THE REFINEMENT OF DRIVERS’ VISIBILITY NEEDS DURING WET NIGHT CONDITIONS

摘要

The purpose of this project was to develop a specification for the minimum retroreflectivity ofpavement markings in wet nighttime conditions. In order to establish this specification, theperformance of four retroreflective pavement marking materials in wet-night conditions wasevaluated. The performance of the pavement markings was evaluated by driver participantsunder simulated rain conditions using a similar protocol to studies that have already beenperformed at the Virginia Tech Transportation Institute. The performance of the markings wasverified based on the participants’ ability to detect the end points of the markings in both rainyand clear conditions.The conclusions from this investigation indicate that: 1) The materials developed over recentyears show an improved performance over those tested previously. These materials provideadequate performance through improved technology and performance. 2) The log-linearrelationship found previously is functional for the data provided. Two models were developed.The model with no intercept provides a more constrictive boundary at low levels ofretroreflectivity. 3) A retroreflectivity value above 250 mcd/m2/lx provides limited return interms of detection distance. 4) A specification limit of 150 mcd/m2/lx will provide adequatevisibility for 55 mph in dry conditions and 40 mph in wet conditions using standard dryretroreflectivity measurements, and 1 in/hr measurements for the wet conditions. This valueshould be the minimum maintained over the life of the marking. 5) The retroreflectivityspecification for a white and a yellow material should be equal. 6) The rumble stripe showed asignificant recovery time improvement over the other tested materials.This study recommends a minimum retroreflectivity of 150 mcd/m~2/lx for white and yellowpavement markings in both dry and wet nighttime conditions.