Aggressive and timid drivers cause all that traffic jam

LONDON - Motorists who are too aggressive or too timid cause traffic snarls on busy roads.

Such snarls might be caused by an accident, a bottleneck, or lane changing cars, but it is how the drivers in the cars behind react that brings traffic to a standstill.

Researchers say aggressive motorists, who drive too fast and too close to the vehicle in front, or timid motorists, who leave too big a gap, send a “wave of deceleration” backwards down the road until traffic grinds to a stop.

Such behaviour leads to the stop-start traffic jams which infuriate, the Telegraph reported.

Researcher Jorge Laval, from the Georgia Institute of Technology in Atlanta, US, said it was important to understand what causes the jams, according to the journal Philosophical Transactions of the Royal Society.

“Stop and go driving is a nuisance for motorists throughout the world. Not only does it increase fuel consumption and emissions, but it also imposes safety hazards,” he said.

Laval, who worked with colleagues at the University of Lyon in France, found that when drivers changed their speed, they caused drivers further back to change their speed too. The change in speed passed like a wave, backwards through the traffic.

If all the drivers behaved the same way, traffic would not come to a halt. But the researchers found that in real life situations, the behaviour of aggressive and timid drivers led to the slowdown getting worse.

The scientists found that timid drivers had the biggest impact because they “shied away” when the car in front started slowing down, and deliberately started driving even more slowly to increase the gap between them. This led to cars further behind going more slowly.

Aggressive drivers also caused speed to drop because they braked hard at the last moment to avoid driving into the car in front. They then had to drive more slowly to open up a space again.