road users in a safe environment whilst still retaining an acceptable level of ecological validity [14]. Furthermore, simulations offer a means of manipulating the environment in a controlled way that is not possible in the real world. Thus it is possible to assess how different road users with varying levels of skill and training cope with the same situation. For instance, Crundall, Andrews, van Loon and Chapman [15] compared trained and untrained car drivers on their approach to a series of highly controlled virtual hazards, and noted the positive impact of training on speed and braking signatures on the approach to the hazards (see also [16,17]). Driving simulators have also been used to assess the behavioural effectiveness of road engineering factors upon speed choice of drivers when negotiating bends. Drivers approaching bends demonstrated improved speed adaptation if the curve radius was highlighted, either implicitly (e.g. with hazard marker posts or chevrons) or explicitly (e.g. with an advisory speed sign or flashing warning) [18]. While such highly controlled yet ecologically valid studies are still limited within the car driving domain, as far as the authors are aware they are non-existent in the motorcycle literature. There is a limited amount of research on motorcycle simulators which has focussed upon detection and avoidance of hazards, though levels of control and manipulation have not reached those of comparable studies with car simulators [19–22]. Rationale The current study used a new motorcycle simulator (Motorcy- cleSim) to investigate rider behaviour in bends. MotorcycleSim was developed at the University of Nottingham and uses a full motorcycle interface linked to a large screen presentation of specially-modified ‘‘STISIM-Drive’’ software [23]. Thus the simulator retains the functional fidelity of a real motorcycle whilst providing complete control over the development of road geometry, and the ability to record a wide variety of measures at a high sample rate. Given that accidents on bends are linked with inexperience, the aim of the study was to compare riders of varying skill and experience in order to assess the problems associated with navigating a series of left and right bends, and identify the potential strategies that the safer riders might adopt. For instance one might expect that experienced or advanced riders crash less frequently on bends as a result of better road positioning as well as a more appropriate choice of speed. The following experiments were therefore designed to compare novice, experienced and advanced riders in order to investigate if experience and advanced training offer accumulative, or different, benefits when negotiating bends, especially when faced with an unexpected hazard hidden around a bend, such as a broken-down vehicle. Advanced riders were defined as riders who had passed an advanced motorcycle test following training provided by the Institute of Advanced Motorists (IAM) in the last 3 years. This advanced training course focuses on a system of motorcycle control as a way of approaching and negotiating potential hazards in a methodical, safe manner and encompasses five factors of safe riding: Information, Position, Speed, Gear and Acceleration or the ‘IPSGA’ system of motorcycle control [24]. There are two key influences on how a rider might approach a bend. The first is progression: In order to make the fastest progression through a bend, a rider might adopt what is known as the ‘racing line’, moving from the outside edge of a curve to the inside edge as they approach the apex. After passing the apex the rider then moves back out towards the outside edge when exiting the curve. The intention of this manoeuvre is to minimise the travel time through the curve by optimising the distance travelled Motorcyclist Behaviour on Bends with the speed that can be successfully maintained. The other influence is safety: In the UK, when negotiating a left hand bend, a rider might adopt a position closer to the centre line in order to gain the best visibility throughout the bend. Conversely, on a right hand bend, a rider might adopt a position closer to the left-hand side of the road to optimize visibility throughout the bend. Since two key aspects of training are safety and progression, we might expect advanced riders to only take the racing line after they have obtained a sufficient view of what is around the bend. The DSA recognise the importance of positioning in bends, and this is included in the road test. Novice riders preparing for the DSA test are formally taught to change their position to the left to increase visibility on a right hand bend, and to maintain a dominant (centre of lane) position on a left hand bend, balancing visibility with the need to avoid oncoming traffic which is close to the centre line. Furthermore, novices are taught to consider the physics of the motorcycle when navigating a bend: Given that riders typically lean towards oncoming traffic on a right-hand bend, and towards road furniture on a left-hand bend, taking a severe progressive line could mean that there is more danger of the rider coming into contact with other objects, even if the wheels of the motorcycle are within the correct lane. However, despite their recent training, novices are more likely to be involved in accidents on bends, so we might expect this group to choose sub-optimal positioning and speeds around bends compared to the experienced and advanced riders. For instance, over-confidence might lead them to take a more pronounced racing line which eschews safety concerns. Alternatively, it is plausible that they try to optimise visibility but still under-estimate speed. In the following experiments, we recorded speed and lane position of riders navigating two sets of left and right bends on two laps of a virtual riding scenario. In all bends the ground at each side of the carriageway was banked and populated with trees to prevent riders from seeing beyond the apex of the curve. This control allowed for both the ‘racing line’ and the ‘visibility line’ to be equally plausible riding options. In addition to monitoring riding style on empty bends, riders encountered two hazards on the second lap. The first hazard was positioned on the penultimate left bend and the second hazard was positioned on the penultimate right bend. This provided an opportunity to assess whether the behaviour that was adopted in the earlier curves had an impact on the extent of the avoidance behaviour that was required upon meeting the hazard. The left- bend hazard was a broken-down car on the left-hand verge, hidden around the apex of the curve. The right-bend hazard was an oncoming vehicle in the contra-flow lane, driving near the centre line of the road. Both hazards were designed to cause problems for riders who favoured a severe racing line at the expense of visibility. Finally, measures taken from the navigation of the final left and right bends (post-hazard) provided an opportunity to assess whether the riders immediately changed their approach to the curve as a result of encountering the hazard on the previous bend. It was predicted that advanced riders would adopt a speed and lane position that was commensurate with the dangers posed by a blind bend (i.e. slower and more towards the centre line in the left- hand bends, or more towards the left in the right-hand bends), and as such should require less modification to their riding style when the hazard was spotted. It was predicted that there would be more similarities between the experienced riders and the advanced riders in terms of riding style, than between the novices and advanced riders. We believed the novices were most likely to favour progression over safety adopting an early racing line and inappropriate speed. Thus novices should be required to make PLoS ONE | www.plosone.org 2 January 2012 | Volume 7 | Issue 1 | e29978