The variance of lateral position was also analysed to assess the extent of any shifts in lane position across the seven sections. There was a significant main effect of rider group (F(2,58) = 3.407; MSe = 0.339; p,0.05), a main effect of curve section (F(6,348) = 38.719; MSe = 1.939; p,0.001), and a significant interaction between rider group and curve section (F(12,348) = 2.536; MSe = 1.939; p,0.01). The interaction is illustrated in Figure 5. The main effect of rider group was due to experienced riders (mean = 1.62 ft2) displaying more lateral movement than the 2 advanced riders (mean = 1.19 ft ), although this was not statisti- cally significant in the Scheffe´ tests (p = 0.069). However, neither the experienced riders nor the advanced riders differed signifi- 2 cantly from the novices (mean = 1.24 ft ). In general, there were significant differences in the amount of lateral movement between each of the seven sections (p,0.05) except between sections 6 and 7 (p = 0.096). Repeated contrasts revealed that the interaction between rider group and section was significant at the beginning of the bend (between sections 1 and 2, p,0.05) and near the hazard (between sections 4 and 5, p,0.05; and between sections 5 and 6, p,0.01). Simple main effects analysis and Scheffe´ tests revealed that during section 1, the experienced riders displayed more lateral movement than both novice (p,0.05) and advanced riders (p,0.01). All 3 groups of riders made an increase in lateral movement between sections 4 and 5 in response to the hazard (p,0.001), but the advanced riders displayed less lateral movement than the experienced riders (p,0.05) and demonstrated a near-significant difference when compared to the novice riders (p = 0.059). This latter finding supports the suggestion that the advanced riders had prepared their lane position for passing the hazard sooner than the other two groups, and therefore needed a significantly smaller correction to their lane position. The novice and experienced riders decreased lateral movement between sections 5 and 6, although this only approached statistical significance for experi- enced riders (for novices p,0.01; for experienced p = 0.053). To summarise, the interaction results arise from the experienced riders making more lateral movement at the beginning of the bend and from novices and experienced riders making more lateral movement in response to the hazard. Responses to the left-hand non-hazard bends A series of 3626267 ANOVAs were conducted on data for speed, lateral position and the variance of lateral position, Motorcyclist Behaviour on Bends comparing the three rider groups across Lap 1 and Lap 2, and across the second and fourth bend (L1B2, L1B4, L2B2 and L2B4), for all seven sections of each curve. It should be noted that the hazard occurred on the 3rd bend of Lap 2 (L2B3), so only L2B4 is considered to be post-hazard, while the other three bends acted as different control conditions to compare against. Analysis of the riders’ mean speed revealed a significant main effect of bend (F(1,58) = 7.633; MSe = 82.095; p,0.01), a signif- icant main effect of lap (F(1,58) = 8.589; MSe = 147.813; p,0.01), and an interaction between the two (F(1,58) = 15.177; MSe = 72.914; p,0.001). Simple main effects showed that on bend 2, riders were significantly faster during Lap 2 than they were on Lap 1(L2B2.L1B2; F(1,60) = 26.741; MSe = 12.756; p,0.001). We suggest that this represents a familiarity effect, with riders feeling more comfortable with higher speeds having already navigated the bend once before. However, there was no significant difference between Lap 1 and Lap 2 for bend 4 (p = 0.850). The familiarity effect was possibly overridden by the appearance of the hazard on L2B3. Furthermore, riders increased their speed between L1B2 and L1B4 (F(1,60) = 20.834; MSe = 11.468; p,0.001), but did not display this increase in speed on Lap 2 (p = 0.512). Instead of an increase, riders decreased their speed slightly on Lap 2 Bend 4. Again, this suggests that, on the first Lap, riders became more comfortable with the repetitive bends as they navigated through them, resulting in higher speeds for bend 4 than bend 2. However, as with the effect of Lap, this did not translate to the post hazard bend (L2B4) which suggests that speed had either reached a ceiling point, or that encountering the hazard on L2B3 negated any further speed increases on L2B4. These findings are illustrated in Figure 6. A significant main effect was also observed for road section on mean speed (F(6,348) = 7.464; MSe = 14.431; p,0.001) and an interaction between bend and section (F(6,348) = 3.773; MSe = 9.324; p,0.01), shown in Figure 7. Simple main effects analysis revealed that there was an effect of section on bend 2 (F(6,360) = 13.824; MSe = 4.759; p,0.001), but not on bend 4 (p,0.05). Repeated contrasts showed that on bend 2, there was a significant increase in speed through all adjacent sections from 2 to 6 (all p,0.05) with the greatest increase between sections 4 and 5 (p,0.001). Also, there was a significant decrease in speed between sections 6 and 7 (p,0.05). The differences between bend 2 and bend 4 were only significant for the first 3 sections (p,0.01). On subsequent sections, average speed on bend 2 resembled average speed on bend 4. Figure 5. Variance of lateral position across the seven bend sections for the rider groups (with standard error bars added). doi:10.1371/journal.pone.0029978.g005 Figure 6. Average speed of riders on the 2nd and 4th left-hand bends across the two laps (with standard error bars added). doi:10.1371/journal.pone.0029978.g006 PLoS ONE | www.plosone.org 7 January 2012 | Volume 7 | Issue 1 | e29978