Congestion Management and Performance Measurements Made Easy with Latest Technology
by Ben Chen, PE, PTOE
Congestion management and performance measurements are two of the primary functions for a transportation agency. A key to understanding both is travel time data. Possible uses of travel time data include:
- Quantify a region’s overall congestion level (e.g. Travel Time Index)
- Identify bottleneck areas in need of further study
- Develop future improvement projects
- Assess the benefits of transportation projects
- Calibrate and validate regional travel demand models
Travel time data can be obtained using various methods. A traditional method is to conduct travel time runs by probe vehicles equipped with GPS units. Second by second raw GPS data (vehicle speed and latitude/longitude position) are collected and compiled to obtain travel time statistics. A more cost effective method is now available to purchase a massive amount of travel time data or even raw GPS data from commercial vendors such as INRIX and TomTom.
Regardless of the data sources, the massive amount of raw GPS data poses a great challenge for an agency to manage and analyze for its use in planning and engineering. Seeking an efficient solution, Maricopa Association of Governments (MAG), the MPO for the Phoenix, Arizona region, has been working with MS2 to implement a web-based Travel Time Database System (TTDS). The system includes the following features:
- Corridor descriptions
- Corridor control/segmentation points (e.g., intersections)
- Travel time raw data (position/speed at 1-sec resolution)
- Travel time statistics calculation and reporting (e.g. regional or corridor travel time index)
- Corridor speed profile
- Corridor travel time space trajectories
- Operation/environmental improvement statistics
- Spatial maps that illustrate average speed by segment by time interval.
The MAG TTDS currently has about 8.6 million GPS records and 261 arterial corridors. The next step is to explore the opportunity of purchasing raw GPS data from a commercial vendor to provide a more complete coverage of the region in terms of geographic area and time periods. The MAG TTDS can be viewed from MAG’s official website:
http://www.azmag.gov/Transportation (go to “Transportation Data Management System” then switch to “TTDS” tab)
