Dynamic Road Lighting Measuring System with Split Type Photocells

Abstract

In the past, in order to measure photometric characteristics of road and/or tunnel lighting inst allations, the so-called mobile laboratory has been used. For the mobile laboratory, however, to eliminate shadows of the vehicle over the photocells as much as possible, a long trailer, i. e. a long frame construction carried by two wheels, with a length of about 4 meters on which the photocells were mounted, was necessary. As a consequence, the driving speed of the mobile laboratory, consisting of a vehicle and a trailer, was limited to a relatively low level. This necessitated a strict control of the traffic on the road when the measurements were carried out. Based on a previous idea by J. Green et. al., an attempt was made to develop a measuring system by utilizing a number of pairs of two photocells in combination with an electronic data processing unit, one each in the front and another in the rear of the vehicle (instead of pulling a long trailer) with which the illuminance in the front hemisphere and in the rear hemisphere, respectively, were measured independently and supplementally with each other.
In this paper, firstly, the spatial and dynamic response of the pairs of photocells are analyzed in relation to their geometric construction, driving speed, and the mounting height of the luminaires. Secondly, requirements for the photometric performance of the pair of photocells in conjunction with performance of the data processing unit are discussed. Thirdly, componential error factors are examined separately as well as accumulatively. Finally, the performance of the spatial filter incorporated in the system, with which signals as to the driving speed can remotely be obtained, is described.