Contributory factors

Apart from general factors such as the speed of motorised vehicles, the weight and design of motor vehicles and the lack of protection of pedestrians and cyclists (see No speed, no mass and lack of protection), factors that have also been identified as causes of pedestrian and cyclist crashes are visibility, vehicle control, and alcohol consumption.

Lack of visibility is a factor in cyclist crashes. The fact that vulnerable road users are not always very well detected in the traffic plays a part, even in daytime. This is aggravated at dusk, dawn, and night, especially when public lighting is absent or weak. The most serious problem for cyclists seems to be detection of them by drivers approaching alongside or from behind. The limited physical visibility of cyclists (linked to their vehicle - car drivers are seeking for vehicles as big as theirs) is reinforced, at least in countries when cycling is not very common, by their lack of 'social visibility': car drivers do not see cyclists because they do not expect to see any [39].

The influence of technical defects of the bicycle, the quality of the road surface, and the presence of protective devices (such as cycle seats and wheel spoke covers) has been analysed in the Netherlands. A technical cycle defect was cited as the principal cause of the crash by 7% of cyclists aged twelve years and older. In most cases, the condition of the brakes was poor [43].

Several studies have indicated that alcohol consumption is a relevant factor in crash causation. Data from Clayton & Colgan [9] suggests that two thirds of pedestrians killed between 2200 and 0800 hours in one area had been drinking, and one third had BAC levels above 150 mg/100ml; it is concluded that risk increases significantly above this BAC level. In a Dutch study in Groningen (a Northern province) dealing with the period 1993-1997, some 5-10% of pedestrians had A&E treatment in the hospital related to alcohol consumption [33].