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Car/Motorcycle accidents possibly linked to brain miscalculation of size, distance and speed of travel

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It turns out that car drivers' habitually used phrase 'SMIDSY' (Sorry mate I didn't see you) when getting involved in accidents with motorcycles, might be more accurate and less of a hollow excuse than it at first appears. Studies by a Texas Technical University psychologist are indicating that they might not just be due to careless driving but that there may be a problem with the way car drivers actually see motorcyclists.

In a study in Current Directions in Psychological Science, Pat DeLucia says that small objects which are near can seem further away than larger, further away objects. These are the findings of studies into how the human brain perceives the size and speed of moving objects and the time until impact if they are approaching.

1 The moving object which the person is looking at is reflected on the eye's retina and the image expands as it gets nearer which gives the brain information about how close it is and the time before it reaches the viewer. This is called the optical variant.

2 The brain also uses shortcuts and operates a principle of likelihood and so assumes that if the object is larger, it is nearer and if it is smaller it is further away. This is similar to the way an artist would paint-in distant objects smaller and nearer ones larger, to convince the eyes and brains of those looking at the painting, that the picture has perspective.

“With computer simulations, we had a big, far object and small, near object approaching the viewer, where the small object would hit first,” “We wondered if people would choose the big one, based on the artist depth cue of relative size or choose the smaller one based on the more accurate optical invariant. Unexpectedly, people picked the bigger object again and again. We found people relied on rules of thumb.”

These findings indicate that the size of an object can provide the basis for car drivers miscalculation of the approaching speed and distance of, for example, a motorcycle, which is much smaller than a car.

This research seems to indicate that drivers' perception is based not simply on the evidence of their own eyes but may be using input from multiple information sources and filling in information on the size and the time of a vehicle's arrival, from assumptions about size and distance which might not be accurate.

This may affect the driver's ability to judge when a motorcycle might get to a junction or reach the car. So drivers are at risk of making poor judgments about safety and distance.

DeLucia is hoping that the US Department of Transportation will fund an education programme to educate drivers about her study and its findings to help reduce these types of accidents.
Information from Texas Technical University