Abstract
The most frequent bicycle accident type at roundabouts has been shown to be between the entering driver and the circulating cyclist. On the basis of unobtrusive video recordings, in this study we show how the behavior of drivers entering the roundabout depends on the traffic situation on it. A test (stunt) cyclist was provided to create well-controlled conflict situations during the recordings. Drivers' adjustments to the test cyclist were measured in terms of approaching speed, head movements, and the manner in which they yielded to the test cyclist approaching the joint-conflict point at the bicycle crossing on a collision course, from either the left or the right. Six roundabouts in Finland, Sweden, and Denmark were included in the study, representing different roundabout layouts. The main differences were in the size of the central island and the location of the bicycle crossing. The approaching speed of the cars was lower at the roundabouts with large central islands (40-m diameter) than at those with smaller central islands (13-m-16-m diameter) that allow drivers to use a more direct driving path. The majority of drivers adjusted their visual search pattern adequately, even when the cyclist came unexpectedly from the right (the opposite direction from the motorized traffic). However, 7% to 15% of the drivers did not look at all at the cyclist when he was approaching from the right. A higher approach speed was a contributory factor in terms of not looking to the right, supporting the notion that high speed makes drivers pay attention to the traffic environment more selectively. A high approach speed was also a contributory factor to drivers not yielding to the cyclist. When the bicycle crossing was adjacent to the roundabout, a greater proportion of drivers yielded than when the crossing was set back (6 m) from the roundabout. The results suggest that priority regulation at bicycle crossings should vary depending on the location of the crossing at the roundabout.
