Whenever I am driving I try to speed through the light when it is yellow and it is always stressful trying to get through before it becomes red. Street crossing lights have a countdown number that tells the walker how long until the light changes. Why isn't a similar thing implemented on traffic lights? enter image description here

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    We in India have Vice Versa :) Commented Jun 2, 2017 at 4:22
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    There are a traffic lights in the Netherlands that count down (3, 2, 1) until the lights turn green. My experience is that it turns people in racing drivers. They speed away when the timer hits zero. Often times people even jump the timer. I think it's dangerous. Maybe that's why. Commented Jun 2, 2017 at 7:42
  • In Croatia, some traffic-lights have this feature. Commented Jun 2, 2017 at 12:51
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    Yellow light laws vary from state-to-state (assuming you're in the USA). In some cases it is illegal to pass through a yellow light unless you are already in the intersection or cannot "safely stop". Regardless of the specifics of your local laws there is really no need for a countdown... because you shouldn't be speeding through a yellow! The point of yellow is not "better get moving", it's "light is getting ready to change, better stop now if I can". Commented Jun 2, 2017 at 15:41

2 Answers 2


Introduces Calculation, Gamification, and Additional Cognitive Load to the Interaction

In addition to the practical factors presented by Michael Lai, I suggest a key reason for not including this feature is that it introduces potentially negative factors to the interaction.

Ideal User Reaction

"Light changing. Red soon. Prepare to stop".

Potential User Reaction

"Light changing. 25 seconds. Car in front not slowing. Hmmm. 23 seconds. 200ft to intersection. Can I make this? 20 seconds..."

This isn't to suggest that this type of reaction isn't possible with the typical simple color system, but I'd argue that the 'Ideal User Reaction' (above) is more likely to result from a simple color system.

The additional thinking time and cognitive load of a system that introduces timing, when spread across all levels of driving ability, aggressiveness, competitiveness, and risk adversity, would likely result in a net negative affect on driving behavior.

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    It is hard to read those numerals, and the effort to see a small object off the side of the driving path takes one's eyes away from what they are supposed to be looking at: the road. We could consider why speedometers (and clocks) made a brief foray in to being digital, then all went swiftly back to analog: speed and time are analog concepts, and digits mean nothing at all visually. If anything, the remaining time should be a visually obvious linear scale, like a bar-graph decreasing. But it still would require too much cognitive load, which we cannot spare while driving a two-ton object.
    – user67695
    Commented Jun 8, 2017 at 14:26
  • What about adding timers only for the red lights?
    – Calmarius
    Commented Feb 9, 2019 at 23:57

Actually there are examples of this in different countries, or at least I have seen it in Shanghai before.

There are a lot of reasons behind whether systems like this can be implemented or not, but a traffic engineer might provide a more accurate answer. But in general these are the considerations that I know:

  • Cost: probably the number one consideration since these devices are quite expensive to install and maintain
  • Feasibility: traffic regulations and rules may prevent the logical or practical implementation of these systems
  • Impact: you could argue whether pedestrians just end up modifying their behaviour instead of becoming more safety conscious, and whether drivers would end up just modifying their behaviour as well.
  • When things are safety related, they have to be dead simple, or else people end up... dead.
    – user67695
    Commented Jun 8, 2017 at 14:28

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