It is sad that people put their life on the line for a minor saving. I do not drink and normally do not exceed 90-100 kmph under any circumstance, but still reach on time. Recently, the OECD noted that based on a survey of Road Safety Performance in member countries excessive and inappropriate speed is the number one road safety problem in many countries, often contributing to as much as one third of
fatal accidents and an aggravating factor in most accidents.
Broadly speaking, each 1 kmph reduction in average speed leads to a 2-3% reduction in injury accidents This is a modelling estimate only, it does not apply to every individual road. In real life, there is a range of effects, with the largest decreases being found on urban roads and the smallest on motorways.
In general, the number and severity of road traffic accidents rise as speed increases. Keep in mind that you have only 1 sec or less to respond. If you have say 10 secs, nobody would die except a suicidal person. There are many contributing factors (from OECD)
Firstly, high speeds reduce the time people have available to process information, to decide whether or not to react and, finally, to execute an action.
As braking distance is proportional to the square of the speed (v 2 ), the distance between starting to brake and coming to a complete standstill also increases greatly with increasing speed. The time needed is composed of two elements: the reaction time of the driver (approximately 1 second in standard conditions) and the braking time.
Third, the possibility of avoiding collisions reduces as speed increases. With a speed of 80 kmph on a dry road, it takes around 22 metres (the distance travelled during a reaction time of approximately 1 second) to react to an event, and a total of 57 meters to come to a standstill. If a child runs onto the road 36 meters ahead, the driver would most likely kill the child if driving at 70 kmph or more, hurt the child if driving at 60 kmph and avoid hitting the child if driving at 50 kmph.
The stopping distance also depends on the type of pavement (its friction coefficient) and the condition of the road. Stopping distances are much higher on wet roads than on dry roads. As an example, at 60 kmph a driver needs around 46 metres to come to a standstill on a wet road, an additional 10 metres over the distance required when stopping from the same speed on a dry road.
Even when speeding is not the decisive cause of an accident, the severity of injury is highly correlated with the vehicle speed at the moment of impact. The effects follow the rules of physics regarding the change in kinetic energy that is released in an accident. The relationship between serious injury accidents, fatal accidents and speed has been modelled by
Nilsson and is commonly illustrated by the "Power Model". Based on the Power Model, a 5% increase in mean speed leads to approximately a 10% increase in all injury accidents and a 20% increase in fatal accidents. Similarly, for a 5 % decrease in mean speed there are typically 10% fewer injury accidents and 20% fewer fatal accidents.
the visual field of the driver is reduced when the speed increases. At
40 km/h, the driver has a field of vision covering 100°, which allows obstacles on the roadside, or other potential hazards, to be seen. At 130 km/h, the field of vision covers around 30°, which reduces considerably the capability of the driver to assess potential danger.
Last edited by Samurai : 30th April 2007 at 11:59.
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