Drivers running red lights can and do cause some of the worst accidents that occur. Stopping people from running red lights is therefore of primary importance, most would agree. But there can’t be enough cops to have one at every intersection with traffic lights, so red-light cameras that will take a photo of every vehicle running the light and send the driver a citation by mail must be a pretty good idea, right?

Probably not. In fact, red-light cameras may be more of a symptom that a cure. A symptom of government corruption is to what I refer. Oh, come on, you say. Is everything the government does corrupt? No, not everything. Just most things. And red-light cameras are surely a sign of corruption in government. Here’s why: Red-light cameras are supposed to reduce intersection accidents. Instead, they cause more people to run the light and thereby increase intersection accidents.

How is this a sign of government corruption? It is because the officials in charge know very well that accidents will increase because it is their own actions after the cameras are installed that causes the increase. What do they do? They shorten the yellow cycle because believe it or not, with a properly-timed yellow cycle the number of citations issued by the camera will not be high enough to justify the cost of it. The main cause of red-light running is a too-short yellow cycle.

It is easy to see that if there were no yellow cycle at all every intersection would be a killing zone. Whatever the speed that an automobile is traveling it cannot stop on a dime. Some time and distance will be required to stop, and the greater the speed the greater the distance and time to stop. It should be a simple matter to calculate all that and determine the appropriate number of seconds that the light should remain yellow before going to red in a given intersection.

It turns out it isn’t that simple. Here is the standard equation for calculating the appropriate timing of the yellow light (click to enlarge):

I doubt that many politicians or bureaucrats in local government can perform the task that equation calls for. But their traffic engineers can. All that is required is to allow them to do their duty. But what politicians and bureaucrats can easily do is see that red-light cameras, done properly, don’t pay for themselves. A way to make them pay for themselves many times over is to simply ignore the equation above and arbitrarily shorten the yellow cycle.

The cities of Chatanooga, Tennessee; Dallas, Texas; Springfield, Missouri; Lubbock, Texas; Nashville, Tennessee; and Union City, California were found to have done exactly that prior to 2008. More recently, shortened yellow cycles at red-light camera controlled intersections were found in Collier County, Florida.

Does anyone believe these are the only cases of shortened yellow cycles to raise revenue?

Here is a rough approximation of the proper time the light should remain yellow before going to red in order to allow time for cars to stop, based upon the 85th percentile speed found to prevail on a particular roadway:

25 MPH — 3.0 Seconds
30 MPH — 3.5 Seconds
35 MPH — 4.0 Seconds
40 MPH — 4.5 Seconds
45 MPH — 5.0 Seconds
50 MPH — 5.5 Seconds
55 MPH — 6.0 Seconds

Following this simple approach will cost almost nothing and will reduce intersection accidents. Red light cameras are expensive and provide an irresistible temptation to politicians and bureaucrats to manipulate them for revenue, resulting in more accidents, some of them deadly.