This is a common misconception, in the "traffic world" when computing the optimum cycle length for a signal, the sum of the yellow light and green light is considered as one, after the yellow time has been determined. The proper way to calculate the length of a yellow light is as such, a driver shall have sufficient time to either:
a) travel through the intersection safely, before the light turns red, or
b) safely come to a stop (b/c there's not enough time to make it though the intersection safely)
So, what exactly do I mean by 'safely' you ask... The yellow light should be long enough for a driver, who is traveling at the speed limit and within close range of the intersection, to pass safely thorough the intersection without accelerating.
Unfortunately, most traffic engineers either didn't learn this in school, or some moron thought they had a better idea to make them 1 second long. When a yellow light isn't long enough for someone to process that the light is yellow, and then make a clear decision if they can pass through the intersection safely, you get a "dilemma zone." A dilemma zone is when you can't safely travel through the light or safely stop before the light turns red (i.e. safely is not slamming on your brakes).
"a Belgian traffic researcher thinks that traffic lights that respond to local conditions could ease congestion and reduce your frustration. His method would not give you the individual power to switch the light to green. But if you were part of a group of cars approaching a red light, inexpensive traffic-flow sensors would detect your group in advance and turn the light to green. However, his system has not been adopted by any large city."
I am a traffic engineer, and traffic lights similar to what this Belgian traffic researcher describes already exist. They are called "actuated signals." They work as follows: Loops (not weight sensors, but magnetic loops) are placed in the roadway approx. 300 meters before the traffic light, then 200m, 100m, 50m and 10m. When the light is green for this path, every time a car drives over a loop(assume 300m loop), the green light time is extended long enough for the car to reach the next loop (200m), and so on and so forth until it reaches the 10m loop, where the green light is extended long enough for the car to travel safely through the intersection. Now, if the 300m loop is not reactivated every 3 seconds, the light "times-out" and will turn red once all vehicles have passed through the intersection safely (so if a vehicle is on the 100m loop, the light doesn't just turn red). Additionally, the light has a maximum green cycle time (sum of green and yellow light time), typically 58 seconds. So, if there is a never-ending stream of cars, the light doesn't remain green forever. I hope this clears things up a bit. Also, actuated signals are intended for minor arterials (major collector streets), not for principal arterials (expressways and large intersections).
"His method would not give you the individual power to switch the light to green."
Actuated signals do give you the individual power to switch the light to green.
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This is a common misconception, in the "traffic world" when computing the optimum cycle length for a signal, the sum of the yellow light and green light is considered as one, after the yellow time has been determined. The proper way to calculate the length of a yellow light is as such, a driver shall have sufficient time to either:
a) travel through the intersection safely, before the light turns red, or
b) safely come to a stop (b/c there's not enough time to make it though the intersection safely)
So, what exactly do I mean by 'safely' you ask...
The yellow light should be long enough for a driver, who is traveling at the speed limit and within close range of the intersection, to pass safely thorough the intersection without accelerating.
Unfortunately, most traffic engineers either didn't learn this in school, or some moron thought they had a better idea to make them 1 second long. When a yellow light isn't long enough for someone to process that the light is yellow, and then make a clear decision if they can pass through the intersection safely, you get a "dilemma zone." A dilemma zone is when you can't safely travel through the light or safely stop before the light turns red (i.e. safely is not slamming on your brakes).
"a Belgian traffic researcher thinks that traffic lights that respond to local conditions could ease congestion and reduce your frustration. His method would not give you the individual power to switch the light to green. But if you were part of a group of cars approaching a red light, inexpensive traffic-flow sensors would detect your group in advance and turn the light to green. However, his system has not been adopted by any large city."
I am a traffic engineer, and traffic lights similar to what this Belgian traffic researcher describes already exist. They are called "actuated signals." They work as follows: Loops (not weight sensors, but magnetic loops) are placed in the roadway approx. 300 meters before the traffic light, then 200m, 100m, 50m and 10m. When the light is green for this path, every time a car drives over a loop(assume 300m loop), the green light time is extended long enough for the car to reach the next loop (200m), and so on and so forth until it reaches the 10m loop, where the green light is extended long enough for the car to travel safely through the intersection. Now, if the 300m loop is not reactivated every 3 seconds, the light "times-out" and will turn red once all vehicles have passed through the intersection safely (so if a vehicle is on the 100m loop, the light doesn't just turn red). Additionally, the light has a maximum green cycle time (sum of green and yellow light time), typically 58 seconds. So, if there is a never-ending stream of cars, the light doesn't remain green forever. I hope this clears things up a bit. Also, actuated signals are intended for minor arterials (major collector streets), not for principal arterials (expressways and large intersections).
"His method would not give you the individual power to switch the light to green."
Actuated signals do give you the individual power to switch the light to green.