SUMMARY – with experience we tend to use more rapid ‘pre-programmed’ search patterns at intersections… these search patterns are based on prior experience and expectation… experienced drivers search for gaps at a predetermined distance from the junction… failure to search ‘backwards’ towards their vehicle can lead to detection failures when there are vehicles closer than the observed gap… the failures are rare, which leads us to believe our strategy is a good one…
We know that different objects in the visual scene will compete to attract attention. If the visual scene combines a motorcycle with a car some seconds behind it, the larger of the two objects is likely to be more salient. When the driver looks, the more salient object – the car – will draw the eyes and it’s the other vehicle that is likely to win out in the competition for attention. Crundall et all (2008) found that:
“If a motorcycle and a car are within close proximity, then a saccade made by a driver made by a driver waiting to pull out at a T-junction is likely to land closer to the car. If the two objects are [further apart] from each other… the eyes will be more likely to land directly upon the larger object.”
Durations of gaze were also analyzed. Experienced drivers made significantly longer ‘first gazes’ at cars than motorcycles. It is argued that shorter first gazes may reflect easier processing of the object, but may also reflect failure to fully process the motorcycle.
But it seems we tend to take visual short-cuts too. Langham (199?) observed
“with experience, drivers may develop shorter search times at junctions and may extract from complex traffic scenes only a minimal amount of information, based on prior expectancies about what they are likely to see.”
Langham (199?) found that when viewing video clips of approaching traffic:
“…experienced drivers appear to use ‘pre-programmed’ search patterns directed towards areas of the road environment which are informationally rich; there was little evidence of these in the eye-movements of inexperienced drivers. Experienced drivers appeared to start their search at a midpoint in the scene whist inexperienced drivers started their search nearby. One consequence of this was that experienced drivers took longer to detect motorcyclists who were nearby. (i.e. to the left of the initial point of fixation.)”
The implication is that if the experienced driver fails to move his point of fixation (ie, the cone of focused, clear, colour vision) back along the road towards his own vehicle, the driver may fail to detect the nearby motorcyclist. Believing the road to be clear, the driver makes the ‘looked but failed to see’ error and commit a ROWV. So it’s possible the error is at least partly the result of a poor search strategy.
Crundall et al (2012) also captured eye-gazes of participants and analyzed differences between novice, experienced and dual drivers (holding both car and motorcycle license) as the vehicle in which the subject was seated approached and came to a halt at a junction. When a motorcycle was approaching, both the novice and dual drivers moved their gaze back along the road towards their vehicle. But humans learn. It’s a fundamental part of being human. Learning often involves discovering shorter, quicker and most importantly, less energy-costly ways of doing something. This is likely to apply as much to driving as any other task and experienced drivers failed to search back along the road towards their vehicle.
The authors suggest this may point towards an ‘over-learned strategy’ of experienced car drivers, “encouraging drivers to search beyond a motorcycle once it has been spotted”. They further argue this over-learned strategy may “reduce chances of spotting the motorcycle at all”. By contrast, dual drivers “showed longer fixation durations on the vehicle than drivers, perhaps suggesting greater depth of processing”.
If motorcyclists have developed better strategies in terms of detecting other motorcyclists than drivers, this does not represent ‘careless behaviour’ on the part of the driver or an indication that the driver is ‘not looking properly’. Whilst studies report the absolute number of collisions that occur between motorcycles and other vehicles, or make assessments of the numbers of crashes that would be prevented were a particular preventative measure to be introduced, what is virtually never mentioned is the rate at which these collisions happen within the whole riding environment. In fact, the search strategy only very rarely breaks down for experienced drivers. When counted in terms of the percentage of potential collisions and the number of ACTUAL right-of-way violations, the proportion of near-misses and collisions is tiny compared with correct decisions not to pull out. What may be rather more useful to know is that some studies show that motorcyclists are more at risk from young, inexperienced drivers.
And because we are dealing with tiny numbers of failures amidst all the correct decisions, it’s arguable that interventions aimed at improving drivers’ abilities to detect motorcycles are unlikely to have any significant effect on the SMIDSY collision.
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Crundall, D., Clarke, D., Ward, P. and Bartle C., (2008) “Car Drivers’ Skills and Attitudes to Motorcycle Safety: A Review” Road Safety Research Report No. 85 Department for Transport: London; School of Psychology, University of Nottingham
Crundall, D., Crundall. E., Clarke, D., Shahar, A. (2012) “Why do car drivers fail to give way to motorcycles at t-junctions?”, Accident Research Unit, School of Psychology, University of Nottingham, Nottingham NG7 2RD, United Kingdom
Langham, M., P (199?) “An investigation of the role of vehicle conspicuity in the ‘Looked but failed to see’ error in driving” Thesis presented for Doctor of Philosophy, University of Sussex, School of Cognitive and Computing Sciences
Friday 23 November 2018 – minor edit for clarity
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