Citation

De Boer J, Vermeulen D. Appl. Sci. Res. B 1952; 2(1): 1-32.

Copyright

(Copyright © 1952, Holtzbrinck Springer Nature Publishing Group)

DOI

10.1007/BF02919753

PMID

unavailable

Abstract

There is a distinct difference between American and European opinions about the most suitable beam pattern of motor-car headlights.The American point of view has been published in the Annexe to the Report 23 b of the I.C.I. 1939 by H. M. Magdsick entitled: "Some factors governing visibility distances with motor-car headlights". From visibility tests Magdsick and his collaborators concluded that the beam pattern realized in the sealed beam lamps should be superior to that of the European headlamps. In those tests a man size pedestrian dummy was taken as the visibility object. The visibility of the object was considered to be sufficient even if the object or only part of it could be discerned by silhouette. For safe driving, however, it is not sufficient to see that there is something present in front of the car. The driver should be able to estimate quickly and rather exactly the position of the object on the road, which is impossible if only part of the object is seen as a silhouette. The position of the object can always be estimated if the driver can see the line of separation between the road and the object. In consequence the lower part of an object is the most important with regard to visibility on the road. From this it follows that low test objects should be preferred. Visibility tests have been carried out for sealed beam lamps and European headlamps with objects of different sizes. These tests have not been made under actual driving conditions. Several phases of the passing of two cars have been tested while stationary. The results obtained with tall objects give a flattered impression with respect to traffic safety. Therefore objects should be used with a height not exceeding 40 cm. When sealed beam lamps and European headlamps are compared on account of tests executed with such objects, a slight difference in visibility in favour of the European headlamps can be stated.