greater changes to their position and speed on encountering the hazard, but might be more likely to amend their behaviour on the subsequent bend. Methods Ethics Statement Ethical approval for the study was sought on 12th August 2010. The application was reviewed in accordance with the University of Nottingham Faculty of Engineering Ethics Committee protocols and approval was granted on 24th August 2010. All participants gave informed written consent before taking part in the experiment. Participants Sixty two participants were recruited for the study and reimbursed for their time. The participants were all members of the general public and were recruited through local and national adverts, through rider training schools, local motorcycle meetings and the national IAM newsletter. Participants were pre-screened for excessive driving experience so that anyone with a typical annual mileage in excess of 20,000 miles per annum or who held any specialist driving licence (e.g. public service vehicle, light or heavy goods vehicle) was excluded from the study. All participants held at least a provisional UK motorcycle license, had normal or corrected to normal vision and did not suffer from migraines, epilepsy or motion sickness. From the sample, 61 participants completed the study and their data were used for analysis (one participant withdrew with simulator sickness symptoms). Of the participants, 20 were novice riders (having taken or were preparing to take the standard Driving Standards Agency (DSA) motorcycle test within the last 12 months); 21 were experienced riders (who had over 3 years riding experience since passing their motorcycle test, but had no further training) and 20 were advanced riders (who had passed their IAM advanced riding test in the last 3 years). Novice riders were younger than the other 2 groups (mean age = 26.5 years; SD = 8.2 years), while the advanced riders (mean age = 47.4 years; SD = 9.2 years) were slightly older than the experienced riders (mean age = 40.6 years; SD = 9.3 years). Experienced riders and advanced riders were matched for overall riding experience (experienced riders mean experience = 15.6 years; SD = 9.9 years, and advanced riders mean experience = 16.6 years; SD = 11.9 years). There was no significant difference between the 3 groups in terms of the amount of hours spent riding per week (p.0.05). Design Riders rode two laps of a simulated riding scenario, and encountered a set of four left-hand bends and a set of four right- hand bends on each lap. Left-hand bends and right hand bends were analysed independently, but were identical in terms of experimental design. Two sets of analyses were performed on each set of bends. The first set of analyses was concerned with the appearance of a hazard on the third bend of the second lap (which we shall refer to as L2B3: Lap 2, Bend 3). The design adopted for this analysis was a 367 mixed design, with measures from the three rider groups (novice, experienced and advanced) compared across seven sections of the hazard bend. Each section of the bend was 100 ft long (measured along the centre line of the road). The middle 5 sections each comprised a 14.3 degree section of the curve, and the 1st and 7th sections comprised the entry spiral and exit spiral respectively. Spirals are standard terms in geometry for sections of road that connect straight and curved sections. While curves have a constant curvature, spirals linearly increase in Motorcyclist Behaviour on Bends curvature from 0 (when the road is straight) until they join up with the full curve. This provides a gradual transition from straights to curves (and vice versa) and allows the road user to prepare for the full bend. Mean speed, mean lateral position and variance of lateral position were calculated for the seven different sections in order to explore whether these measures changed as riders progressed through the curve and encountered the hazard. Both the left-bend hazard and the right-bend hazard were located between the 5th and 6th sections of the bend, and were visible from section 3. The left bend hazard was a stationary, broken-down car, but the right bend hazard was a moving vehicle, which continued around the curve in the contra-flow lane, driving near the centre line. The second set of analyses required a more complex design. A 2626367 mixed design aimed to compare measures on two bends; one preceding and one following each hazard (bend 2 and bend 4), across both laps (Lap 1 and Lap 2). Any differences between the measures on the second and fourth bends of Lap 2 (L2B2 vs. L2B4) could be due to participants encountering the hazard in the intervening bend (L2B3). However, no hazard occurred between bends 2 and 4 on Lap 1 (L1B2 and L1B4), so these bends provided baseline data to compare against. The other two factors were the three rider groups and the seven curve sections as used in the analysis of the hazard bend. The first bend was excluded from all analyses, since this bend was immediately preceded by a straight road while all other bends were preceded by another bend. Therefore, the road geometry of, and immediately prior to, each analysed bend was identical. Average speed (mph), lateral position (ft) and variance of lateral position (ft2) were calculated for the seven curve sections in order to explore if any effects were isolated to particular parts of the bends (e.g. the apex or the spiral). The reason for this choice of design was to (a) identify if there were any experiential differences in riders’ immediate responses to the hazard, (b) identify if there were any differences in the way rider groups approached bends prior to encountering the hazard, and (c) identify if riders modified their behaviour on bends after experiencing the hazard (i.e. whether there were any differences between pre- and post-hazard bends on Lap 2). A comparison of Lap 2 Bend 2 (L2B2) with Lap 2 Bend 4 (L2B4), and a comparison of L1B4 with L2B4 would reflect any effects of experiencing the hazard. However, any differences between these bends might also include familiarity or practice effects. A comparison of L1B2 with L1B4 provided a baseline estimate of immediate practice within a lap, and a comparison of L1B2 with L2B2 provided an estimate of familiarity and practice from Lap 1 to Lap 2. Therefore, any interactions between bend and lap should help to isolate any effects of experiencing the hazard. Apparatus and Stimuli The main apparatus for the study was the MotorcycleSim simulator which consists of a full size motorcycle (Triumph Daytona 675), two pairs of pneumatic actuators and user input controls. The simulator was used in static mode throughout the study with the pneumatic actuators pressurised to stabilise the motorcycle and rider. The user input controls provided data to the ‘‘STISIM-Drive’’ software, which used this data to provide appropriate visual feedback via a simulated visual environment. The standard motorcycle controls (e.g. throttle, gears, braking input and steering angle) were used to place the rider in the correct location and control their interaction within the scenario. The ‘‘STISIM-Drive’’ software was operated with a tilting horizon and pitching action to support the riding experience of leaning into PLoS ONE | www.plosone.org 3 January 2012 | Volume 7 | Issue 1 | e29978