Freeway Performance Measurement System: Final Report

Problem

This report summarizes the design, operation, and implementation of PeMS (Performance Measurement System). Topics covered include the communication and software architecture of PeMS, its applications, observations of PeMS in operation, and an appendix consisting of an empirical study of congestion, capacity, and ramp metering using PeMS.

Findings

PeMS is a low-cost freeway performance measurement system for all of California. PeMS processes 2 GB/day of 30-second loop detector data in real time to produce useful information to travel network managers, traffic engineers, planners, researchers, and travelers.

PeMS utilizes an open communication and software architecture, meaning that the code used to develop the software is publicly accessible and that modifications or add-ons can easily be made to PeMS. A new district can be added to the PeMS system with six person-weeks of effort and no disruption of the district's TMC (Traffic Management Center); data from new traffic loops can be easily added as it is available. PeMS applications are accessed via a Web browser, an interface with which the majority of users will already be familiar.

PeMS is inexpensive, utilizing off-the-shelf products for communication and computation. PeMS uses data retrieved from the existing Caltrans ATM wide area network to which all districts are already connected.

PeMS benefits users in several ways:

• Caltrans managers can instantly obtain a uniform and comprehensive assessment of the performance of the freeway network.
• Caltrans traffic engineers can base their operational decisions on knowledge of the current state of the freeway network.
• Caltrans planners can examine solutions to congestion. Traffic control equipment, such as ramp-metering and changeable message signs, can be optimally placed and evaluated.
• Travelers can use PeMS via products developed by VARs (Value Added Resellers) to choose optimal travel routes.
• PeMS can serve to guide and assess intelligent transportation system (ITS).