Research On The Reasonable Spacing For Driver's Line Of Sight Delineation Facilities

The designing geometry parameters in existing highway technology criterions only assure the minimum safety for the vehicle's dynamics, at the same time, for the restrict of landform, some sections of road must under the design criterions, and add the ill route combination, it cause the contact of line type and traffic accident is consanguineous in the three factors (people, vehicle, road) which lead the traffic accidents.The delineation facilities can indicate the car's moving direction, show or warn driver the linetype's shake-up in frontage road, so it can prevent the traffic accident and pledge the car's safety. But only few studies about the material setting method in the all literature, there is only basical prescripts in the criterion, it have no reasonable setting warranty.This paper discuss all the study status about chevron and analyse the all study methods, author sum up the shortages of all setting methods, improve the shortage in calculating principle and method of chevron spacing. This paper base on six basic curves under different design speed according to the Design Specification for Highway Alignment in China, and take into account the five factors include the angle and distance of acute cone vision, scattering angle and distance of the vehicle lamp, chevron legible distance, driver's eyefocus location and deceleration distance when vehicle approaches the curve which under the situation of high speed, the goal is that four chevrons can be seen at the same time at the edge of the median of dual two-lane highway, take the five characteristic points of the basic curves as the chevron setting jumping-off point, according to the curve integral characteristic and applying the tangent off-set method, establish the model of chevron spacing, then choose the minimum as the reasonable spacing, so based on the reasonable setting space of the basic type curve under different design speed, the ultimate chevron spacing models are gained. At the same time, author gain the model about chevrons blockage in the different traffic conditions, it can validate the chevron's setting spacing for the certain traffic condition and linetype.There is no correlated principle about stud's spacing in existing criterions, so the rationality of spacing is uncertain. Base on it, this paper advance two setting principles of the best curve curvature apperceive and studs in a line in driver's eyes, and take into account the driver's vision characteristic, the car's lighting capability, the two relationship models are built. The one is between spacing which four chevrons always in driver's view and curve radius with the motive of basic delineation; and the other is between spacing and curve design speed with the intent of the studs continuous in a line in driver's eye. Then the rational setting mode is analyzed and discussed according to the characteristic of the reflecting and unreflecting studs, economy and traffic safety status.The setting models of chevron and stud are scientific, so it can offer the advice and reference for the existing criterion.