MOTORING

Nelson Evening Mail, Volume LXVI, 29 June 1935, Page 9

MOTORING

THE SKID DANGER IMPORTANCE OF ROAD SENSE ALLOWING FOR SURFACE VARIATIONS A valuable part of the skilful driver's 1 store oi' "road sei.ise”is his ability to observe road surface conditions, often subconsciously, and automatically to adjust his car’s speed accordingly. To such drivers a skid is a rare occurrence Conversely there is the thoughtless type of individual who carries on at unabated speed on a slipper road, and blames the surface if an emergency gives rise _ to heavy braking followed by skidding. Thus writes a contributor to the “Cape Times,” Cape Town. Possibly in time to come, road surfaces which are almost as safe when wet as when dry will be standardised. Even then, however, it still will be necessary to drive with caution in certain circumstances. For example, a road that is safe either when dry or thoroughly wet usually passes through an intermediate stage of slipperiness when light- rains have fallen and have mixed with the accumulated dust of a previous dry spell. When travelling along-an unfamiliar road in wet weather, the driver should be alert to notice any change of surface as indicated by the colour or texture of the road material. If in any rio.ubt as to the adhesion it affords, and if he be so minded, he quite easily can make, an impromptu test by means of the brakes, when the coast is clear, so as to ascertain whether or not if is safe lo continue at speed.

EMERGENCY TUSKS If too high a speed be maintained on a treacheious surface, created, for example, by the. sudden appearance of .mother *ehv!.’ may liec" isit.itc steering or braking in a way which, whilst perfectly safe on a dry road, will lead to disaster on one that is wet. Round a fairly sharp curve requiring, say, about half the steering lock of the average car to negotiate, there bemg no camber to complicate matters, a speed of 30 miles an hour probably would produce a centrifugal force sufficient almost to initiate an outward skid on a dry road, this being approximately the limiting speed for such conditions. But there are many surfaces where, on a wet day, adhesion is reduced to about half the “dry” figure. Assuming this to be tlie case, the maximum safe speed on the curve in question woiAd be cut down to about 21 miles an hour, the centrifugal force being proportional to the square of the speed. Safety will be reduced still further if there is a pronounced camber to assist the rear wheels in sliding towards the roadside on 'a righthand curve. A similar effect governs stopping distances. In an emergency the maximum retardation is obtained on the average car when the pedal pressure is nearly (but not quite) sufficient to •ausc 'he rear wheels to lock and slide, and therefore is dependent on the adhesion available between the tyres and the road. With reasonably good brakes a car can be stopped hi 100 feet from 4G miles an hour on a dry road. If adhesion be halved, owing io ram '.lie ear cannot be stopped in tl.is distance ud<:s i*s speed be i educed from -0 to ’h .mm.s an hour. L*?SS ADHESION—LESS STEEL Although extreme, these eas-'k are by no means imaginary, their point’., living that decfoascci adhesion -pi j duces . air enormous reduction in the limit nf speed that may be indulged in with .safety. If more drivers could be brought, in rea lise this, the number of inadvertent skids—often with uat •“tunate consequences—would be greetUv reduced. When crossing train lines cars differ considerably in their behaviour. Care should be taken not to run with all four wheels in the lines. On a dry day the car can be pulled out suite easily by a quick movement of the steering wheel, but in wet weather, when the rails become very slippery, the degree of steering movement, necessary is considerably increased, when a rear .vied skid ;s an extremely likely occurrence Reduced adhesion is liable I to be caused by ripples or other road surface irregularities, producing axle movements which may he converted into movements of the whole car. With an open throttle wheel spin may occur, when resistance to sideways movement is reduced practically to zero. Cars with stiff springs are least liable to this trouble, a good tip for winter driving I being to increase the damping effect of the shock absorbers "where possible. Equally important is to keep all tyres at their correct inflation pressures. THE SUDDEN GREASY PATCH At this season every year, and for the ■ next few months, many more or less serious accidents are caused simply | through cars being driven regardless of road surface conditions. Suddenly a greasy patch is encountered, and away goes the car on a four-wheel skid, com-. pletely out of control. In daylight, at any rate, trouble of this' kind -can > be avoided by driving with caution and keeping a sharp look-out for-any-changes-of surface. By night, naturally, the risky of being caught unawares is 'increased, j but here again, it can be reduced by.; slackening speed in accordance' with cirdj cumstances.. " , ; • J

On a slippery down-grade, where even mild application of the brakes may cause a skid, a good plan is to use the’ engine as a brake, changing down, if necessary, to increase braking effect. Finally there is the matter of correcting a skid which has commenced. • As .a rule only the rear wheels lose directional control, the car swinging round the steering heads; with the front wheels continuing in their normal course. The idea is to make the tail of the caV swing back in the opposite direction, this being done by steering into the.skid. In other words, if the hack of the car has begun, to slide inwards towards the nearside kerb, the steering should be given a sharp movement to the left in order to reverse the direction of Skidding,. An instant later, probably it will be,necessary to steer in the opposite direction to correct a slcid resulting from overcorrection. PSYCHOLOGICAL TESTS DRIVERS’ REACTIONS y Are you accident-prone? In. Britain there are 200,000 motorists who are more prone to accidents than the remaining 1,800,000 good drivers. You can find out just how good—or bad—a driver you are by testing yourself at the National Institute of Industrial Psychology. Aldwvch House Commercial firms now send voung drivers to he tested at the N.T.I.P. A successful candidate is entitled to n re-

ducod insurance rate. The writer watched three young commercial drivers undergoing psychological' tests. The tests wore carried out in darkness. The drivers were tested for reaction,; resistance to distraction, vigilance, 1 vision, visual co-ordination, and judg-< ment. j These are inherent qualities. If you) do not possess them no amount of experience can help you to acquire them. The young men sat with throe keys coloured red, yellow and green under their fingers. Red, yellow, and green lights appeared at irregular intervals on a screen. As each light flashed the candidates were asked to press the key of the corresponding colon . . , . - The time elapsing before registration was recorded' lo Lie nearest - cne-hun-jdredth of a second. In a sudden-emergency on the roads, a previous second may elapse before the driver reactA test of concentration was _ arresting. A picture of a beautiful girl in a bathing costume was flashed on the screen. She was lying oil a bed of pointed nails ! And all the in;e- these coloured lights danced on the edge of the screen and the keys clicked i:i response. Manipulative ability, road behaviour and confidence were tested in a dummy car placed b.cfcre a revolving roadway on a screen. The test lasted an hour, but two days elapsed before the young drivers knew he v i hey r ued.