The roles of motorcyclists and car drivers in conspicuity-related motorcycle crashes

Craen, S. de; Doumen, M.; Bos, N.; Norden, Y. van
Motorcycles are vulnerable in traffic. In comparison with drivers of motorised four-wheeled vehicles, motorcyclists have a high risk of fatal or serious injury due to a crash. The main type of conflict in which a motorcyclist is injured or killed is a collision between a motorcycle and a car or van (circa 50% of the crashes). In many cases this crash is caused by the car driver failing to yield to the motorcyclist. In traffic literature these types of crashes have become known as “looked-but-failed-to-see” crashes, or “motorcycle conspicuity-related” crashes, because they are thought to be related to the low conspicuity of motorcycles. Research questions In order to develop measures to reduce conspicuity-related motorcycle crashes it is important to know the main cause of car drivers failing to notice them. Is it because motorcyclists are simply not visible? In this case measures should focus on improving conspicuity, for example by conspicuous clothing or (head)lights. But if drivers fail to notice motorcycles because they don’t expect them at junctions, measures should focus on increasing expectation and awareness among car drivers, for example in the standard car driver training. This report answers the following research questions: RQ 1 Do car drivers indeed fail to yield to motorcyclists relatively often? RQ 2 What is the role of motorcycle conspicuity (colour, size, brightness, etc) in motorcycle crashes? RQ 3 What is the role of car drivers’ expectancy, awareness and acceptance of motorcyclists in conspicuity-related motorcycle crashes? RQ 4 What is the role of motorcyclists’ behaviour (e.g. speeding) in conspicuity-related motorcycle crashes? RQ 5 On what problems should measures be focused to reduce conspicuity-related motorcycle crashes? In order to answer these research questions, a literature review and an analysis of motorcycle crashes in the Netherlands were carried out. Conclusions The majority of motorcycle crashes are crashes with a car. In these crashes, the police register the car driver as first offender more often than the motorcyclist. So in absolute numbers, many motorcycle crashes seem to be caused by car drivers (research question 1). However, when adjusted for exposure, car drivers do not crash with motorcycles more often than motorcyclists with other motorcyclists. An analysis of different crash causes at intersections indicates that, relatively speaking, car drivers fail to give priority to a motorcycle as often as to a car. In one situation motorcycles seem to be at a disadvantage compared to cars. This is when a car makes a left turn, and fails to give priority to an oncoming motorcycle. This specific type of crash occurs more often when the oncoming vehicle is a motorcycle than when it is a car. The literature review provides some answers as to why this specific scenario (car driver making a left turn) is different for an oncoming car than for an oncoming motorcycle. From the side view a motorcycle is almost as large as some cars, and because the motorcycle is in motion the car driver receives relatively much information about movement and speed. From the front-view a motorcycle is narrower than a car and has only one front light instead of two, which gives less information about speed. Regarding the second research question, there are several reasons why motorcycles are less conspicuous in traffic. Especially depth and speed perception of motorcycles are more difficult because of their small size (specifically from the front-view) compared to that of cars. In addition, studies that examined motorcycle conspicuity directly indicate that changing the appearance of a motorcycle and/or its rider does affect detection in traffic and even liability to crashes. However, research also suggests that the most important aspect of motorcycle conspicuity is contrast with the environment. Therefore, there is no clear indication of which appearance is best for conspicuity in all conditions. Furthermore, this study indicates that the expectation of car drivers play an important role in the perception of motorcycles (research question 3). There seems to be less evidence for the role of motorcycle awareness in the perception of motorcycles. There are even indications that car drivers are more cautious when they interact with a motorcycle. The fact that dual drivers (car drivers who also ride a motorcycle) are less involved in motorcycle crashes than ‘regular’ car drivers, can probably be explained by their better knowledge about motorcycling and motorcyclists’ behaviour than that they care more about motorcyclists. With respect to research question 4 we simply did not find many studies into the effect of motorcyclists’ behaviour on conspicuity. Only one in-depth analysis on motorcycle speed was found. This analysis of crashes at intersections involving a motorcyclist and another road user indicated that the initial speeds of motorcyclists involved in “looked-but-failed-to-see” crashes are significantly higher than in other types of crashes at intersections. Overall we found evidence that the perception of motorcycles is affected by conspicuity of the motorcycle and its rider as well as by the expectancy and knowledge of car drivers. Measures could therefore be focused on both sides of the perception process. Measures This report discusses several measures and their potential effectiveness to reduce conspicuity-related motorcycle crashes (Section 5.2). There is evidence that physical appearance (bright and reflective clothing) has a positive effect on crash risk. However, in different conditions (a bright day in a rural environment), dark clothing and a dark motorcycle are better. In other words, it is difficult to recommend one type/colour of clothing to improve conspicuity in all conditions. Information to motorcyclists should focus on considering the conditions in which they will use their motorcycle. In addition, because study results differ, there is need to further study the effect of clothing in a Dutch setting. The literature review and analysis of Dutch crash data both suggested that conspicuity of a motorcycle is especially difficult from the front-view. Therefore, improving frontal light configurations would seem a good way to improve motorcycle conspicuity. However, so far not much research has been done on the effect of different frontal light configurations on conspicuity. The study that we could find shows less positive results than was to be expected from the theory. Improving frontal light configurations seems promising to enhance motorcycle conspicuity, but should be further investigated. It is evident that expectancy plays a role in the perception of motorcycles. However, it is less clear if and how expectancy of motorcycles in traffic can be increased long-term. It is probably not very effective to emphasize the presence of motorcycles in driver training. If this expectancy is not confirmed by what people experience in everyday traffic, expectancy of motorcycle in traffic would probably decrease rapidly. Therefore, to increase long-term expectancy of motorcycles, measures should focus on repeated reminders regarding the presence of motorcycles on the road. With respect to changes in driver training, it would probably be more effective to teach structural procedures aimed at the detection of other road users (e.g. always look over your right shoulder before making a right turn), rather than to focus on the occasional presence of a motorcycle. Finally, it is important to realize that people, even when they are highly motivated, are limited by their capabilities; they commit errors. In this respect, measures should focus on improving the system and reducing the consequences of these errors and not on improving peoples capabilities (Wegman & Aarts, 2006). For example, ITS can be used to warn drivers that a motorcycle is approaching an intersection; or intersections can be redesigned in such a way that car drivers can make a left turn without the possibility of conflicts with oncoming traffic. Finally, motorcyclists should realize that they may not be expected or perceived by car drivers on the road. A defensive driving style could save lives.
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SWOV, Leidschendam

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