Expert reveals formula for calculating time yellow light before turning red

A traffic signal expert in Minnesota (USA), known on social media as Traffic Light Doctor, has just shared how to calculate yellow light time at intersections, something that many drivers always wonder about.

Formula 1/10 speed limit

According to this expert, the actual yellow light duration is not random but is programmed based on a standard formula, taking into account the specific factors of each intersection. Specifically, a common rule is that the yellow light duration is usually equivalent to 1/10 of the speed limit in that area (in miles per hour).

The time it takes for a light to change from yellow to red has a pattern. Photo: Butler Kahn

For example, if the speed limit is 40 mph (64 km/h), the yellow light will be on for about 4 seconds. In areas with limits below 30 mph (50 km/h), the yellow light duration is usually kept to a minimum of 3 seconds.

"However, some intersections or crossroads may have different settings," Traffic Light Doctor noted. At the same time, this expert also recommends that people participating in traffic still need to comply with general regulations and rules related to stopping or going through yellow lights.

Troubleshooting when lights fail

In Ohio, according to Maher Law Firm, the law requires drivers to slow down and stop if they see a yellow light before reaching an intersection, unless they have already passed the traffic light when it turns yellow. If they cannot stop safely, drivers must look carefully as they proceed through the intersection. In fact, this law applies in many other places around the world.

Not only in Vietnam, but many drivers around the world are also confused when dealing with situations where the yellow light is on. Photo: Carexplore

American traffic websites also explain that a yellow light means "Be careful", not "Hurry up", so trying to speed up to pass a yellow light can result in a ticket from the traffic police.

In the event that a traffic light malfunctions and does not display the correct signal, the light usually flashes red, experts recommend that drivers handle the situation as they would at a stop sign. Specifically, yield to the vehicles ahead and proceed through the intersection in a sequential and safe manner.

“Even if the traffic light shows green while flashing red, stop your vehicle first to look around and only proceed when you are sure it is safe,” he said.

With this sharing, Traffic Light Doctor hopes to help traffic participants better understand the operating principles of traffic lights and make the right decisions when traveling on the road.

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Source: https://baonghean.vn/chuyen-gia-tiet-lo-cong-thuc-tinh-thoi-gian-den-vang-truoc-khi-chuyen-sang-do-10295608.html