Direct measurement of visual demand in bicycling

The use of mobile devices while cycling is common, but the risks caused by their use are still poorly understood. The growing number of cyclists means that the societal and economical impact of bicycle accidents will grow. In order to better understand cyclist distraction, we took the first steps to study the visual demand of cycling. Fourteen volunteers drove along a straight cycleway wearing electronically operated goggles that completely obstructed their field of view. The volunteers could make the goggles transparent for 500 ms by pushing a lever. The volunteers cycled at various speeds, trying to maximize the occlusion time but cycling in a safe and steady manner. We used a novel measure for attentional demand: the occlusion distance, referring to the distance the cyclist preferred to cycle without vision. Regardless of speed, the volunteers tended to cycle so that the occlusion distance remained almost constant for any given volunteer. This median distance was 5.8 meters, suggesting higher visual demands for cycling than for car driving. Longer occlusion distances correlated strongly with wobbliness. Cycling for long distances (>7 m) eyes away from the driving path seem to lead to unsteady cycling, which can be unsafe for other road users.