Speed of the queue deceives the eye

Have you ever wondered why the traffic lane you choose always moves more slowly than the other lanes, or why the other checkout…

Have you ever wondered why the traffic lane you choose always moves more slowly than the other lanes, or why the other checkout queues at the supermarket are faster than the one you are in?

The latest scientific breakthrough means you need wonder no longer. Researchers have found that you are neither unfortunate nor logistically incompetent. You are merely the victim of an optical illusion.

Canadian researcher Mr Donald Redelmeier, supported by statisticians from Stanford, California, fitted a video camera in a car moving along a congested road. When the resulting film was shown to driving students, 70 per cent believed the next lane was moving more quickly and 65 per cent said they would change lanes if possible. However, traffic in the other lane was actually moving more slowly.

Using a computer simulation, and changing the combination of acceleration, deceleration and the number of times the driver glanced at the other lane, the illusion persisted that the other lane was moving more quickly.

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Even when both lanes were moving at the same average speed, the researchers found that vehicles within the lanes would spread out when moving fast and pack together when the speed reduced, helping to create the illusion.

So while you are busy envying motorists in other lanes, they may in fact be envying you.

Errors made changing lanes account for one in every 25 traffic accidents in Britain. No figures are available for the Republic, but a spokesman for the Dublin Transportation Office estimated the impact of lane envy was more likely to be increased stress than a rise in serious accidents.

While there was no research to suggest the presence of the lane envy illusion in Ireland, he said there was a perception among motorists in the capital that vehicle breakdowns caused more traffic chaos than they actually did. "The perception is greater than the reality," he said.

So if traffic in the adjacent lane is not really moving more quickly and if, in fact, all traffic on the same road is moving at the same speed, where does that leave the Quality Bus Corridor debate? It could send the planners back to the drawing board.