In many places, the light signals that tell pedestrians when to use the crosswalk have countdowns alerting them to exactly how long they have left to cross the road.
The goal of these countdowns is simple: reducing pedestrian accidents. Even though people are not supposed to start crossing the road on a flashing signal, many do. Without a timer, they could step into the street and then find that they either have to run across or hold up traffic. The countdown allows them to know just how fast they need to walk to make it in time.
The downside is that those timers also tell motorists how long until the light changes. In some studies, drivers have been observed speeding up when the timers on the cross street get low. They know they only have one or two seconds, so they'll tailgate the next car in line as they try to push through. This can cause car accidents, especially when one driver sees the timer and speeds up while the driver ahead of him or her sees the yellow light and slows down.
A solution that some have proposed is simply to change the timers to an audible countdown. That way, walkers will still be able to hear it and react appropriately, preventing those ever-dangerous pedestrian crashes, but drivers in nearby vehicles won't be able to hear it at all. They'll drive safely, without trying to rush through a light at the last second.
What all of this shows is that intersections are a very dangerous place, both for drivers and pedestrians. Those who are hurt in accidents must know their legal rights to compensation.
Source: Priceonomics, "How Timers At Traffic Lights Cause Accidents," Alex Mayyasi, accessed March 21, 2018