AN EMPIRICAL ASSESSMENT OF TRAFFIC OPERATIONS

摘要

In its draft Transportation Management Systems (TMS) Master Plan (System Metrics Group, Inc., 2003), Caltrans proposes an action plan to improve incident management, traffic control, and traveler information. Central to the plan is its reliance on specific performance indicators to serve "as monitoring and evaluation tools, and establish an accountability framework for the implementation of planned TMS improvements." Caltrans has invested significant resources to develop a performance measurement system (PeMS). This paper illustrates why PeMS became a major source of 'performance indicators' and suggestions for performance targets. The paper uses PeMS data to study freeway congestion from six different perspectives, ranging from identification of bottlenecks to evaluating the benefits of ramp metering and the effectiveness of HOV lanes. In each study, the aim is to measure the severity of congestion and reveal the opportunity for improvement. The approach is to argue on the basis of statistical models that the data are used to estimate. Qualitatively of course the models are inspired by prior theory, but the emphasis is always on quantitative conclusions. Partly motivated by the success of PeMS, some universities and DoTs are developing small-scale prototypes of PeMS-like systems. These efforts will have a small impact until state DoTs invest in data collection infrastructure. The availability of these data will shift DoT focus from construction to operations improvements. Academic research, too, will change as it exploits opportunities opened up by access to large-scale data sets and pays more attention to questions that address the opportunities for operations improvements and conducting experiments that demonstrate improvements.