Traffic Operations and Management

Basic reliability issues are addressed in this study, which is not concerned with average travel times, but rather ways of describing travel times that reflect the uncertainty in the amount of time required to travel between two points. Some of the uncertainty is systematic, such as the normal ebb and flow of traffic within the course of a work day or season of the year. Congestion associated with this systematic uncertainty is called recurrent. Congestion due to unpredictable or unexpected events is called nonrecurrent. If every travel time observed over a highway section for a year is...

Agencies and practitioners often test innovative strategies for improving driver compliance with traffic regulations. However, in evaluating these strategies, researchers often rely on simple before-and-after methods that suffer from several flaws and that can result in misleading results and an inaccurate assessment of a strategy’s effectiveness. This paper examines these flaws, proposes a framework that avoids or corrects for them, and then uses it to analyze the effectiveness of a common strategy: installation of larger signage (at a freeway entrance ramp). The framework described in...

Advanced signal control strategies, based on real-time information on vehicles’ location, speed and characteristics as well as communication to the signal control infrastructure, can enhance mobility, safety, and the environment. Several performance measures are proposed for evaluating signal control algorithms, and procedures for estimating the performance measures from connected vehicle data are developed using statistical techniques and kinematic wave theory. A number of control strategies are developed and tested through simulation to improve mobility: queue spillback avoidance,...

We present a system that displays travel time predictions in real time on changeable message signs (CMS) in California. Using loop detector data, this system calculates predicted travel times on designated routes every five minutes. An automated process displays the current travel time predictions on the appropriate CMS’s. We demonstrate the benefits of real time travel time prediction. Historical analysis show that route decision based on CMS almost always identifies the quickest route when alternates are available. Regardless of whether alternate routes exist, prediction reduces travel time...