Measuring the safety effect of raised bicycle crossings using a new research methodology

Before-and-after study methodology was developed and applied to evaluating the effect on bicyclists’ safety of raising urban bicycle crossings by 4 to 12 cm. In total, 44 junctions were reconstructed in this way in Gothenburg, Sweden. Four of these were studied in detail. Before the implementations, bicyclists were riding either in the roadway or on separate paths parallel to the roadway. The paths then ended with short ramps or curb cuts at each cross street, and bicyclists used nonelevated, marked bicycle crossings, similar to pedestrian crosswalks but delineated by white painted rectangles rather than zebra stripes. The results show that the paths with raised crossings attracted more than 50 percent more bicyclists and that the safety per bicyclist was improved by approximately 20 percent due to the increase in bicycle flow, and with an additional 10 to 50 percent due to the improved layout. However, the increased bicyclist volume means that the total number of bicycle accidents is expected to increase. Besides accident analysis, the change in risk was estimated using four different methods: surveys of bicyclists and experts, respectively; conflict data; and a quantitative expert model. Using a Bayesian approach for combining the results shows that the most likely effect of raising the bicycle crossing is a risk reduction of around 30 percent, compared with the before situation with a conventional bicycle crossing. Motorists and pedestrians also saw safety benefits from this traffic-calming measure.