Although all types of road user are at risk of being injured or killed in a road traffic crash, there are notable differences in fatality rates between different road user groups. In particular, the "vulnerable" road users such as pedestrians and cyclists are at greater risk than vehicle occupants and usually bear the greatest burden of injury. This is especially true in low-income and middle-income countries, because of the greater variety and intensity of traffic mix and the lack of separation from other road users. Of particular concern is the mix between the slow-moving and vulnerable non-motorised road users, as well as motorcycles, and fast-moving, motorized vehicles.
Poor people in low income countries are believed to be especially at risk from road crashes because they are more exposed. If injured, they often cannot pay additional and unexpected medical and funeral costs and the loss of a victim's or carer's income causes financial stress. In Bangladesh a study showed that among the Bangladesh poor, few of the victims were the head of the household, rather they were adult children who were the main income providers. Thus they were also more likely to have both elderly and young family dependants. In Bangalore in India the majority of poor households reported at least one person having to give up working/studying to care for the injured. Non-poor households were in many cases tipped into poverty as a result of a road injury of death.
According to the World Health Organization (WHO), in road traffic, risk is a function of four elements: exposure, the probability of a crash, the probability of injury and the outcome of the injury. Compared to other road users the vulnerable user group is particularly exposed to injury as they are not protected by a vehicle shell. In low and middle income countries the behaviour and mix of traffic and speeds creates even more dangerous conflicts amongst the different road users. Vehicle factors - such as braking, driving and maintenance as well as defects in road design and lack of traffic separation can also lead to an unsafe road environment for the users. In case of a road crash, if appropriate pre-hospital and emergency care are not provided, the result of injuries will be more severe and more lives will be lost.
There are clear regional and national differences in the distribution of road user mortality. Vulnerable road users - pedestrians and cyclists - tend to account for a much greater proportion of road traffic deaths in low-income and middle-income countries, than in high-income countries. In Delhi, India, for example more than 80% of the total number of fatalities is vulnerable road users of which pedestrians are the biggest group. In Thailand 70% of the road fatalities relates to motorcycles.
The type of traffic, the mix of different types of road user, and the type of crashes in low-income and middle-income countries differ significantly from those in high-income countries. Their traffic patterns have generally not been experienced by high-income countries in the past and so technologies and policies cannot be automatically transferred from high-income to low-income countries without adaptation. A good example of this provided by that of Viet Nam, where rapid motorization has occurred as a result of the proliferation of small and inexpensive motorcycles (95% of registered vehicles).
Children, elderly, and disabled people are particular vulnerable, as their physical and mental skills are either not fully developed or they are especially fragile. Children and older people are often overrepresented in traffic fatalities.