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'Uncommon' motorbikes reason behind accidents

Motorbike surprise Motorcyclists are more likely to be in an accident partly because they are less common on the road and drivers aren't expecting to see them, new Australian research suggests.

The study, published in the journal Attention, Perception, & Psychophysics, suggests new ways need to be found to make car drivers more familiar with motorbikes, and as a result reduce the road toll.

"Motorcyclists in general have a higher crash rate and crash risk than other road users," says Dr Vanessa Beanland, an accident research at the Australian National University's Research School of Psychology.

The leading cause of these crashes is that drivers fail to see the motorcycle, sees it too late, or misjudges the speed it's going, and its distance from them.

"They tend to not see them or think they're further away than they are, and so they turn in front of them and take out the motorcyclist," says Beanland.

"A common anecdote following crashes is the driver saying 'I looked but I didn't see the motorcyclist'."

A rare sight

While motorcycles are relatively small and their riders tend to wear dark colours, they are also less common on the roads than cars and other vehicles - a fact that Beanland and colleagues thought might contribute to accidents.

The researchers got this idea from previous research that has shown that people screening luggage at airports are worse at detecting rare items.

"Motorcyclists are only 1 per cent of traffic but they're a much larger percentage of the road toll," says Beanland, adding that in Victoria, motorcyclists make up 17 per cent of road deaths.

Beanland and colleagues at the Monash University Accident Research Centre used a driving simulator designed to look like suburban Melbourne to study the effect of motorcycle prevalence on their collision rates with cars.

Half the study participants were exposed to a stream of traffic that had many cars, a high prevalence of motorcycles and a low prevalence of buses.

The other half were exposed to a traffic stream that had a low prevalence of motorcycles and a high prevalence of buses.

Over a one-hour driving period, the participants were asked to press a button every time they saw a bus or motorcycle.

"We compared how good they were at detecting the motorcycles and the buses when they were really common compared to when they were rare," says Beanland.

A high prevalence (three per minute) of either type of vehicles resulted in drivers being better at detection compared to a low prevalence (one every eight minutes).

When there was a high prevalence of motorcycles, drivers going 60 kilometres per hour could detect motorcycles on average 51 metres further away than when there was a low prevalence.

"That's an extra three seconds of stopping time, breaking time and planning," says Beanland.

In this extra three seconds a driver could stop their car in time, when before they might have had a collision, she adds.

Similarly, drivers had an extra 4.4 seconds to react to buses in situations where they occurred more frequently.

Beanland says there is no reason why similar findings wouldn't apply to cyclists as well.

Expectations

The findings support the idea that the rarity of motorcyclists is a factor in car drivers identifying them, says Beanland.

"Some of the difficulties drivers have are based on their expectations," she says. "They effectively only see what they expect to see."

Previous research suggests that car drivers who are also riders are better at detecting motorcycles.

"We know from basic psychology research that people are better at detecting things that have personal relevance to them," says Beanland. "So making motorcycles more relevant to the general public and making them more aware of motorcycles should help."

But, she says, how to do this is a more difficult question to answer.