Road Traffic Injury Prevention
Accident remedial measures are actions undertaken to correct perceived or actual deficiency or risks in road traffic to improve safety. A WHO 2004 report indicates that about 1.2 million people are killed annually the world over and forecast that by “2020 road accident will be the second cause of death if the growing problems are not tackled” (WHO 1999) . Currently in the developing world it is the second largest cause of death after HIV Aids. Statistics indicates that on the average, the total cost of road accident is estimated to be about 2.5% of the Gross National Product of many nations. The Dft report (2009) indicates that accident place a huge economic and social cost to countries in terms of personal injury and damage to property. The above indicates that there is the need for a wide range of accident remedial measures to be adopted to curtail the risks of motorisation and reduce human suffering and social cost. To be able to target the appropriate remedial measures to tackle this challenge, a good accident data system will be needed to determine where accidents cluster and permit decision makers to prepare and identify priority areas that need the most attention. There are various ways by which this can be carried out such as ranking site by actual number of accidents (frequency) or rates of accidents occurrence (eg numbers per kilometre travelled) or the cost of the accident.
The merits associated with using numbers is that it has the ability to portray actual injuries or death and makes the data easy to relate to and the actual impact known and understood even by lay persons, example media men in reporting road accidents to the public are more comfortable using numbers (frequency) to rates and it appeals to the public than using rates. In this sense it is argued that it is easier to communicate to stakeholders and the public using numbers than rates. This also enables sites to be ranked in terms of absolute number of casualties and road safety interventions targeted at those sites can be supported by politicians who may not have in-depth knowledge on rates since numbers are easier to understand than rates.
Accident numbers refer to accident occurrence in a given stretch of road at a period of time. The use of numbers to set target are mostly used by practitioners because it allow the use of statistical models to determine significant relationship between dependent variable and a number of explanatory variables and rates calculated to compare risk level. This result can be used to predict effects of the accident and identify the key variable, example speed, alcohol that causes the accident and appropriate intervention adopted to mitigate impacts.
One of the arguments against using numbers to set target for safety measures is that a change in the number of occurrence of accidents due to low flow of traffic will alter numbers even though the level of the risk may remain the same thereby given a false impression. It can therefore be misleading particularly on low flow traffic roads where a single accident can greatly alter the rate, thereby giving a false interpretation which can have a big impact on the outcome.
Setting remedial measure using rates expressed in accident per number of population is recommended by most practitioners because it gives a value that can be easily related to and compared with local, national or international averages. Example comparing road death per 100,000 populations in say 2009 between regions or nations to compare performance for evaluation. The formula for calculating this is express as: Annual Accident rate = number of accident ? 100, 000/ number of population. When accident data is combined with exposure to calculate accident rates such as number of road accidents per 100,000 populations, a more informative comparative level of road safety is achieved at international level depending on the availability and comparability of these data.
It is widely argued in the transport sector that accident rate rather than numbers is a better performance measure in that the rates reflects the activity level and their relationship to the number of accidents. This tracks changes in the accident rates for a fixed volume of vehicle or human population. Example xyz accidents per 100,000 vehicles or population. By tracking the rate of accidents per vehicle or human population, decision makers can more accurately point out safety concerns or trends indicating potential safety concerns. It allows public risks to be calculated by extracting health risk rate from available population data such as number of deaths per 100,000 populations.
One of the arguments against rates in target setting is that it is nebulous to appeal to non-professionals in road safety in that it is expressed in technical languages, example Nigeria proposing to reduce the number of seriously injured per billion vehicle- kilometres by 15% by 2020 may be too difficult to comprehend by non-road safety professionals. Also, indicators for rates per unit of exposure need its corresponding exposure data, example population per kilometre which are most time not easily available immediately.
One of the disadvantage of using rates is that, regions with limited length of road network could register lower accidents due to average distance travelled and may give a false impression of the risks and the level of safety in those regions. Moreover, traffic risk is most appropriately measured using level of exposure data, example vehicle per kilometre travel which are not available in most countries and cannot not also be collected in the required level of details due to inconsistencies in definition of road network and different modes of transport used in different countries.
The use of both numbers and rates as an approach by the UK in setting national target can be helpful in that depending on the situation, quantity and reliability of data, information on accident rates may vary to be used for proper prioritisation, therefore, it is appropriate to use more than one type of accident analysis in ranking the problem to achieve a balance assessment of data. This data analysis can be based on accident rates, number of accidents or severity of injuries sustained or the cost of the accident. It is therefore appropriate to set targets in terms of absolute numbers and the rates so that where volumes traffic fluctuates the outcome can be amenable to treatment.
The use of both measures allows comparison of risks of road travel modes with the risk frequency of occurrence so that transport safety budgets can be allocated most effectively
WHO (1999); World Health Report: Making a difference, Geneva: World Health Organisation
WHO (2OO4) World Health Report on road traffic injury prevention, Geneva: World Health Organisation