SPEED ESTIMATES

Evening Post, Volume CIX, Issue 119, 22 May 1930, Page 10

SPEED ESTIMATES

FEET PER SECOND

NOT MILES PER HOUR

A JUDGE ON MOTORING

The opinion that there would be a great diminution in the number of motor accidents if drivers were to estimate their speed in feet per second, instead of in miles per hour, was expressed by his Honour Mr. Justice Blair to-day, when giving""judgment in. the Supreme Court in an action for damages. : "Although not relevant to the decision which I have just given," said his Honour, "the frequency of motor accidents justifies me in attempting to add something on tho subject"" of care in. handling motor vehicles which, perhaps, may help in reducing the number of motor accidents. "It is to be noted that in this case, as in motor cases generally, the evidence as to speed was given in miles per hour, and a great many people, experienced motorists at that, look upon miles per hour as -affording a proper indication of speed. Frequently on the hearing ofjnotor cases, I have asked witnesses who depose- to speed at miles per hour to indicate their speed in feet per second, but few motorists are able to do so. I have long held the view that if persons driving in cities or, for that matter, anywhere would, when driving, visualise their speed in. feet per second; instead of in miles per hour, there would bo v great diminution in tho number of accidents. FALSE IDEA OF SAFETY. "An entirely false idea of speed and safety is present when a driver is content to think of speed in terms of miles per hour. It is so easy to accustom oneself to drive in feet per second instead of miles per hour that there is no reason why every motorist and motorcyclist should not dp it. Indeed, there is something to be said for the proposition that until a driver can automatically convert miles per hour into feet per second, he is not as efficient as he should be. The simple mental process necessary.for this conversion is to add 50 per cent, to the miles per hour, knd tho result is speed in feet per second, correct within 2 per cent. In a crowded city street,-,15 m.p.h. may seem reasonable and safe, but its equivalent—23 feet per'second—puts the speed into a different category and calls for and, I believe, secures, added caution. PEDESTRIANS, TOO. "A pedestrian at 4 miles per hour moves at the rate of six feet per second, and when passing a footpath crowded with pedestrians, one of them, can in tho space of one second move outwards a distance of five or six feet, and be injured by a motorist travelling at, say, 10 miles per hour (15 feet per second). It appears to me, therefore, that if pedestrians as well as motorists appreciate what is meant by a. moving vehicle, it would add to tho care and respect each should have for the rights of the other. OVERTAKING VEHICLES. "The necessity for appreciation of what miles per hour mean in feet per second is apparent in the case of. one vehicle overtaking another," continued his Honour. "Iv order to pass another vehicle requires that a distance be travelled of at least 65 feet more ..than, the distance travelled by the overtakea vehicle.- If tho overtaken vehicle is travelling at 25 miles per hour (37$ feet per second) and .tho" overtaking vehicfe accelerates to, say, 30 miles per hour, tliciii-the :time'required to pass*, is sufficientto cover 65 feet at five miles •per hour (7J- feet per second). This means that the overtaking .vehicle requires seven seconds to complete th» passing operation. A third vehicle approaching these two vehicles,, at, say, 30 miles per hour but 100/ yards (300 feet) away at, the moment the overtaking commences would bring all three vehicles abreast in a fraction .over three seconds. The reason is that the third, vehicles and the overtaking vehicle are each travelling at 30 miles per hour (45 feet per second), and are thus using, up the distance between them at 60, -miles per hour (90 feet per ,second). . ■ ON COUNTRY ROADS. "Many accidents occur on country; roads due to plunging over banks at corners or narrow places. Many of these would be avoided if the driver had a due appreciation of his speed in feet per second. If a corner be rounded. at, say, 20 miles per hour (30 feet per second) and the road be narrow, onej half-second only is sufficient for that car to move 15 feet in the wrong direction. ABUSING THE BRAKES. "There have been from time to timS published tables showing the distance within which efficient brakes can bring a vehicle to'a standstill. One table I, have before me states that at 20 miles per hour a car equipped with efficient four-wheeled brakes can be pulled rip in 25 feet. There is a tendency to rely too much on brakes. And in all these tables the fact is overlooked that allowance must be made/for the mental reaction necessary before the motorist has his brakes full on.

'■'"Most authorities agree that one half second allowance at least must be assumed for* mental reaction," concluded his Honour. ."Applying this to the case of the perfectly-equipped vehicle at 20 miles per hour, it meana that at that speed 15 feot is travelled before the "brakes are on, and it is another 25 feet before the vehicle is stationary—4o feet in all. This again illustrates the wisdom of appreciation of speed in feet per second."