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Communication Dans Un Congrès Année : 2008

Night-time visibility as a function of headlamp beam pattern and pavement reflection properties

Résumé

Road accidents at night are disproportionately high in numbers and severity compared to day, and the major factor contributing to this problem is darkness because of its great influence on the driver's behaviour and ability. To provide visibility to the driver in unlit areas, vehicles are equipped with headlamps which illuminate the road ahead. But in the presence of oncoming traffic, using low beam is compulsory to minimize headlight glare. Hence, designing headlamps which maximize roadway visibility for the driver and minimize the nuisance to other road users at the same time is a challenge. There are at least two different approaches to evaluate the performance of front-lighting systems. Those who design and manufacture headlamps use standard criteria which are directly related to the headlamp beam pattern. Some of these criteria are related to safety, such as the 3-lux line, and others are related to comfort, such as the beam spread. Those who use the headlamps (or their representatives) prefer criteria which are directly based on visibility range. They tend to focus on specific targets which are critical in terms of safety, namely pedestrians, pavement markings and signs. Implementing the latter, driver-oriented approach involves conventional traffic scenarios, which actually form the basis of the standard criteria of the former, vehicle-oriented approach. Visibility Level (VL) is the index which is most often used to assess the performance of lighting systems in a driver-oriented approach, not only for vehicle lighting systems, but for road lighting systems as well. VL is the ratio between the actual contrast of a target and the threshold contrast which is needed to detect to target. The threshold is usually computed by means of an empirical vision model based on laboratory data, and the operational viewing conditions are accounted for by means of a field factor based on road tests. In this paper we focus on the impact of the road environment on the VL-based performance of a lighting system. After reviewing the VL-based approaches to evaluate lighting systems, we present a night-time visibility meter based on measured pavement reflection properties, developed for road operators to evaluate the quality of service of their network in terms of the visibility offered to the drivers. We discuss how the data from this system could feed advanced front-lighting systems or infrastructure-vehicle cooperative systems to improve road safety at night.
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Dates et versions

hal-00399774 , version 1 (29-06-2009)

Identifiants

  • HAL Id : hal-00399774 , version 1

Citer

Eric Dumont, Roland Bremond, Nicolas Hautiere. Night-time visibility as a function of headlamp beam pattern and pavement reflection properties. VISION 2008, Oct 2008, France. 8p. ⟨hal-00399774⟩
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