Motorcyclist Behaviour on Bends Figure 7. Average speed over 7 bend sections for bend 2 and bend 4 (with standard error bars). doi:10.1371/journal.pone.0029978.g007 In relation to mean lateral position a significant main effect was observed for rider group (F(2,58) = 23.981; MSe = 0.998; p,0.001), illustrating that advanced riders (mean = 25.399 ft) rode closer to the centre line than both novice (mean = 27.331 ft; p,0.001) and experienced riders (mean = 27.241 ft; p,0.001) during the non-hazard left bends. A significant effect was also observed for lap (F(1,58) = 5.534; MSe = 7.886; p,0.05), with riders generally riding closer to the middle of the road on Lap 2 (mean = 26.497 ft) compared to Lap 1 (mean = 26.817 ft). However, these main effects were subsumed by a significant lap 6 rider group interaction (F(2,58) = 4.424; MSe = 7.886; p,0.05), which revealed that the move towards the centre line noted in Lap 2 was only significant for novices (F(1,19) = 11.829; MSe = 0.500; p,0.01). An interaction between rider group 6 lap 6 bend also approached significance (F(2,58) = 2.745; MSe = 7.823; p = 0.07). Simple main effects analysis revealed that the advanced riders rode significantly closer to the centre than the novice and experienced riders on both bends on both laps (maximum p,0.05). Novice riders rode closer to the centre of the road on L2B4 compared to L1B4 (F(1,19) = 8.123; MSe = 1.256; p,0.05). There were no effects of lap or bend for experienced riders (p,0.05). However, on Lap 1 the advanced riders rode the fourth bend (L1B4) closer to the centre than the second bend (L1B2; F(1,19) = 4.789; MSe = 1.161; p,0.05), and also rode the second bend closer to the centre on Lap 2 (L2B2) than on Lap 1 (L1B2; F(1,19) = 9.214; MSe = 0.941; p,0.01). These findings are illustrated in Figure 8. There are two interesting points to take from this result: First, the novices appear to move more towards the centre of the road after seeing the hazard. Secondly, advanced riders appeared to use their position on Lap 1 Bend 2, as a gauge for how they approached subsequent bends. After Lap 1 Bend 2 they moved closer to the centre line on all other bends, perhaps reflecting dissatisfaction with their position on this initial bend. The experienced riders do not change their position at all. The analysis of lateral position also revealed a significant main effect of curve section (F(6,348) = 146.203; MSe = 4.520; p,0.001), an interaction between rider group 6 curve section (F(12,348) = 5.024; MSe = 4.520; p,0.001) and an interaction between rider group 6 curve section 6 bend (F(12,348) = 1.926; MSe = 2.075; p,0.05). Figure 8. Average lateral position of rider groups for bends 2 and 4, over Lap 1 and 2. doi:10.1371/journal.pone.0029978.g008 As shown in Figure 9, on Bend 2 novices moved towards the left-hand edge of the road between sections 1 and 4 (all p,0.05). On bend 4, the novice riders still moved over to the left at the start of the bend, but only the differences between the first three sections were significant (p,0.001). The experienced riders showed a similar pattern, moving over to the left at the start of the bends. However, differences were significant between adjacent sections from 1 to 3 for bend 2 (p,0.001) and from 1 to 4 for bend 4 (maximum p,0.05). In contrast, the advanced riders continued to move to the left after the apex of the bend, significantly changing their lateral position between all adjacent sections (maximum p,0.05), apart from sections 3 to 4 in bend 2 and between sections 3 and 5 in bend 4. Despite this, advanced riders rode significantly closer to the centre line of the bend than the experienced and novice riders during sections 1 to 5 on bend 2 (p,0.01) and during sections 1 to 6 on bend 4 (p,0.001, apart from advanced vs. experienced in section 1 where p,0.05). If the adoption of a ‘racing line’ is indicated by a move from the centre line across to the left-hand side of the road at some point during a left-hand curve, then it is clear from Figure 9 that experienced and novice riders adopted a more pronounced racing line than advanced riders, and that they initiated the racing line earlier in the bend. The rapid shift in positioning suggests they adopted a racing line before they could see around the blind bend. The advanced riders however adopted a less severe racing line, involving a smaller shift to the left that was spread over a longer distance and time frame. This was exaggerated even further in bend 4 and suggests that advanced riders were aware of the need for visibility over and above the desire for the racing line. The final analysis of the non-hazard left bends compared the variance of lateral position across rider group, bend, lap, and road section (3626267). There was a significant main effect of curve section (F(6,348) = 7.825; MSe = 2.443; p,0.001). Repeated contrasts revealed significant decreases in variance of lateral position between sections 1 and 2, and between sections 2 and 3, and a significant increase in variance of lateral position between sections 5 and 6 (p,0.001). These findings are illustrated in Figure 10. Unlike the analysis of the left-hand hazard bend (L2B3) there were no main effects or interactions involving rider group. This suggests that any group differences in lateral variance across PLoS ONE | www.plosone.org 8 January 2012 | Volume 7 | Issue 1 | e29978