Augmented speed enforcement system in work zone significantly reduced the number of vehicles traveling in excess of 65 mph
An automated speed enforcement system tested in a workzone on SR 152 near Los Banos, California.
Made Public Date

Augmented Speed Enforcement Project at PATH: Minimizing Hazards in Work Zones in Rural Areas

Summary Information

The Partners for Advanced Transportation Technology (PATH) developed, implemented, and field-tested an Augmented Speed Enforcement (aSE) system that will help enforce reduced speed limits in construction zones and thereby protect personnel working in the roadway. The work was conducted under a project sponsored by the United States Department of Transportation (USDOT) with collaboration from California Department of Transportation (Caltrans), California Highway Patrol (CHP), and Western Transportation Institute (WTI) of Montana State University. The project was carried out with the goal of evaluating the effect of reducing traffic speed and minimizing hazards in a work zone in the rural environment.


The system worked by performing the following steps:

  1. The speed camera system detects a traveling vehicle and determines if it is violating the speed limit. It photographs and performs automatic recognition of license plate numbers for violating vehicles.
  2. The measured speed and license plate number are transmitted to and displayed on a Changeable Message Sign (CMS) located 200-300 meters from the camera. With the aid of this enhanced feedback, drivers are advised to observe the lower speed limit while passing through the work zone.
  3. Data about speed violators, including speed, license plate number, and photograph, are transmitted, stored, and archived at a system server. This server allows remote monitoring and diagnosis of the operational status of the system as well as maintaining archives of captured and transmitted data.
  4. Data can be accessed via any web browser by authorized users who may be at a downstream location, at a range of 1,500 meters or greater, from the active work zone. This information can be displayed to police officers, for example, on a handheld device such as a tablet computer or an iPad.

The goal of the project was to evaluate the effect of reducing traffic speed and minimizing hazards in a work zone in the rural environment.


  • A great majority of the vehicles show a reduction in vehicle speed while they are in the detection range of the radar.
  • For the majority of the vehicles, the change in speed may be too small to be quantified as intentional speed reduction by drivers due to the CMS display. Nevertheless, there are still a meaningfully large number of speed reductions among all samples, which is consistent with data samples from other data sources.
  • Anecdotally, the researchers were able to observe occasional brake lights of vehicles when they approach the CMS. This also matches the noticeable numbers of significant speed reductions in data. The percentage of vehicles traveling in excess of 65 mph through the work zone was significantly reduced.
  • Based on the field test data, the percentage of vehicles traveling in excess of 65 mph was significantly reduced. For example, the summation of percentage of vehicles moving faster than 65-mph through the work zone decreased from 60.2 percent in the baseline scenario to 54.1 percent in the scenario when the PATH aSE system was in place.
  • There was a noticeable decrease of vehicles in the higher speed bins when the system was deployed.