Vehicle Tests on Motor Roads

Abstract

HIGHWAY engineers are interested in tests recently made by the German road authorities on the comparative efficiencies of motor roads and ordinary roads. An abstract of a paper on the subject is given in Roads and Road Construction of August. The results of the driving efficiencies obtained in two approximately parallel roads joining Bruchsal to Bad Nauheim, a distance of about 91 miles, are given. One of these was an autobahn road and the other a State road specially constructed for long-distance journeys which had been greatly improved during the last four years. The latter road was comparable in layout and surface condition with a Class I road in Great Britain. The tests were made with an ordinary high-powered car. On the State road, the journey took 2¼ hours at an average speed of 44 miles per hour. On the motor road it took 1¼ hours at an average speed of 74 m.p.h. ; on the State road the average speed was only 56 per cent of the maximum speed of the car ; on the motor road it was 92 per cent. On a second journey undertaken on the motor road at the same average speed as that attained on the ordinary road, the petrol consumption dropped from 5·5 to 3·1 gallons. Considering that on the ordinary road 351 cars were met and 158 overtaken, exclusive of bicycles and pedestrians, the feeling of safety is much greater on the motor road as there are no oncoming cars to avoid. The tests were made with a 3·21 Mercedes car. It is concluded that on the motor road you always arrive quicker at your destination than is possible on the ordinary road and consume less fuel. On this road also the safety is greater and the stress to which the driver and car are subjected is much less. Further experimental results are to be carried out on speed trials with other cars.