Risks on the roads In a recent article about global trends in injury, 1 Sally Murray describes preven- tion efforts for traffic-related injuries, but 2 independent trends in the devel- oped world may reverse some of the im- provements that have already been made: the aging of the population and the increase in the use of sport utility ve- hicles (SUVs). 2,3 Despite improvements to newer passenger vehicles to reduce the effect of collisions with larger vehi- cles, including SUVs, concern persists regarding the greater risk of injury to the drivers and occupants of passenger vehi- cles and to pedestrians during collisions between vehicles of differing size and mass 4,5 (these factors being the chief de- terminants in severity of injuries). In the United States, 40% of new ve- hicles purchased are classified as light trucks or vans, many of which are SUVs. The preference for an SUV is shaped not only by individual choice but also by environmental influences, including economic and social factors. 6 SUVs, some of which are marketed and purchased for their perceived safety im- age, are suggested to offer robust pro- tection for child occupants. However, a recent study showed that despite greater vehicle weight, aggressive vehi- cle design and size of SUVs, the safety benefits for child occupants are similar to those offered by small vehicles. 7 Given that motor vehicle crashes re- main the leading cause of death and ac- quired disability in children, 8 these data are troubling at best. SUVs also have the highest death rate for their own oc- cupants of any broad class of vehicles, mainly because of high rollover rates. Traffic safety literature indicates that SUVs and trucks inflict substantial ex- ternal safety costs when involved in a collision, causing damage to other vehi- cles, road infrastructure, roadside ob- jects and vulnerable road users. 3,6,7,9 In particular, the risk of injury is an impor- tant deterrent to walking and cycling. In the United Kingdom, cycling accounted for nearly 25% of all road traffic in 1951, but by 1994 this figure had fallen to just 1%. 10 The number of miles walked also declined, on average, by 17% between 1975/76 and 1994. 10 In a recent study that explored why children don’t walk to school more often, 40% of parents reported traffic danger as one of several factors. 11 If traffic danger continues to discourage people of all ages from walking and cycling, the disease burden related to inactivity will increase. Ediriweera Desapriya Department of Pediatrics Centre for Community Child Health Research Vancouver, BC Ian Pike Director Pamela Joshi Research Assistant BC Injury Research and Prevention Unit Vancouver, BC REFERENCES 1. Murray S. Global injury and violence. CMAJ 2006;174(5):620-1. 2. Simms C, O’Neill D. Sports utility vehicles and older pedestrians: a damaging collision. Inj Prev 2006;12:6-7. 3. Desapriya EB, Chipman M, Joshi P, et al. The risk of injury and vehicle damage in vehicle mis- matched crashes. Int J Inj Contr Saf Promot 2005; 12:191-2. 4. World report on road traffic injury prevention 2004. Geneva: World Health Organization; 2004. 5. Desapriya EB, Pike I, Kinney J. The risk of injury and vehicle damage severity in vehicle mismatched side impact crashes in British Columbia. Int Assoc Traffic Saf Sci Res 2005;29:60-6. 6. Acierno S, Kaufman R, Rivara FP, et al. Vehicle mismatch: injury patterns and severity. Accid Anal Prev 2004;36:761-72. 7. Daly L, Kallan MJ, Arbogast B, et al. Risk of injury to child passengers in sport utility vehicles. Pedi- atrics 2006;117:9-14. 8. Soubhi H, Raina P, Kohen D. Neighborhood, fam- ily, and child predictors of childhood injury in Canada. Am J Health Behav 2004;28(5):397-409. 9. Crandall JR, Bhalla KS, Madeley NJ. Designing road vehicles for pedestrian protection. BMJ 2002; 324:1145-8. 10. Road transport and health. London (UK): British Medical Association; 1997. 11. Centers for Disease Control and Prevention. Barri- ers to children walking and biking to school — United States, 1999. MMWR Morb Mortal Wkly Rep 2002;51(32):701-4. DOI:10.1503/cmaj.1060073 Sally Murray’s article on rates of global injury and violence 1 highlights the role of traffic-related injury and death. In discussions of traffic injuries, there is a tendency to use SUVs as scapegoats for increased risk to other road users and pedestrians because of incompatibili- ties between SUVs and other vehicles in terms of height, weight and frame geometry. This heightened risk is well known and is of even greater magni- tude for full-sized trucks and vans. 2,3 However, a rapid evolution is under way in the design of SUVs, from obso- lete body-on-frame construction to uni- body designs, resulting in benefits to occupants in handling and ride quality. It is likely that these new designs also decrease the risk to other road users, although perhaps unintentionally. Until the recent arrival of the Honda Ridgeline, no light trucks have used uni- body technology. All other vehicles in the light-truck category retain conven- tional body-on-frame designs, which align stiff longitudinal steel members with the head and upper torso of car oc- cupants. This design, in combination with non-independent rear suspension, a recent trend to increasing frame height and the attraction that light trucks hold for aggressive young male drivers, ren- ders these vehicles lethal. Currently, collision data are assem- bled by lumping data for disparate frame designs into categories that de- scribe external appearance better than internal construction. Much research remains to be done before the effect of frame construction can be quantified. 4 Wider recognition of the relative risks posed by specific vehicles and frame types to other vehicles, cyclists Letters CMAJ • June 6, 2006 • 174(12) | 1743 © 2006 CMA Media Inc. or its licensors