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                                       DRIVING TIPS

Braking Distance

Reaction times for a racing driver will be around 0.25 sec but perhaps over one second for an older person whose mind and legs are not as agile. 

The best braking deceleration is generally taken as 1g - the retardation due to gravity if you throw a stone into the air. Some cars can brake more fiercely than this (1.0-1.2g) as tyres key into the road surface rather than rub across it. 

The recommended stopping distance is thinking (reaction) distance plus braking distance. The Highway Code assumes that the average driver has a reaction time of 0.7 seconds to think and then operate the brake pedal. At 30 mph, this is 30 feet, 40 mph is 40 feet etc. Braking at 1g from 30 mph stops the car in 30 feet. In practice, Highway Code distances are calculated at 0.7g (43 feet from 30 mph) to allow for a gradual build-up to maximum braking. A racing driver with a 0.25 second reaction time and good road car brakes might stop from 30 mph in 11 + 25 = 37 feet. An older person with a one-second reaction time and a normal car would need 44 + 43 = 87 feet. 

Braking distances increase as speed x speed - so 43 feet from 30 mph means 172 feet from 60 mph. So keep your distance from the car in front. On fast roads you should leave at least two seconds between the car in front and your car passing the same spot - more if it is slippery.

www.fsmotorist.co.uk



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