 CD-ROMs or 5 DVDs).

Measures Used

The following describes several performance measures reported in the Mobility Monitoring Program. More detailed descriptions and calculation procedures can be found in the annual summary report.

Mobility Measures

Travel Time Index: ratio of average peak travel time to an off-peak (free-flow) standard, in this case 60 mph for freeways. For example, a value of 1.20 means that average peak travel times are 20% longer than off-peak travel times.

Percent of Congested Travel: the congested vehicle-miles of travel divided by total vehicle-miles of travel. A relative measure of the amount of travel affected by congestion.

Reliability Measures

Buffer Index: the extra time (buffer) needed to ensure on-time arrival for most trips. For example, a value of 40% means that a traveler should budget an additional 8 minute buffer for a 20-minute average peak trip time to ensure 95% on-time arrival.

Planning Time Index: Statistically defined as the 95th percentile Travel Time Index, this measure also represents the extra time most travelers include when planning peak period trips. For example, a value of 1.60 means that travelers plan for an additional 60% travel time above the off-peak travel times to ensure 95% on-time arrival.

Data Quality Measures

In addition to these measures, the Mobility Monitoring Program reports on the quality of data used for the mobility and reliability measures. The following data quality measures are reported:

Completeness: Reported as percent complete, this measure compares the amount of data available for analysis to the amount of data that should be available based on data sampling rates and active sensor configurations. For example, a value of 90% complete means that only 90% of the total possible data records were available for analysis purposes.

Validity: Reported as percent valid data, this measures reports the percent of data that passes acceptance criteria (e.g., valid value checks based on traffic flow properties).

Coverage: Reported as the percent coverage, this measure describes the degree to which a sample accurately represents the whole of that which is to be measured. Percent coverage is reported for roadway mileage and vehicle-miles of travel. For example, a city may have 25% of their freeways instrumented with sensors. These same sensors may measure 30% of the freeway vehicle-miles of travel.

Information About:

A Cooperative Study by the Texas Transportation Institute and Cambridge Systematics, Inc.

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