Driver Eye Height: Experimental Determination and Implications on Sight Distances

Without adequate experimentations, the Rules for road design, often refer to information, values and methodologies found in bibliographic references well consolidated: the driver eye height from ground is one of these variables. While the world periodically monitors variations of this parameter in Italy the value resists, unmoving, for some thirty years despite the changes, in time, of the technical characteristics of the national vehicular fleet and of the driver population. In previous papers (Capaldo, 2003, 2004) have been conducted experimental investigations in order to determine a reliable value regarding the driver eye height. The aim of this paper is to submit recent surveys for a significant percentage of passenger cars and to determine the statistical parameters for the set of measured values. This new analysis showed which value of driver eye height is still different from the value fixed in the Italian Rules and as this value difference has changed during the years 2003 and 2008. The results obtained have allowed to study the implications in road safety due to different values of the driver eye height. This height is one of the parameters needed to the determination of the minimum radius in the vertical crest. Marginally the measurement must be considered in setting minimum side distance of an obstacle to visibility in horizontal curves.