Figure 9. Average lateral position of the rider groups over the seven bend sections for bend 2 (upper panel) and bend 4 (lower panel). doi:10.1371/journal.pone.0029978.g009 road section on L2B3 were primarily driven by the appearance of the hazard. Responses to the right-hand hazard bend A series of 367 ANOVAs were conducted on data for speed, lateral position, and the variance of lateral position comparing the measures of each rider group across the 7 sections of the curve. Analysis of average speed revealed a significant main effect of curve section (F(6,348) = 6.567; MSe = 18.004; p,0.001). Repeat- ed contrasts showed that riders significantly decreased their speed between sections 3 and 4 when the hazard first became visible (p,0.01), then significantly increased their speed between sections 6 and 7 (p,0.05) after the hazard (Figure 11). There was no effect for rider group and no interaction between rider group and curve section. The same analysis was conducted on mean lateral position. It should be noted however that the measures have different ramifications when considering right-hand bends rather than left-hand bends. With the left-hand bends a move away from the centre line towards the edge of the road is considered to potentially increase progression (if timed correctly) but may decrease visibility Motorcyclist Behaviour on Bends around the bend. With the right-hand bends however, a move towards the centre line, or even over the centre line into the contra-flow lane, will increase progression. Such rightward movement will also decrease visibility around the bend but to a lesser extent than a leftward movement in a left-hand bend. Analysis of the lateral position of the riders revealed a significant main effect of rider group (F(2,58) = 4.140; MSe = 2.53; p,0.05) with experienced riders (mean = 24.25 ft) travelling significantly closer to the centre line than advanced riders (mean = 25.55 ft; p,0.05). The difference between experienced riders and the novice riders (mean = 25.41 ft) was not statistically significant (p = 0.075) despite the novice road position being closer to that of the advanced riders. A significant main effect was also observed for curve section (F(6,348) = 22.487; MSe = 4.747; p,0.001) and an interaction between rider group 6 curve section was identified (F(12,348) = 3.610; MSe = 4.747; p,0.001). Repeated interaction contrasts revealed that this interaction was only significant between sections 6 and 7 (p,0.05). At section 6, all rider groups were a comparable distance from the centre line (25.4 ft, 25.2 ft, and 24.8 ft for novice, experienced and advanced riders respectively). In section 7 (the exit spiral) all groups had moved toward the centre line, although the novice and experienced riders made less of a shift than the advanced riders (23.8 ft, 23.3 ft, and 21.6 ft, respectively). This was supported by simple main effects analysis comparing the three rider groups at each level of road section. Simple main effects analysis of each rider group across the 7 sections (with repeated contrasts across sections) showed that all three rider groups made significant changes in lateral position over the first three curve sections, moving towards the centre line (p,0.01), but did not change their lateral position between sections 3 and 4 as they approached the apex of the bend. Between sections 4 and 5, only novice and experienced riders made a significant change in lateral position away from the centre line in response to the hazard (p,0.001). Between sections 5 and 6, only novice and advanced riders made a significant change in lateral position, moving back towards the centre line (p,0.05 for novices; p,0.001 for advanced riders). Then between sections 6 and 7, all three rider groups made significant changes in lateral position back towards the centre line (p,0.001). Simple main effects analysis also showed that in section 1, the effect of rider group only approached significance (p = 0.067), with experienced riders riding closer to the centre line than advanced riders while novices were positioned in-between. In sections 2, 3 and 4, the difference between advanced and experienced riders reached significance (maximum p,0.05). However, in section 3 the experienced riders were also significantly closer to the centre line than the novice riders (p,0.05). In sections 5 and 6, there were no significant differences in the lateral positions of the 3 groups. In section 7, the advanced riders rode significantly closer to the centre line than both the novice riders (p,0.01) and the experienced riders (p,0.05), supporting the repeating interaction contrasts in identifying the source of the rider group 6 road section interaction. These results are illustrated in Figure 12. To summarise, the advanced riders remained further out from the centre line than other riders until they had better visibility through the bend and they had successfully negotiated the hazard. Their safer positioning required less adjustment when the hazard was encountered. In contrast, the experienced riders and, to a much lesser extent, the novice riders shifted their position nearer to the centre line at an earlier point in the bend. When the hazard was encountered, this resulted in a sudden leftward shift away from the centre line. PLoS ONE | www.plosone.org 9 January 2012 | Volume 7 | Issue 1 | e29978