A new study has offered an interesting explanation for something many drivers notice on the road — a slower car catching up even after being overtaken.
Published in Royal Society Open Science, the research was led by Conor Boland from Dublin City University. It uses a mathematical approach to show how traffic lights can unexpectedly change the outcome between two vehicles.
A Simple Road Scenario
The study looks at a basic situation: two cars moving at different but constant speeds. In most cases, we assume that once a faster car overtakes a slower one, it will stay ahead. However, the findings suggest that this assumption doesn’t always hold true.
The reason lies in traffic signals. Since drivers cannot predict whether they will hit a red or green light, even a faster car can end up stopping shortly after overtaking — giving the slower car a chance to catch up.
The Role of Traffic Lights
Researchers found that the chances of this happening depend on a few key factors. These include how much time the faster car gains while overtaking, the total cycle of the traffic signal, and how long the red light lasts within that cycle.
If the faster vehicle is forced to stop at a red light, the slower one can gradually close the distance, despite traveling at a lower speed.
The “Voorhees Law of Traffic”
To describe this behavior, the study introduces what it calls the “Voorhees law of traffic,” inspired by Jason Voorhees — a character famous for catching up to people no matter how fast they move.
According to this idea, if the faster car doesn’t gain much lead while overtaking, the chances of being caught up are quite high. On the other hand, a bigger lead makes it less likely for the slower car to close the gap.
More Traffic Lights, Higher Chances
The study also points out that this effect becomes more noticeable on roads with multiple traffic signals. In cities where drivers encounter several lights during a trip, the likelihood of at least one catch-up situation increases significantly.
What This Means
Beyond explaining a common driving experience, the research could be useful for improving traffic management systems. By understanding how vehicles interact with signal timings, planners may be able to design better traffic flow models.
It also suggests that these situations are not rare at all — which is why many drivers remember them so clearly.
