I DRIVE SAFELY

Wanganui Chronicle, Volume 79, Issue 279, 25 November 1936, Page 10

I DRIVE SAFELY

THE REGULATION OF SPEED (The following article is taken from I a booklet published by the Interna- | tional Harvester Company in an endeavour to prevent the number of highway accidents that, are at present | taking such a tremendous toll in life and property). Truck manufacturers and experienced truck operators have for many years appreciated and recommended the economic value of keeping engine speeds within a safe operating range. By controlling or limiting the engme speeds, vehicle speed is also controlled. This is very desirable but must of necessity vary according to the type of service in which the vehicle operates. The demand for speed regulation has brought about Ihe sealed governor, which has been developed in many forms to a remarkable stage of efficiency considering the high engine speeds obtainable in the modern truck and bus power plant. Most operators of large fleets of trucks, and even many companies whose fleets include passenger cars employed by salesmen, equip their vehicles with governors limiting speeds to 20, 30, 40 and 50 miles an hour, according to the use to which the vehicle is put. This is being done for the simple reason that they will not have their vehicles unnecessarily abused, and of more importance, these companies know that high speeds account for about onequarter of all accidents and one third of all deaths resulting from driving errors. Sound business practice will not ; permit the economic losses sustained through costly damage suits involving both disabled horsepower and man power. 'the governor may easily become an item of standard equipment on every truck and car within the very near future unless all drivers of motor vehicles slow down and take their driving responsibilities more seriously.* Did you ever figure out how far you have to drive to' pass another car that is travelling 30 miles an hour? Assuming your speed is 40 miles an hour, and allowing safe distances for turning out and coming back into your own lane, you must travel 600 feet while the vehicle you are passing goes 450 feet. If the vehicle you want to pass is travelling 40 miles an hour and you pass It at 50 miles an hour, these distances are even greater. At those speeds you must travel 750 feet while the other car goes 600 feet. In other words it is equal to passing a stationary line of 38 average motorcars or 15 tractor-trailer units, each 40 feet long. These facts point clearly to the necessity of knowing that there are no oncoming cars for a long distance ahead. They should also convince us of the extreme folly of trying to pass a motor-car or another truck on a hill or on a curve where vision is obstructed. Another peculiar thing about speed is the fact that we never quite realise how fast we are going. If we drive along at a certain speed for quite a while it’s an easy matter unconsciously to increase our speed a few miles an hour. If we continue thus to accelerate, we soon find ourselves travelling at a dangerous rate, and this is often brought forcibly to our attention as we try to round a curve. Then halfway around the curve we find centrifugal force trying to turn us over, push us into the wrong lane, or off the road. The centrifugal force exercised bymomentum against a truck when we endeavour to round a curve at high speed is much greater than it is with a passenger car due to the higher centre of gravity and lower area or size of our vehicle. The laws of momentum react strongly against us in going around a curve because momentum wants to keep us going and going straight ahead. But when we try' to go around a curve, momentum operating against us becomes what is then known as centrifugal force, endeavouring to turn us over or shove us off the road. That is the reason the highways as well as railroads are banked at curves. Here is an example of the power of centrifugal force exercised on a truck weighing exactly' 15,000 pounds. Let us say we are driving this truck around a curve with a 500-foot radius. At 20 miles an hour our vehicle has to overcome a centrifugal force of only about 800 pounds. At 30 miles an hour that force has grown to approximately 1815 pounds, and at 50 miles an hour it is six times as great as at 20—more than 5037 pounds trying its best to overturn the unit or push it off the road. The friction between the tyres and the road and gravity are the only factors that keep us on the road. When the centrifugal force gets stronger than the forces of friction and fravity, over we go. When we find ourselves going round a curve at too high speed, and feel plainly the effects of centrifugal force, we naturally jam on Ihe brakes. It's the only thing we can do, yet this interferes with the effective control and steering of the car, because we have the vehicle under much better control when the rear wheels are not being retarded, but are actually propelling us around the curve. Those are briefly' the reasons why we cannot take liberties with the laws of momentum and centrifugal force. We may violate all the highway speed laws, but. we cannot violate those set up by nature.