Assessing Automated Speed Enforcement in California

Speeding is known to be related to a significant portion of highway collisions. As part of the efforts to seek safety improvements of the California highway network, the California
Department of Transportation (Caltrans) is exploring the implementation issues of automated speed enforcement (ASE). This report provides an overview of Task Order 6212 undertaken by
California PATH to assess various issues associated with ASE systems. An ASE system designed for use in work zones was acquired and tested in several field experimental sites, along with several other commercially-off-the-shelf traffic monitoring devices. The objective of the study is to examine the field performance of the equipment in a real-world setting, when evaluated against other comparable traffic devices. The results from the field experiments revealed that traffic speed measurements are likely to yield discrepancies. For considerations of future deployment of ASE, the technologies can be expected to be advanced further. Since all types of sensing devices are susceptible to certain levels of interference and noises in the field, a consistent and robust method of verification and calibration for sensors used for ASE will be essential. From the design point of view, extra measures or techniques can be taken to ensure the robustness and accuracy of ASE systems. The assessment of technical performance of ASE as carried out in this project can provide insights in the process of validating functional characteristics and seeking performance enhancements. The outcome of this study, in conjunction with the experience and knowledge gained by other agencies in their development and implementation of work-zone and general ASE systems, will offer valuable support for future ASE implementation.