Next tonight, to some alarming close calls. Why authorium are concerned about drivers running red lights this weekend. Here's David Kerley. Reporter: You've seen it. You may have done it. Run a red... See More
Next tonight, to some alarming close calls. Why authorium are concerned about drivers running red lights this weekend. Here's David Kerley. Reporter: You've seen it. You may have done it. Run a red light. The results can be devastating, even deadly. Watch this. The yellow light. The car in the right lane stops, but four seconds after turning red, a car in the other lane runs the light. And look in the crosswalk, someone on a bike nearly hit. Red light running happens a lot, but a new study says it happens the most on Fridays, and listen to this. Between one and five in the afternoon is the worst. This weekend, memorial day, the worst holiday weekend for red light running. The worst day in the year, the Friday before labor day. What is it about these Fridays? My husband was killed on a Friday. Reporter: Melissa wandall's organization looked at 2,200 intersections in 20 states and found the Friday frequency. They think it may be that people are ready to start their weekend, get home or somewhere else. The weekends are supposed to be family filled, fun, getting out of town to do what you want to do. People need to be mindful. Reporter: And do they miss the yellow light? Those yellows average about five seconds. There is no set standard. It can vary from three to six seconds depending on the speed limit and intersection design. In the time it takes me to cross this street, nine seconds, somewhere in the country a car has run a red light. It happens in an instant. Remember that, especially on Fridays. David Kerley, ABC news, Washington.
This transcript has been automatically generated and may not be 100% accurate.