STOPPING A CAR

New Zealand Herald, Volume LXXVI, Issue 23488, 27 October 1939, Page 11

STOPPING A CAR

A JUDGE'S ANALYSIS TIME FOR MENTAL REACTION POTENT FACTOR IN ACCIDENTS [by telegraph—ow.v correspondent] WELLINGTON, Thursday The ground covered by a motorist in the time occupied in mental reaction to an emergency was pointed out by Mr. Justice Blair in a reserved judgment delivered in the Supreme Court to-day. His Honor saying that an allowance in travelling speed must be made. Taking His Honor's estimate of twothirds of a second as the normal reaction period, a motorist travelling at 40 miles an hour will go 40ft. before the brakes are applied. "livery motorist knows, or ought to know, that in addition to the allowance necessary for Hie brakes to bring a car to a standstill, a further allowance must be made for the mental reaction necessary to appreciate danger and to telegraph that message to the feet and translate it into the muscular action of putting the brakes on hard," said His Honor. "Half a second is little enough allowance on that head. In my view a cautious driver should assume a necessary, allowance of twothirds of a second, which at 25 miles an hour is 25ft., but let me assume that the appellant is one of those fortunate drivers who can react to danger and have his brakes biting in half a second. That means a distance of ISft. is covered before the brakes commence to operate. Speed in Feet Per Second "T have assumed in appellant's favour that at a speed of 25 miles an hour and on a down grade he can bring his car to a standstill in the minimum required by the regulations for 20 miles an hour (.'3oft. a second) on a level road. On those two assumptions made in appellant's favour, it would require !oft. plus ISft.. a total of 58ft., to bring his car to a standstill. "I have analysed what the matter of speed when looked at in terms of feet per second means and involves, because it is plain to me the appellant did not, on his admitted speed, have due appreciation of the rate he was covering the ground. T have also purposely referred to the necessity for making an allowance for mental reaction, because ignorance of that necessity is, to my mind, a potent factor in motor accidents. Distance Covered "1 would recommend as the allowance for mental reaction a period of at least two-thirds of a second," continued His Honor, "and that allowance. when translated into the distance covered in the reaction period and before the brakes are biting, is the same number of feet as the car is travelling in miles an hour. "In other words, if a car is travelling at 20 miles an hour, then 20ft. must be allowed for mental reaction, at 30 miles an hour 30ft.. at 40 miles an hour 10ft.. and so on. If a car possesses brakes of regulation efficiency, at 20 miles an hour, that is. a 40ft. stopping distance, then a prudent driver should assume that to pull his car up at that speed he must allow 20ft. for mental reaction and 40ft. for his brakes to bring the car to a standstill, a total of 60ft."