How Does It Work?

In an effort to reduce collisions and make City streets safer, Daly City implemented its new red light camera enforcement program on March 11, 2008, cameras and sensors monitor the city’s highest-risk intersection approaches.

At its very basic level, the system is a series of cameras and flashes controlled by a computer, which determines when to capture images based on the speed of a violating vehicle. The system is only “armed” during the red phase of the cycle, which eliminates the possibility of a non violating capture. Sounds futuristic doesn’t it? However, in reality these types of systems have been around for a very long time. The first systems were introduced in the 1960’s. Back then, they used regular or “wet film”--much like a regular 35mm camera.

Today’s systems have joined the computer age and utilize full digital technology, making them reliable, accurate and easy to maintain. Most red light camera systems operate from three very simple principles; detection, calculation and actuation. The system must first detect that a violation is about to occur. This done by induction loop technology, radar or video detection. After having detected a violation the system must then calculate the optimum timing for capturing the violation sequence and then finally, the system must capture the violation with high resolution cameras and video.

Red Light Camera how it works


Beginning with the top image (No Violation), we see that the light is in the red phase and a vehicle is approaching the detection system. The second image (Pre-Violation) shows the vehicle crossing the detection device while the light is red. This causes the first image to be created, what we call the “pre-violation” image. It will show the vehicle clearly behind the violation line and the traffic signal in the red phase. If the vehicle were to stop and remain there no violation would take place. The next image (Plate Shot) illustrated is termed the plate image. This image is taken from the rear of the vehicle in order to capture the license plate information for a DMV inquiry. At this point, a violation has occurred because the vehicle has now crossed the violation line during the red phase. The next image (Face Shot) is termed the “face image”. This captures the driver’s face behind the wheel of the violating vehicle. In California, the driver must be identified in order to issue a valid traffic citation. Finally, the last image (Post Violation) taken is called the “post violation” image. It shows that the vehicle did in fact continue on through the intersection against the red light. Now along with the four digital still images, a 12 second video loop is captured displaying the entire capture sequence. There are 6 seconds of pre-violation video and 6 seconds of post violation video.

The ultimate goal of the Daly City Police Department is to modify the behavior of drivers in order to make our streets safer. This effort involves not only the police department, who is charged with enforcing our traffic laws but also the city traffic engineers, who constantly review current traffic patterns and look for solutions to improve not only traffic flow but safety as well. With resources stretched to their limits, many cities have begun to look to technology to assist and supplement their safety efforts. Red light camera programs are only one method that can assist in the reduction of violations and crashes. Daly City is committed to this goal through education, the application of technology and a commitment to provide our citizens with safer and more efficient travel.

Prior to commencing our automated enforcement program, Daly City undertook a study of statistical information regarding collision and violation data. The study took over a year. After data was collected and analyzed, non-enforcement solutions were looked at and applied where applicable. This included something as small as repainting crosswalk markings and verifying yellow light timings to comprehensive traffic flow studies to determine the need and application of automated enforcement. The decision was made to implement automated enforcement and a well defined governed process began.

Automated enforcement systems are well regulated by state law and have many safeguards that have been legislated in order to give the public a high level of confidence in their application. When a violation is captured, all data is reviewed by the program administrator before a citation is issued. Daly City Police will be happy to answer any questions regarding our program and how it operates.