The Ministry of Transport, Public Works and Water Management is considering the feasibility of dynamically switching the lighting on motorways. This would provide under all traffic and weather conditions adequate illumination levels without illuminating the road unnecessarily brightly. This has been put into practice in a test conducted under contract of the Ministry of Transport, Public Works and Water Management, Transport Research Centre into the effect of dynamic illumination of motorways on driving behaviour and traffic safety. The first step was to establish on the basis of a scene analysis a preliminary switching schedule. Besides the normal level of illumination (100%) a reduced (20%) and an increased level (200%) was employed. When it becomes dark, at least the reduced level is switched on. For normal to high traffic volumes the normal level is switched on. as it is equally under unfavourable weather or traffic conditions (precipitation, slipperiness, roadworks in progress). The 200% level will be employed relatively infrequently and in particular for special traffic and weather conditions (for example during rain when traffic volumes are high) for fog or in the case of serious accidents. This preliminary switching schedule was employed in the test, during which its effect on driving behaviour was examined. The results demonstrated that the normal level of illumination resulted in minor adaptation of behaviour: average speeds increased somewhat (ca. 0.7 km/h) and the number of critical situations (short time headways, short TTCs) increased by a maximum of 1%. Taking into account also the positive effect of conventional lighting on traffic safety known from the literature, no negative effect on traffic safety is anticipated from these adaptations of behaviour. Differences between 100% and 200% were not reflected in driving behaviour for the combination of high traffic volume and precipitation. Other situations for which the preliminary switching schedule prescribed are relatively rare and the benefit of a higher level of illumination in such situations is considered to be limited. An inquiry among motorists' showed that the concept of dynamic illumination of motor ways was highly supported. There is absolutely no evidence to support the contention that the reduced level of illumination will under favourable circumstances be perceived as being too low. A cost-benefits analysis was addressed to the relationship between the installation costs of DYNO (20-100-200) for the pilot location and the energy and environmental costs (CO2 emissions from the power station). It emerged from this that for the system from the pilot project both the installation costs and the energy and environmental costs were higher than for a conventional installation. This system will therefore be unable to recover its investment on the basis of energy and environmental costs. When the DYNO system is equipped only with the reduced and normal lighting levels, the installation costs will still be higher than for a conventional installation, but the energy and environmental costs will be lower than for a conventional installation. Due to this the system can in principle recover its investment on the basis of energy and environmental costs. This is in line with the government's policy of reducing CO2 emissions. The payback period will depend strongly on the local situation and the tariff structure in which the system is employed. When installing or replacing lighting along motorways t, the recommendation is to consider employing a DYNO 20-100 system instead of conventional illumination. The reduced level used for this should be 0.2 cd/ml and the normal level 0.7 to 1.0 cd/ml (corresponding to the level that would have been selected for the road section in question for conventional lighting). The proposal for the final switching schedule is that in darkness the normal level should be switched on, except in the case of favourable weather conditions and low traffic volume: under those circumstances the reduced level will be switched on. The switching criterion proposed for transition from the normal to the low level is a volume of 800, and for the transition from the reduced to the normal level a volume of 1100 vehicles per hour per traffic lane. (A)
Samenvatting