Other Design Elements

Lighting

Sufficient lighting of roads and junctions can reduce accident risk at night. Around 35% of all reported accidents occur in the twilight or in the dark. The percentage is the same both inside and outside urban areas. The percentage of accidents in the dark is also higher for accidents involving pedestrians and accidents concerning vehicles run off the road [19].

The objective of road lighting is to reduce the accident rate in the dark by making it easier to see the road, other drivers and the surroundings of the road. It is important to provide uniform lighting of the entire carriageway; therefore lighting should be also selected according to the reflective properties of the pavement. Lighting implementation is necessary according to priority at junction areas, on roads around or approaching inhabited areas, and on roads with high traffic volumes and / or operating speeds.

Several studies have shown that the implementation of sufficient artificial lighting can reduce the number of accidents in the dark [98]. Moreover, the effect of road lighting has a greater effect on accidents involving pedestrians in the dark than on other accidents. Additionally, the effect of road lighting does not vary significantly among different road environments (motorways, urban and rural areas). Improving existing lighting also has a significant safety effect, by reducing the number of road accidents.

It should be noted, however, that the effect of road lighting may vary according to traffic and geometry characteristics of the road (road or junction type, traffic volume, speed limit etc.).

Roadside

Accidents occurring on the roadside, as a result of vehicles run off the road, are an important proportion of the total number of accidents. Constant obstructions (may cause significant injuries when such accidents occur. Roadside treatment aims at minimizing the probability of accident, through appropriate roadside configuration (roadside design, land use etc.) and limitation of constant obstructions. In case a vehicle runs off the road, the higher the roadside free zone is, the higher is the probability than the accident is avoided [70] [69].

An important focus for treatment of roadsides is to create a forgiving environment. This means that if vehicles do leave the road their impact with any furniture that has to be located within the ideal clear zone should not result in serious injury. This can be achieved in two ways – placing a barrier in front of roadside object to deflect vehicles away from it, or using passive materials (i.e. that will breakaway on impact). Collapsible lighting columns were an early example of the latter approach; more recently passive designs for supports for large signs and for gantries are being trialled.

Different restraint system designs utilise different levels of containment (e.g. N2 barriers will deflect cars but can be breached by heavier vehicles), and different working widths. Choice of type and siting of restraint systems to use at specific sites should take these characteristics into account. Restraint systems are very effective in reducing injury to car occupants but severe injuries do still occur. Growth in numbers of sports utility vehicles and light vans has also increased the proportion of vehicles not fully restrained by a standard N2 barrier. Containment is provided by the longitudinal members of the restraint system. With steel and wire rope systems these members are carried by individual supports; impact between two-wheeler riders and these supports can result in more serious injuries than where a continuous face is provided by the restraint system.

Severity of injury in roadside impacts can be mitigated by improving design of both vehicles and infrastructure. It is particularly important that improvements are designed consistently to make sure the two systems work together to provide the safest outcome.