Motorcyclist Behaviour on Bends Figure 2. Rider view of vehicle hazard on the left-hand bend (left panel) and on the right-hand bend (right panel). doi:10.1371/journal.pone.0029978.g002 although traffic did appear in other sections of the main riding scenario. Procedure Participants conducted two practice sessions on MotorcycleSim to familiarise them with the simulator controls (e.g. steering, throttle response, gears, and braking inputs), an emergency stop (to assess the braking potential of the simulator) and overtaking manoeuvres around the slow moving vehicles. The two practice sessions lasted between 8 to 10 minutes in total. Throughout the experiment, participants wore a helmet whilst on the simulator so that their field of view would be similar to that experienced on a real motorcycle. Participants then completed the main riding scenario. They were instructed that the route would take 20 to 25 minutes to complete and that it would repeat itself half way through. Participants were also instructed to ride as they would in the real world. If participants left the main carriageway (by more than 1 ft on either side of the road) an accident was registered, the scenario paused and they were placed back on the road to continue the simulated route from that point. An allowance of 1 ft meant that riders could pull over to the road side if necessary without it being recorded as an accident. Measures of simulator sickness symptoms were recorded in between the practice and testing sessions. Finally, participants were fully debriefed on the purpose of the study and paid for their time. Results The results for the left-hand S-bends are reported first, followed by the results of the right-hand bends. Each series of bends was analysed in two ways. First participants’ immediate responses to the hazard on L2B3 were analysed. Mean speed, mean lateral position and variance of lateral position were calculated for the seven curve sections in order to explore whether these measures changed as riders progressed through the curve and encountered the hazard (which was positioned between the 5th and 6th sections, and visible from the 3rd section onwards). The second analysis compared the non-hazard bends across the factors of Lap and Bend number (L1B2, L1B4, L2B2 and L2B4). This analysis revealed any differences in how the riders generally approached the bends, and whether they changed their behaviour following their encounter with the hazard. All interactions were explored with repeated interaction contrasts and analysis of simple main effects. Within group main effects were explored with repeated contrasts, while post-hoc between group main effects were analysed using Scheffe´ tests. Responses to the left-hand hazard bend (L2B3) A series of 367 ANOVAs were conducted on data for speed, lateral position, and the variance of lateral position comparing the measures for each group across the seven sections of the curve. Analysis of average speed revealed a significant effect of curve section (F(6,348) = 59.603; MSe = 27.411; p,0.001). Repeated contrasts indicated that riders significantly increased their speed from an average of 49.0 mph to 49.8 mph between sections 2 and 3 then significantly decreased their speed to an average of 47.2 mph on section 4. This corresponds with the hazard becoming visible in section 3. Riders dropped their speed more dramatically to 38.2 mph on section 5 then continued at a similar speed before significantly increasing their speed to an average of 41.0 mph on section 7 (all at p,0.05). These findings are illustrated in Figure 3. There was no group effect. Mean lateral position of the motorcycle produced a measure between 212 ft and +12 ft where zero was the centre line of the road and increasingly negative numbers reflect positions further to the left of the lane, with a score of 212 reflecting the left edge of the road. Any positive score of mean lateral position reflects an incursion into the contra-flow lane. A significant main effect was observed for rider group upon lane position (F(2,58) = 8.802; MSe = 1.813; p,0.001). Scheffe´ tests revealed that advanced riders rode significantly closer to the centre line (mean = 23.9 ft) than both experienced (mean = 25.093 ft; p,0.05) and novice riders (mean = 25.604 ft; p,0.01). However, experienced and novice riders did not differ significantly (p = 0.482). A main effect of curve section was also observed (F(6,348) = 86.002; MSe = 3.647; p,0.001) as well as an interaction between rider group and curve section (F(12,348) = 6.271; MSe = 3.647; p,0.001). Repeated contrasts revealed that this interaction was significant only between sections 4 and 5 (p,0.05) and between sections 5 and 6 (p,0.01). Through sections 1 to 4, despite all riders moving across to the left edge of the road, the advanced riders stayed significantly closer to the centre line than both the novice and experienced riders (p,0.01, as indicated by simple PLoS ONE | www.plosone.org 5 January 2012 | Volume 7 | Issue 1 | e29978