PTW crashes

Elvik [ELV 04a] has defined some basic factors which influence the level of risk of road accidents. Among these risk factors some are considered to affect PTWs more specifically, such as low friction (as mentioned above), but also lack of visibihty, road-user rationality, road-user vulnerability and system forgiveness. 

Vehicle technical failures are oidy a minor proportion of PTW road crash contributory factors. On the other hand, for PTWs, road design and road enviromnent factors have a significant influence on the crash severity (e.g. roadside obstacles and barriers, speed reduction installations) even more than on crash occurrence [ACE 06]. However, PTWs are specifically sensitive to inlrastructure design (e.g. ahgnment, curves, intersections, etc.) and maintenance (holes, gravels, vegetation, etc.). Due to this sensitivity, defects on the layout are likely to create more difficulties on PTW riders than on operators of other motorized vehicles. 

It is also noted that a more frequent combination of road crash contributory factors is found in PTW crashes, compared to other road users crashes, which results in the multiplication of the relative risk. For example, it has been foimd that those without a valid license have a higher probability of not wearing a helmet, driving above the speed hmit, driving imder the influence of alcohol and without daytime ranning lights and so on ([PEE 96, REE 96]. 

---

In-depth studies of PTW crashes the MAIDS and Hurt studies... 

The role of human environmental and vehicular factors in PTW crash causation... 

Two groups of riders are at greatest risk of a PTW crash the young and inexperienced riders, and the older riders older in this case being mature 40+ years old riders who are either inexperienced or returning to motorcycling after a long hiatus. 

This research was carried out by a working group of the OECD International Transport Foram, composed of experts from several countries. The chapter starts by presenting the basic trends and figures of PTW mobility, use and safety. Then, a comprehensive review of PTW crash contributory factors is presented (user-, vehicle- or infiastracture-related). Subsequently, the integration of PTW in the Safe Systems approach is discussed, with particular focus on the challenges and particularities involved. Finally, the most promising individual measures for the improvement of PTW mobility and safety are outlined. 

A large majority of PTW crashes are single vehicle crashes occurring on rural roads 25% of all PTW crashes in Italy, 38% in Greece and 44% in Finland and Sweden [2BE 10], Almost one-third of all PTW fatalities occur at junctions - a proportion notably higher compared to other road users (ACEM 2006, [YAN 10]). This stresses the importance of taking specific counter measures for junction safety improvement for PTWs. 

The results are strikingly - and surprisingly - similar, with the principal cause of the crashes in both data sets being the behavior of the driver of the other vehicle, followed by the behavior of the PTW rider. Similar findings were obtained in a British motorcycle causation study where in accidents involving a collision with another vehicle, the motorcycle rider was culpable in less... 

Skilled performance is very critical in crash avoidance while riding PTWs. Hurt et a/.(1981), noted that the median time available to avoid the crash in their 900 crashes was only 1.9 seconds. This is a very short time to detect the impending danger, decide on a proper course of action, and then execute it effectively. According to their crash reconstructions, in 43 percent of the crashes that had enough data, there was a proper evasive action. Yet its execution was correct in only 24 percent of the times that it was attempted. Elliott et ah (2007) also found that control errors and speed violations were significantly associated with the frequency of crashes in which the rider assumed at least some responsibility. 

Speed is generally associated with injury severity, but it also has a consistent effect on the likelihood of a crash. The MAIDS crash investigation teams concluded that in 8 percent of the crashes the motorcycle s speed contributed to the crash, compared to only 5 percent of the crashes in which the other vehicle s speed contributed to the crash. In Spain, Lardelli-Claret et al. (2005) assessed the accident causes of all the PTW injury collisions that occurred in Spain from 1993 to 2002, that did not involve a pedestrian, and in which only one of the drivers or riders was considered culpable. With a total data base of 128,273 crash-involved mopeds and 62,005 crash-involved motorcycles, they calculated the crash risk of the culpable riders relative to that of the non-culpable riders. After adjusting for various confounding variables, they found that the factors that were most over-involved in culpable crashes were inappropriate speed (with an odds ratio of 13 for motorcycles and 10 for mopeds), and excessive speed (with an odds ratio of 7 for motorcycles and 6 for mopeds). The effects of speed in general are discussed in much more details in Chapter 8). 

Because of the inherent instability of PTW, two skills that riders must acquire are acute hazard perception and quick appropriate responses to emerging hazards. Small objects on the road, potholes, pavement deformations, spaces between adjoining pavement segments, cracks in asphalt and concrete, oils spills, loose gravel, and puddles that may be inconsequential to car drivers can be life-threatening hazards to the motorcyclists, and must be avoided at all costs. For example, as part of a motorcycle crash risk study conducted in Australia, Haworth et al. (1997), revisited the same sites where 206 motorcycles crashed and noticed that in 14 percent of the crashes unclean road and loose material on the road probably contributed significantly to... 

For each type of user (car occupants, pedestrians, cyclists and PTW riders), allinjury (whatever the severity), hospitalization and serious-injury (MAIS 3+) rates were estimated. These rates were estimated by dividing the number of injuries by the exposure measurement and scaled per one milhon trips, kilometers or hours. Rates by gender, age group and location ( dense areas and non-dense areas ) were estimated separately for each type of user (except for PTW riders because of insufficient mobility data). Only residents of the Rhone Coimty were included in the study. Crashes and trips were also restricted to the Rhone Coimty. 

With regards to each e q)osure measure, PTW riders had the highest all-injury, hospitalization, and serious-injury rates. In the present study, the amount of excess risk is quantified and is very high. This result is consistent with other studies in France [GAB 05, MER 06, BER 11, LIC 11], the United States [BEC 07] and New Zealand [TIN 10] using police or hospital-based crash data. This high excess of risk is giving much cause for concern. 

There were missing valnes for some residence locations of the casualties and for some crash locations. These missing values were imputed using simple imputation from proportions estimated on observations without missing-values. The rates for PTW riders by gender, age gronp and location separately were not estimated we are concerned abont the reliability of the estimates because of the small number of PTW trips in the RTS. The mobility data provide information only about residents of the... 

Regardless of the countries concerned, however, PTW users are confronted with an excessive risk on the road, which has been qualified as unfair by Elvik [ELV 09], insofar as for the same number of kilometers driven they have a much higher risk of being killed or severely injured than car occupants. They are clearly overrepresented among road traffic casualty figures, even when they are not overrepresented in crash occurrences. 

Other road users should also be made aware of the specific risks associated with PTW vulnerabihty and crash patterns. Conununication campaigns addressing required behavior change should be targeted at key groups of drivers and riders. 

Traffic rules apply equally to operators of two- and four-wheeled vehicles and should be equally enforced. As for other motorized vehicle users, enforcement is needed to improve compliance with key safety mles like speed, drinking and driving, helmet use, proper licenses and a vehicle that meets safety standards. High-visibihty enforcement accompanied by other measures, such as communication and pubhcity has proven to have a strong deterrent effect. Speed enforcement is key to reducing the speed and associated crash risk. Automated speed enforcement has proven its effectiveness for cars, but further adjustments are needed to make it as effective for PTWs. 

It is essential to extend the knowledge on PTW mobility and crash mechanisms... 

However, PTW safety figures have not followed the impressive improvement trends of the last decade that other users safety figures demonstrate. Moreover, per kilometer driven, PTW riders have a much higher risk of being killed than car occupants, between 9 and 30 times higher. PTW riders are also more likely to be very seriously injured in a road crash with long term disabilities than other motorized road users. They are also more vulnerable to impairment by e.g. alcohol. 

Young, inexperienced and male riders are over represented in crashes. The most frequent PTW fatal crashes are single-vehicle crashes, partly due to intrinsic difficulties of riding a PTW (e.g. necessity to keep the balance) and to the higher sensitivity of riders to external perturbations (e.g. wind or poor pavement condition). The other most frequent crash type occurs at intersections with other traffic, involving, for a large number of crashes, a problem of perception and appraisal by the driver and/or the rider. 

---