Kavi S. Bhalla

Designing road vehicles for pedestrian protection

Collisions between pedestrians and road vehicles present a major challenge for public health, trauma medicine, and traffic safety professionals. More than a third of the 1.2 million people killed and the 10 million injured annually in road traffic crashes worldwide are pedestrians.1 Compared with injured vehicle occupants, pedestrians sustain more multisystem injuries, with concomitantly higher injury severity scores and mortality.2 Although a disproportionately large number of these crashes occur in developing and transitional countries, pedestrian casualties also represent a huge societal cost in industrialised nations. In Britain pedestrian injuries are more than twice as likely to be fatal as injuries to vehicle occupants3 and result in an average cost to society of £57 400, nearly twice that of injuries to vehicle occupants.4 #### Summary points Pedestrian-vehicle crashes are responsible for more than a third of all traffic related fatalities and injuries worldwide Lower limb trauma is the commonest pedestrian injury, while head injury is responsible for most pedestrian fatalities Standardised tests that simulate the most common pedestrian-vehicle crashes are being used to evaluate vehicle countermeasures to reduce pedestrian injury Energy absorbing components such as compliant bumpers, dynamically raised bonnets, and windscreen airbags are being developed for improved pedestrian protection Despite the size of the pedestrian injury problem, research to reduce traffic related injuries has concentrated almost exclusively on increasing the survival rates for vehicle occupants. Most attempts made to reduce pedestrian injuries have focused solely on isolation techniques such as pedestrian bridges, public education, and traffic regulations and have not included changes to vehicle design. The lack of effort devoted to vehicle modifications for pedestrian safety has stemmed primarily from a societal view that the injury caused by a large, rigid vehicle hitting a small, fragile pedestrian cannot be significantly reduced by alterations to the vehicle structure. Crash engineers, …

Building national estimates of the burden of road traffic injuries in developing countries from all available data sources: Iran.

Objective: To use a range of existing information sources to develop a national snapshot of the burden of road traffic injuries in one developing country—Iran. Methods: The distribution of deaths was estimated by using data from the national death registration system, hospital admissions and outpatient visits from a time-limited hospital registry in 12 of 30 provinces, and injuries that received no institutional care using the 2000 demographic and health survey. Results were extrapolated to national annual incidence of health burden differentiated by age, sex, external cause, nature of injuries and institutional care. Results: In 2005, 30 721 Iranians died annually in road traffic crashes and over one million were injured. The death rate (44 per 100 000) is the highest of any country in the world for which reliable estimates are available. Road traffic injuries are the third leading cause of death in Iran. While young adults are at high risk in non-fatal crashes, the elderly have the highest total death rates, largely due to pedestrian crashes. While car occupants lead the death count, motorised two-wheeler riders dominate hospital admissions, outpatient visits and health burden. Conclusions: Reliable estimates of the burden of road traffic injuries are an essential input for rational priority setting. Most low income countries are unlikely to have national injury surveillance systems for several decades. Thus national estimates of the burden of injuries should be built by collating information from all existing information sources by appropriately correcting for source specific shortcomings.

Fire-related deaths in India in 2001: a retrospective analysis of data

BACKGROUND Hospital-based studies have suggested that fire-related deaths might be a neglected public-health issue in India. However, no national estimates of these deaths exist and the only numbers reported in published literature come from the Indian police. We combined multiple health datasets to assess the extent of the problem. METHODS We computed age-sex-specific fire-related mortality fractions nationally using a death registration system based on medically certified causes of death in urban areas and a verbal autopsy based sample survey for rural populations. We combined these data with all-cause mortality estimates based on the sample registration system and the population census. We adjusted for ill-defined injury categories that might contain misclassified fire-related deaths, and estimated the proportion of suicides due to self-immolation when deaths were reported by external causes. FINDINGS We estimated over 163 000 fire-related deaths in 2001 in India, which is about 2% of all deaths. This number was six times that reported by police. About 106 000 of these deaths occurred in women, mostly between 15 and 34 years of age. This age-sex pattern was consistent across multiple local studies, and the average ratio of fire-related deaths of young women to young men was 3:1. INTERPRETATION The high frequency of fire-related deaths in young women suggests that these deaths share common causes, including kitchen accidents, self-immolation, and different forms of domestic violence. Identification of populations at risk and description of structural determinants from existing data sources are urgently needed so that interventions can be rapidly implemented.

Data Sources for Improving Estimates of the Global Burden of Injuries: Call for Contributors

Kavi Bhalla and colleagues invite individuals and organizations to provide local injury data sources to help inform estimates of the global burden of injuries.

Experiments for Establishing Pedestrian-Impact Lower Limb Injury Criteria

This paper discusses lower limb injury impacts to pedestrians. Previous lateral knee bending and shear tests have reported knee joint failure moments close to failure bending moments for the tibia and femur. Eight tibias, eight femurs and three knee joints were tested in lateral bending and two knee joints were tested in lateral shear. Seven previous studies on femur bending, five previous studies on tibia bending, two previous studies on knee joint bending, and one on shear were reviewed and compared with the current tests. All knee joint failures in the current study were either epiphysis fractures of the femur or soft tissue failures. The current study reports an average lateral failure bending moment for the knee joint (134 Nm SD 7) that is dramatically lower than that reported in the literature (284-351 Nm), that reported in the current study for the tibia (291 Nm SD 69) and for femur (382 Nm SD 103). While this research has demonstrated the importance of realistic boundary conditions, more research is necessary to determine a statistically valid impact threshold for the knee joint.

Influence of vehicle body type on pedestrian injury distribution

Pedestrian impact protection has been a growing area of research over the past twenty or more years. The results from many studies have shown the importance of providing protection to vulnerable road users as a means of reducing roadway fatalities. Most of this research has focused on the vehicle fleet as a whole in datasets that are dominated by passenger cars (cars). Historically, the influence of vehicle body type on injury distribution patterns for pedestrians has not been a primary research focus. In this study we used the Pedestrian Crash Data Study (PCDS) database of detailed pedestrian crash investigations to identify how injury patterns differ for pedestrians struck by light trucks, vans, and sport utility vehicles (LTVs) from those struck by cars. AIS 2+ and 3+ injuries for each segment of vehicles were mapped back to both the body region of the pedestrian injured and the vehicle source linked to that injury in the PCDS database. The findings indicate that the head is the most frequently injured body region for both vehicle segments, but the lower extremity is second for cars, whereas the torso is second for LTVs. Mapping the injuries back to the vehicles we find that the most frequent sources of injury for cars are the windshield and bumper, while for the LTVs it is the hood and hood leading edge.

Injury tolerance and moment response of the knee joint to combined valgus bending and shear loading.

Valgus bending and shearing of the knee have been identified as primary mechanisms of injuries in a lateral loading environment applicable to pedestrian-car collisions. Previous studies have reported on the structural response of the knee joint to pure valgus bending and lateral shearing, as well as the estimated injury thresholds for the knee bending angle and shear displacement based on experimental tests. However, epidemiological studies indicate that most knee injuries are due to the combined effects of bending and shear loading. Therefore, characterization of knee stiffness for combined loading and the associated injury tolerances is necessary for developing vehicle countermeasures to mitigate pedestrian injuries. Isolated knee joint specimens (n=40) from postmortem human subjects were tested in valgus bending at a loading rate representative of a pedestrian-car impact. The effect of lateral shear force combined with the bending moment on the stiffness response and the injury tolerances of the knee was concurrently evaluated. In addition to the knee moment-angle response, the bending angle and shear displacement corresponding to the first instance of primary ligament failure were determined in each test. The failure displacements were subsequently used to estimate an injury threshold function based on a simplified analytical model of the knee. The validity of the determined injury threshold function was subsequently verified using a finite element model. Post-test necropsy of the knees indicated medial collateral ligament injury consistent with the clinical injuries observed in pedestrian victims. The moment-angle response in valgus bending was determined at quasistatic and dynamic loading rates and compared to previously published test data. The peak bending moment values scaled to an average adult male showed no significant change with variation in the superimposed shear load. An injury threshold function for the knee in terms of bending angle and shear displacement was determined by performing regression analysis on the experimental data. The threshold values of the bending angle (16.2 deg) and shear displacement (25.2 mm) estimated from the injury threshold function were in agreement with previously published knee injury threshold data. The continuous knee injury function expressed in terms of bending angle and shear displacement enabled injury prediction for combined loading conditions such as those observed in pedestrian-car collisions.

Methods for developing country level estimates of the incidence of deaths and non-fatal injuries from road traffic crashes

The estimates of the incidence of deaths and non-fatal injuries from road traffic crashes are essential inputs for prioritising national health and transport policies. This article sketches a methodology for assembling such estimates at the country level by piecing together data from a wide array of sources that include death registers, hospital records, funeral records, health surveys and police reports. Using examples of the types of data sources available in four developing countries (Iran, Mexico, Ghana and India), methods are proposed for making these consistent and extrapolating to estimates of injury incidence at the country level. This requires filling information gaps, mapping from varying case definitions, deriving population-based incidence estimates from sources that may not track denominator populations, and appropriately reapportioning cases assigned to poorly specified causes. The principles proposed here will form the methodological basis for a series of country reports to be published in the future.

Estimating the distribution of external causes in hospital data from injury diagnosis

Hospital discharge datasets are a key source for estimating the incidence of non-fatal injuries. While hospital records usually document injury diagnosis (e.g. traumatic brain injury, femur fracture, etc.) accurately, they often contain poor quality information on external causes (e.g. road traffic crashes, falls, fires, etc.), if such data is recorded at all. However, estimating incidence by external causes is essential for designing effective prevention strategies. Thus, we developed a method for estimating the number of hospital admissions due to each external cause based on injury diagnosis. We start with a prior probability distribution of external causes for each case (based on victim age and sex) and use Bayesian inference to update the probabilities based on the victims injury diagnoses. We validate the method on a trial dataset in which both external causes and injury diagnoses are known and demonstrate application to two problems: redistribution of cases classified to ill-defined external causes in one hospital data system; and, estimation of external causes in another hospital data system that only records nature of injuries. In comparison with age-sex proportional distribution (the method usually employed), we found the Bayesian method to be a significant improvement for generating estimates of incidence for many external causes (e.g. fires, drownings, poisonings). But the method, performed poorly in distinguishing between falls and road traffic injuries, both of which are characterized by similar injury codes in our datasets. While such stop gap methods can help derive additional information, hospitals need to incorporate accurate external cause coding in routine record keeping.

Seatbelt wearing rates in middle income countries: A cross-country analysis

In settings with low seatbelt use prevalence, self-reported seatbelt use estimates often lack validity, and routine observational studies are scarce. In this paper, we aim to describe the prevalence of seatbelt use and associated factors in drivers and front-seat passengers across eight sites in four countries (Egypt, Mexico, Russia, Turkey) using observational studies as well as to produce estimates of country-level and site-level variance. As part of the Bloomberg Philanthropies Global Road Safety Program, data on driver and passenger seatbelt use across four middle-income countries was collected between October 2010 and May 2011 (n=122,931 vehicles). Logistic regression and Intraclass Correlation Coefficient analyses for sites- and country-level clustering were performed. We found high variability of seatbelt wearing rates ranging from 4 to 72% in drivers and 3-50% in front-seat passengers. Overall, average seatbelt wearing rates were low (under 60% in most sites). At the individual level, older and female drivers were more likely to wear seatbelts, as well as drivers of vehicles transiting at times of increased vehicle flow. We also found that 26-32% and 37-41% of the variance in seatbelt use among drivers and front-seat passengers respectively was explained by differences across sites and countries. Our results demonstrate that there is room for improvement on seatbelt use in middle-income countries and that standardized cross-country studies on road safety risk factors are feasible, providing valuable information for prevention and monitoring activities.