Sustainable Road Safety

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In a sustainable safe road traffic system, infrastructure design inherently and drastically reduces crash risk. Should a crash occur, the process that determines crash severity is conditioned in such a way that severe injury is almost excluded.

Road traffic crashes cost too much

Every year more than a million people die in road crashes around the world, and about 70 percent of these deaths occur in developing countries. Pedestrians represent 65 percent of road crash deaths and 30 percent of them are children. In addition, a staggering 20 to 50 million people are injured or disabled each year in road crashes in developing countries, often pedestrians, motorcyclists, bicyclists and non-motorized vehicles occupants. This human tragedy is doubled by the catastrophic impact of loss of revenues and cost of medical care, as entire families can slip into deep poverty, wiping out the gains accumulated over years, and impacting, in turn, their communities. The emergencies created by road crashes also consume precious medical capacities in the health sector, and reduce the overall access to health care.

This silent epidemic is rapidly getting worse in developing countries. Research conducted by the World Bank estimates that global road fatalities will increase by more than 65 percent between 2000 and 2020, unless intensified safety interventions are implemented.

Sustainable Safety: an answer to the lack of road safety

A crash can happen to anyone. Everyone makes errors sometimes in an unguarded moment. Since humans make errors and since there is an even higher risk of fatal error being made if traffic rules set for road safety reasons are intentionally violated, it is of great importance that safety nets absorb these errors. Behold the Sustainable Safety approach in a nutshell!

The objective of Sustainable Safety is to prevent road crashes from happening, and where this is not feasible to reduce the incidence of (severe) injuries whenever possible.

The most important features of sustainable safe traffic are that latent errors in the traffic system (gaps in the system that result in human errors or traffic violations causing crashes) are, as far as possible, prevented and that road safety depends as little as possible on individual road user decisions.

The principles of Sustainable Safety

A set of guiding principles has been developed to achieve sustainable safe road traffic. These principles have all been based on scientific theories and research methods arising from disciplines such as psychology, biomechanics and traffic engineering. The results are formulated in the five Sustainable Safety principles of Table 1.

Table 1

Sustainable Safety Principles	Description
Functionality of roads	Monofunctionality of roads as either through roads, distributor roads, or access roads, in a hierarchically structured road network
Homogeneity of mass and/or speed and direction	Equality in speed, direction, and mass at medium and high speeds
Predictability of road course and road user behaviour by a recognizable road design	Road environment and road user behaviour that support road user expectations through consistency and continuity in road design
Forgivingness of the environment and of road users	Injury limitation through a forgiving road environment and anticipation of road user behaviour
State awareness by the road user	Ability to assess one’s task capability to handle the driving task

Functionality - This principle starts from the premise that roads can only have a single function (monofunctionality) and that they must be used in keeping with that function. The road function can, on the one hand, be ‘to facilitate traffic flow’ (associated with ‘through roads’), and, on the other hand, ‘to provide access to destinations’ (associated with ‘access roads’). In order to provide a proper transition between ‘giving access’ and ‘facilitating traffic flow’, a third category is defined: the “distributor road”. Sustainable Safety maintains these three main categories as the basis for a functional categorization of the road network.

Homogeneity - This principle states that, where vehicles or road users with great differences in mass have to use the same road space, speeds will have to be so low that, should a crash occur, the most vulnerable road users involved should not sustain fatal injuries. In addition, where traffic is moving at high speeds, road users should be separated physically.

Predictability - The benefits from this principle can be achieved by consistency and continuity in road design. This means that the design needs to support the user’s expectations of the road, and that all components of the design needs to be in line with these expectations. People have to be sufficiently capable and experienced to take part in traffic, but they also need to perceive what is expected from them and what they can expect from other road users.

Forgivingness - The starting principle of ‘man as measure of all things’ is that road users make errors and that the environment should be sufficiently forgiving for road users to avoid the severe consequences of these errors. If road users perform dangerous actions that could lead to crashes, they should have enough space available to recover. The principle of physical forgivingness (a forgiving roadside) can also contribute to reducing injury severity in crashes. Dangerous actions can also be affected by explaining and gaining support for the principle of social forgivingness. More experienced road users can, by means of forgiving driving behaviour (in terms of being anticipative or defensive), increase the room for manoeuvre of less experienced road users.

State awareness- This principle requires that road users should be able to assess their own task capability for participating in traffic. Task capability can be insufficient due to a lack of competence (e.g. because of a lack of driving experience), or because of – a state of mind that temporarily reduces the task capability (e.g. because of fatigue, or the use of alcohol or drugs).

Road Safety Elements

Infrastructure -Infrastructure planning and design is an important subject in Sustainable Safety. The principles of functionality, homogeneity and predictability have always been central. These three principles should be maintained in the future, with forgivingness (a forgiving road environment) added as a fourth principle concerning infrastructure.

Vehicles -Vehicle safety occupies an important position because the outcome of certain crash types is determined by crash speed and direction, and the protection that the vehicle provides (to the occupants and to crash opponents).

Intelligent Transport Systems -ITS are an important means of making road safety less dependent on the individual choices of road users. It is estimated that safety directed ITS may lead to 40% fewer fatalities and injuries.

Education -Traffic education in various forms plays an important, albeit perhaps underexposed role in Sustainable Safety up to now. By the term ‘education’, we mean teaching, instruction (aimed at specific roles in traffic, such as driver training) and campaigns. Within sustainable safe road traffic, it is important also to use people’s capacity to teach themselves.

Regulations and their enforcement -Regulation forms a foundation for the safety management of traffic processes, minimizing latent system errors, and restraining risk factors. Ideally, in sustainable safe road traffic people comply with the rules (spontaneously) without having to make an effort and without feeling negative about it. Unfortunately, spontaneous traffic rule compliance is far from being a reality and it is highly doubtful that it could be relied on in the future. The threat of penalties is needed to deter these road users not to comply with the rules, for instance by making the cost for non-compliance outweigh the perceived benefits of it.

Speed management -Speed and speed management are key elements in Sustainable Safety, because speed plays an important role both in crash risk and in crash severity.

Cyclists and pedestrians -Pedestrians and cyclists are vulnerable in crashes with other types of road users, because they are unprotected and also because other types of road users move at higher (sometimes too high) speeds. Crash speeds of motorized vehicles need to remain below 30 km/h in order for pedestrians or cyclists to survive the crash. This means that pedestrians and cyclists have to be separated from high-speed traffic.

Motorized two-wheelers -Motorized two-wheeled vehicles do not fit well into sustainably safe traffic, because they have a high vulnerability/ injury risk in crashes with other motorized vehicles, because motorized two-wheeled vehicles are quite often not noticed by others, and also because they often move at high speeds.

Heavy good vehicles -Dangerous heavy goods traffic almost always means a lack of safety for the other crash party. Fatal crashes already occur at very low speeds (particularly for the lighter collision opponent).

Young and novice drivers -Young road users behave more dangerously than other age groups. Generally speaking, the start of a driving or riding career corresponds with a relatively high risk of crash. The comparatively high risks are caused by a combination of lack of experience and age-specific (biological, social and psychological) characteristics.

Drink and drug driving -Driving under the influence of alcohol and drugs continues to be a persistent problem. The approach to combating drink and drug driving must take place at several levels: through legislation, police enforcement, education, punishment, rehabilitation and exclusion.

Road Safety Policy

The promotion of road safety should be priority for every road authority. Attention is generally focused on situations where a relatively large number of accidents and/or fatal accidents occur. Measures designed to tackle those accident concentrations should be based on thorough, objective analysis of the problems (determination of the origins). While accident analysis and investigations are very important this is a reactive approach to an existing situation. With sustainable road design the approach of road safety is pro-active: prevention is better than cure! A pro-active attitude by the road authority is essential to avoid situations that can result in accidents.