Chapter 8

Transportation medicine 

Every day around the world, almost 16000 people die from injuries, of which more than 20% are related to transport (World Health Organization 1999). Transportation injuries and self-inflicted injuries are the leading causes of injury-related deaths worldwide. The Global Burden of Disease study undertaken by the WHO showed that in 1990, traffic accidents were the world's ninth most important health problem and forecast that by 2020 they would move up to third place among leading causes of death and disability (Murray & Lopez 1996).

INTRODUCTION

Transportation safety is, therefore, a major social and public health concern in both industrialized and developing countries. Preventive measures range from design of infrastructures and construction of vehicles to the health status and behavior of vehicle operators. Investigation of transport accidents and traffic related deaths and injuries may call upon the entire spectrum of forensic sciences and medico-legal expertise.

ROAD TRAFFIC ACCIDENTS

In most industrialized countries the primary mode of transportation is the motor vehicle. More than 600 million motorized vehicles are registered worldwide: of these, one-third are in the United States (US) and another third in the European Union (EU) (Bureau of Transportation Statistic 2000, European Commission 2001). Deaths in motor traffic account for more than 90% of all transportation-related fatalities.

In 1998, road traffic accidents claimed 850 000 male and 320 000 female victims, the respective figures for the injured being 28.4 and 10.4 million (World Health Organization 1999). Of motor traffic-related deaths, about 85% occur in developing countries (Nantulya & Reich 2002). In these countries, the majority of those injured and killed are no motorized occupants and pedestrians, in addition to motorcyclists and bicyclists.

Conversely, in industrialized countries, vehicle occupants account for the majority of traffic fatalities, followed by pedestrians, especially the elderly, and bicycle riders. Despite the general downward trend observed in North America and Europe during the last decade, road traffic incidents are still the leading cause of death in many countries among 5 to 44-yearolds (World Health Organization 1999).

National agencies and international organizations provide data on road traffic accidents and related casualties. For instance, in the US, the National Highways Traffic Safety Administration (NHTSA) of the Department of Transportation provides detailed statistics on road traffic accidents based on data collected through the Fatality Analysis Reporting System (FARS).

Epidemiologic aspects

The International Road Federation (IRF) publishes annually the World Road Statistics with data on traffic accidents for more than 120 countries. The Organization for Economic Cooperation and Development (OECD), working closely with the European Conference of Ministers of Transport (ECMT), has developed the International Road Traffic and Accident Database (IRTAD) that gathers detailed data on road accidents for most of the member countries. Euro stat provides general data on transport and safety concerns for EU member states and every year publishes part of these in the booklet Panorama of Transport.

During 1998 there were in the US (270 million inhabitants, 215 million motorized vehicles) more than 6 million traffic crashes, in which 41 501 people were killed and 3 192000 injured (US Department of Transportation 2001a). In the EU (374 million inhabitants, 183 million motorized vehicles), the total number of road accident victims was 42 608 in 1998 (European Commission 2001).Tables 35.1 and 35.2 show the rates of killed and injured in road traffic accidents, and the percentage breakdown of casualties by road-user category in the EU countries and in the US in 1998.

The enforcement of preventive countermeasures at different levels varying from improvement in road infrastructure and car safety, to stricter legislation on drink driving, use of safety belts and air bags for car passengers and helmets for motorcyclists has resulted, in most industrialized countries, in a general downward trend in casualties since the 1970s.

In the EU, the total number of road accident victims has decreased by nearly 25% in less than a decade, from 56 414 in 1990 to 42 608 in 1998 (European Commission 2001). Greece is the only EU country where the number of road fatalities has not shown a downward trend during the last decade. In the US, the fatality rate per 100 million vehicle miles fell from 2.1 in 1990 to 1.5 in 2000 (US Department of Transportation 200 la).

Accident investigations: Mechanism and pattern of injury

Investigation of transport accidents aims to establish the sequence of events leading to a crash and requires a multidisciplinary approach to evaluate the role of the vehicle and infrastructural, environmental, and human factors. The collection of organic and inorganic traces from victim and suspect vehicle(s) is an essential part of the investigation of specific cases such as "hit-and-run" accidents.

Accurate determination of the causes and effects of vehicular accidents is necessary for forensic purposes but can also contribute significantly to improving road traffic safety. In Finland, beside routine police and medico-legal activities, 23 teams of the Traffic Safety Committee of Insurance Companies have investigated almost all road traffic accidents occurring in the country since the 1970s where driver and/or passenger of car has been killed. These teams include traffic police officers, vehicle and road engineers, and physicians (often a forensic pathologist), supplemented on occasion by psychologists or other experts on specific issues (Hantula 1987).

The identification, documentation, and interpretation of each traffic accident victim's injuries are a central task of the forensic pathologist at the accident scene and during the autopsy, and require a basic knowledge of their mechanisms of infliction. Pedestrian versus motor vehicle accidents In a collision between an upright adult pedestrian and a car, different impact phases occur and produce specific injuries (Table 35.6; Figures 35.5 and 35.6).

The primary site of impact is between the vehicle bumper and the lower extremities, mostly on their posterior aspect. Primary impact injuries include abrasions and contusions-at times patternedon legs, thighs, or buttocks, together with fractures of the tibia and fibula, and, more rarely, of the femur and pelvis. The site of these impact injuries depends on the type of car, possible lowering of the car's front end (from braking), and pedestrian height.

If the victim is walking at the time of impact, the bumper injury will be higher on the weight-bearing leg. The fracture of tibia and femur may present a wedge shaped fragment, the base which indicates the direction of impact and the front of the wedge the direction in which the vehicle was traveling. In small adults or children, the site of primary impact may be the pelvis or other regions above the center of gravity, when up to the head. In these cases, the victim is more likely to be run over, especially by a reversing vehicle.

FRONT-CRASH CAR ACCIDENTS

Frontal car crashes are the most common type of motor vehicle accident. Vehicle accident simulation with the use of dummies has made it possible to evaluate in detail the sequence of events during a car front crash.  

In the unrestrained driver and front seat passenger the deceleration force causes first an extension at the lumbar spine and a slide forwards with knee impact against the Fascia, then a move upwards and forwards of the body with impact of the crown against the roof frame and of the chest against the steering wheel (driver) or dashboard (front seat passenger). This is followed by a forward flexion of the cervical or thoracic spine, and a final strike of the head against the windshield or the pillars.

Other types of car crash accidents

Rear-impact crashes account for many civil suits for the whiplash syndrome caused by violent acceleration-deceleration of the cervical spine, which can sometimes be fatal if neck hyperflexion causes cervical spine fracture. In side-impact crashes, occupants are exposed to severe injuries of virtually any region of the body because restraint devices offer little or no protection and the thin lateral structures provide scant resistance to the impact crash.

Roll- over crashes are often fatal when occupants do not wear a seat belt since the head and upper trunk can protrude outside the car with severe regional injury. Occupants can be also completely ejected from the car, violently impact against the road surface, and eventually be crushed and struck by the vehicle they were in or other vehicle(s), resulting in severe head, chest, and abdominal injuries.

DRIVER STATUS

The identity of the driver at the moment of a vehicular accident is an issue that can be disputed, for instance when occupants are ejected from or relocated within the car or when their position is not documented at the time of removal from the car. In addition to vehicle dynamics, occupant kinetic evaluation and the study of patterned injuries and of trace evidence (pedal imprint, fibers, hair, blood and tissue from passengers) with their distribution in the vehicle may assist in clarifying this issue.

The direction of the seat-belt contusion or the steering wheel contusion on the thoracic region are among the most common and useful patterns of injury, together with air-bag injuries and recovery of their chemical components from the victim's body. The pattern of skin lesions caused by automobile glass can be useful, because tempered lateral and rear glass causes dicing lacerations, whereas laminated front glass determines deeper lacerations.

Motorcycle and pedal cyclist accidents can consist of single accidents, collision with other vehicles, or striking a pedestrian. The most common scenario for a motorcycle accident is sudden deceleration and collision, with the driver thrown forward and upward into a vehicle or a stationary object, whereas collision with a motor vehicle is the more frequent bicycle accident.

Other motor vehicle traffic accidents

Common injuries in motor bikers are head injuries (skull fractures including ring fractures and hinge fractures, brain contusion, and laceration), cervical spine fractures and atlanto-occipital dislocations, and leg injuries by primary impact or trapping in the motorcycle frame. In contrast, injuries to thorax and abdomen are rare.

Several studies have demonstrated the decrease in motorbike fatalities after the introduction of helmet laws; in a high-speed crash, however, blunt or penetrating injuries to the head or other body regions can be fatal. In a cold climate, such as that of Finland, snowmobile accidents (often caused by the effects of alcohol) on the sea and lake ice account for a relatively high number of traffic accidents involving middle-aged males, with drowning and hypothermia being the cause of death in more than half of the fatal cases.

That‘s all !