Houston Coalition Against Red Light Cameras

HOUSTON’S RED-LIGHT CAMERAS ARE PRIMARILY MONEY-MAKERS

Laws passed in the last session of the Texas Legislature red-light camera bills submitted by Senator Corona (SB 125 and 1199) that added legitimacy to Houston’s red-light camera scam by splitting the revenues thus raised between the state and the city. Rep. Jim Murphy seconded this travesty that resembles a bunch of thieves arguing over how to divide the loot.

Here are four points against red-light cameras that are being ignored by the City of Houston:

1. It has been shown that 85% of red light violations occur in less than two seconds after the light has changed from amber to red.  I believe the primary cause of these violations is inaccuracy on the part of most drivers to properly guess both time and distance from the intersection when the light changes. 

At 35 MPH the amber period is supposed to be 3.57 seconds. A driver whose vehicle is 183.1 feet from the intersection when the light changes from green to amber has one second to gently apply the brakes and bring his or her vehicle to a normal (decelerating at 10 feet per second per second) stop. A driver whose vehicle is less than this distance when the light turns amber should continue at 35 MPH because the light will still be amber when he or she reaches the intersection and an increased stopping rate also increases the risk of a rear end collision.

According to Sergeant Muench of the Houston Police Department only a 0.1 second period is allowed for the light to change from amber to red. After that, a driver whose vehicle enters the intersection is deemed to be in violation of the red light. At 35 MPH, 0.2 seconds equals one foot of distance. In other words, if you misjudge your distance by one foot (183.1 + 1) and you continue at 35 MPH when the light turns amber, your mistake will cost you $75. If in doubt the City of Houston wants you to either: slam on your brakes, or budget for a $75 expense in the near future. And, if you guess your distance correctly this time, you get a chance to guess again at the next red-light camera intersection. What a nice game!

2. It has been proven that an increase in rear-end collisions takes place soon after photo enforcement is implemented.

3. At standard eight-way intersections it is very unlikely that a t-bone collision will occur within two seconds after the light turns red.  Stopped vehicles can not accelerate fast enough for this to be a common accident.  Most t-bone collisions are caused by drivers who are completely oblivious to a red light which has been illuminated for more than two seconds. 

 A notable exception to Point 3 occurs where the crossing street is one-way and has synchronized lights that provide for rolling greens. This permits vehicles on the one-way street to proceed through numerous intersections without stopping.  In these cases it is possible for a t-bone collision to take place within two seconds after the light change; however only few of the present 70 cameras in Houston are located at these types of intersections.

4. I have proposed a simple solution to the Houston City Council that will end the $75 guessing game being imposed upon Houston drivers.  My proposal calls for a safe stopping distance line to be placed across the approach to all photo enforced traffic lights.  This line would indicate to drivers when a traffic light changes from green to amber whether it was safe to proceed through the intersection at the speed limit without violating the red light; or to come to a normal gentle stop.  My proposal has so far been totally ignored.

It has been suggested that a count-down timer displayed alongside the traffic light will help drivers avoid running the red light. That will only answer half of the question. The driver must still estimate the remaining stopping distance. The yellow stopping distance line answers both the time and distance question in a very inexpensive and thorough fashion. It provides a clear and cheap solution to the driver’s dilemma when a green light turns amber. If a driver sees both an amber light and the yellow stopping distance line he or she should come to a normal stop at the intersection. If the diver is past the yellow stopping distance line when the light turns amber he or she should continue at the speed limit through the intersection and be confident that he or she will not violate the red light.

A count-down timer will assist those drivers whom are approaching the intersection at speeds below the speed limit to more accurately make the stop or go decision. Unfortunately the powers that be do not at all appear to be interested in these two profit reducing measures.

H. F. Van Der Grinten

Amber Time and Stopping Distance

Amber times at all camera enforced traffic lights in Houston are supposed to be at a minimum that is determined by the following formula:

                     where,

                     Y = yellow interval duration, s;

                     d_r = deceleration rate, use 10 ft/s²;

                     g = gravitational acceleration, use 32.2ft/s²;

                     G_r = approach grade, ft/ft;

                     T_pr = driver perception-reaction time, use 1.0 s; and

                     V_a = 85th percentile approach speed, ft/s.

“Eighty-fifth percentile speed” means the speed at or below which 85 percent of the motorists drive on a section of road for which speeds were measured. This is supposed to be the posted speed limit where the traffic light is located.

This table shows the numbers which go with the above accepted formula assuming a level approach. Speeds below 30 MPH are not shown because the minimum permitted amber time is three seconds. 

The stopping distance is also the stop or go decision point when the amber light is illuminated. At this time and distance a vehicle traveling at the given speed limit will arrive at the intersection at the moment the red light is fully illuminated. 

For example, at 45 MPH a driver whose vehicle is no more than 283.8 feet from the intersection when the light turns amber may continue towards the intersection without violating the red light. If the same driver is exactly at this distance when the light turns amber and he or she elects to stop, one second is allowed to apply the brakes and a gentle stopping rate of ten feet per second per second will bring the vehicle to a full stop in 7.60 seconds at the intersection stopping line. The full stop will occur under these conditions 3.30 seconds after the light turns red.