He thought that these signs made it much easier for the driver to prepare for a safe stop in advance of the signal changing to red. At that time this type of signal was not used where he lived.
Fast forward to today and Kate asks “When your light is green on the highway but above you the overhead warning lights have just begun should you be braking on a green light?”
The Learn to Drive Smart manual deals with this by presenting a picture of the signal and identifying it with “Signal lights ahead – prepare to stop when lights are flashing” on page 33. There is no indication given about the state of the traffic lights at the intersection ahead.
A yellow light tends to be perceived by drivers as a cautionary indication that they may either pay attention to or ignore depending on their experience and the road conditions at the time. This is generally true when the yellow light is flashing. The Motor Vehicle Act tells us that the driver of a vehicle facing the flashes of yellow light may cause it to enter the intersection and proceed only with caution, but must yield the right of way to pedestrians lawfully in the intersection or an adjacent crosswalk.
However, a solid yellow light at an intersection tells a driver to stop. There is one exception to this rule and that is when stopping for the yellow light cannot be done safely. Examples of unsafe situations would include being too close to the intersection when the yellow light illuminates or when you are being followed too closely by another vehicle.
Kate’s question really has two parts, the flashing yellow lights and the green light at the intersection. As you approach the intersection, you face the overhead warning light first and the intersection signal second. You are required to take each signal into account as you approach it, so the green light doesn’t play any part in the equation until after you have passed the yellow flashing lights.
The overhead warning lights are timed such that a driver approaching them may see them illuminate and know that the green light ahead will be yellow when they get to the intersection. The driver will be required to stop and have the time to realize it, prepare and come to a comfortable stop before the crosswalk.
The system is a good one if you are not the first driver in line when the flashing yellow lights come on. You know that the driver in front of you should stop, so you prepare to stop too. Follow the routine and you will be at a reduced risk for collision because the first driver is less likely to brake suddenly as they might be with a yellow or red light alone.
When I used an unmarked car for traffic enforcement I would watch the overhead lights come on, slow to a stop and fairly often ticket the driver behind me in the other lane who blew through without stopping. The judicial justice in traffic court was comfortable convicting that driver with only these circumstances.