Red Light Cameras

Why are red-light cameras needed?

Intersection crashes resulting from red-light running are a serious safety problem. Based on information from the U.S. Department of Transportation and the Insurance Institute for Highway Safety, more than 900 people are killed and over 200,000 injured in the United States each year by this driver behavior. About half of the deaths are pedestrians and occupants in other vehicles who are hit by the red light runners.

How do they work?

Sensors in the roadway are connected to the red light camera and the traffic light controller. The camera is activated only when a vehicle enters the intersection after the light turns red. In North Carolina, the back of the violator’s car showing the license tag, not the occupants, is photographed twice to assure a violation has occurred. In a few states, the infraction is driver specific as opposed to vehicle specific, and in this case, the driver is photographed. The device also records the date, time of day, time the light has been red, and the length of time elapsed between the two photographs taken.

Representatives of local law enforcement agencies and technical representatives of the vendors who manufacture and provide service for the camera equipment review the photos before citations are issued.

Do they work?

Yes, red-light cameras reduce both red-light violations and right-angle or “T-bone” crashes due to red-light running. In Charlotte, NC, red-light running violations were reduced by more than 70 percent during the first year of operation.

The Federal Highway Administration has completed an extensive analysis of red-light camera sites across the United States. They analyzed over 130 red-light camera intersections across the country, including Charlotte, and found that the average number of right-angle or “T-bone” crashes went down 25 percent after cameras were installed.

Do red-light cameras cause an increase in rear-end collisions?

Yes, the FHWA study found that the average number of rear-end crashes went up 15 percent – but it is very important to put that into perspective – while rear-ends do increase, the overall crash harm to the victims is reduced with the installation of red-light cameras. Right-angle crashes are simply much more dangerous than rear-end collisions.

It should also be stated that this increase is not surprising. When a new signal is installed on a roadway, the same pattern is seen – the more severe angle crashes are decreased while the less severe rear-end crashes usually increase to some extent.

Why did the analysis use a measurement of harm as opposed to sheer number of crashes?

Since the angle and rear-end crashes are of different severities, you must combine both the change in frequency with differences in severity in the analysis. This is why looking at either percent changes in angles vs. rear-ends, or just at changes in total crash numbers is not correct.

How was crash harm calculated?

Each crash was assigned an economic cost based on the crash type and injury level. By comparing the total angle and rear-end crash costs after the treatment to what would have been expected without the treatment, the researchers found that the decrease in crash harm due to the angle crashes was greater than the increase in crash harm from rear-end crashes. The study estimated the safety benefit to be approximately $39,000 per treated intersection per year.

Originally posted on UNC.