PastImperfect -The Danger of Hills:To early motorists, hills were something to be dreaded - both ascending and descending.
When climbing a hill, the danger was that the car would come to a stop and, unable to ascend further, would start to run away backwards on the driver. Many were the early accidents and indeed fatalities caused by a car slipping backwards down a hill and dropping a wheel over the edge of the road or hitting a pothole or rock which jerked the steering out of the driver's hands with disastrous results.
To counter this situation many vehicles were fitted with a sprag - a bar fixed to the chassis so that it pivoted from the chassis at one end and was pointed at the other. In the event of the car slipping backwards and out of control, the driver would quickly let down the sprag so that the pointed end would dig into the road.
Failure to do this quickly usually meant that the runaway car developed enough momentum that it pole-vaulted over the sprag rendering it useless and possibly causing the car to overturn.
Even experienced drivers such as pioneer racing drivers Charles Jarrott, Charles Rolls and SF Edge recounted finding themselves in serious trouble on hills. The situation was usually exacerbated by the tyre or "spoon" brakes being likely to tear the tyres clean off the wheel rims if applied too hard. The trouble was they were usually ineffective unless applied hard.
Charles Rolls found early cars very top-heavy and in particular a ¾hp Peugeot which he owned in 1896 used to "sway terribly when going downhill". He recalled the car "literally jumping from one side of the road to the other . . . there was a very strong smell of burning when we stopped, and all the brake leather was burnt up."
The other problem which hills presented was, of course, that the car might not be able to climb them. Passengers who travelled regularly in cars became adept at leaping off at just the right moment to reduce the load, and quite possibly to add their muscle power to the efforts of the overburdened engines. Having reached the top and managed to avoid falling backwards out of control, the next likely problem was brake failure.
Charles Jarrott recalled reaching the top of a hill in Kent when suddenly his brake rod snapped. "I knew that to apply the brake shoes which operated directly on the tyres would have the effect of wrenching the tyres from their rims and would result in a bad accident. I decided to attempt to reach the bottom in safety, minus brakes. We took the whole width of the road to get around the first corner."