Factors in Car Accidents

Manawatu Times, Volume 62, Issue 258, 30 October 1937, Page 4

Factors in Car Accidents

Reaction and Stopping Distance ENGINEER’S ADVICE TO DRIVERS That speed was much less to blame as a cause of motoring accidents than the general public would have one believe, was an opinion expressed by Mr.' F. M. Hanson, road engineer attached to the Main Highways Board, when speaking at a conference of engineers in Palmerston North last evening. Whilo speed undoubtedly was a cause of accidents, there were many other important factors which motorists should not disregard and should have a full appreciation of. One of these was the distance in which a car could be stopped. Every motorist should know that stopping distance varied as the square of the speed. In other words, if at 30 m.p.h. the brakes brought a car to a standstill in 100 feet, then at 60 m.p.h., the distance would be 400 feet. Many motorists who touched 80 m.p.h. on the section of road between Masterton and Opaki—a real speedway—or on the Foxton-Sanson highway, or on the Canterbury plains, did not realise that if a sheep were to suddenly appear from behind a gorse bush 200 yards aAcad, they had no chance of avoiding a collision except by swerving and running the risk of overturning or hitting a telegraph pole. Another important factor in connection with stopping distances was the re action time or the period that elapses between the seeing of an obstacle and the taking of action. One had often heard drivers say they stopped immediately but reaction time and the laws of dynamics made such impossible. Reaction time varied with age and other factors but tests had shown that one second of time may well elapse between the sighting of a danger and the taking of action to avert it. During that one second a car travelling at 30 m.p.h. moved 44 feet before the driver either applied the brakes or moved the 6teering wheel. On the average bitnmenous surface the same car will have moved another 75 feet before it would be actually at rest, it followed, therefore, that with the sudden emergence of an obstacle at 30 m.p.h., a motorist was powerless to avoid a collision for three-quarters of a chain and for a further chain could only miss hitting it by swerving and not by the application of brakes. Even should only half a second elapse, a motorist could not start to swerve in time to avoid striking a child running on to the road 22 feet ahead. Mr. Hanson said he was doubtful if many motorists appreciated that but if they did make themselves conversant with the facts about reaction time and stopping distances, there would be safer motoring.