Physics

Braking Distance and Reaction Time



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Few of us with a drivers licence would not be aware of the horrific statistics describing automobile accidents and while causes are often a combination of circumstances leading to the conclusion speed plays a dominant role in the severity of any given vehicle accident. Large trucks for example cannot decelerate to a stop from 60mph within the same physical distance as a car moreover individual drivers respond to sudden stimuli in varying degrees of relative time. A momentary distraction from focus on the road ahead can be fatal moreover as drivers become more complacent over time the process of anticipating and preparedness for a sudden evasive manoeuvre seem to diminish with time.

We humans require time to process information before committing ourselves to a course of action. Typical human reaction time can vary from 0.2 to 0.25 seconds; this reaction time can significantly increase with age, alcohol, drugs, fatigue, a neurological disorder, indeed many diverse causal influences can add to the average reaction time above. When combined with some additional contributing factors such as vehicle brake condition, road surface conditions (wet, dry or slick for example) from the moment of deceleration to full stop for a medium size vehicle travelling at 100kph (62mph) is around 160m (525'). Increase speed to 110kph (68mph) braking distance increases to around 195m (640')

Consider a vehicle travelling at night using headlights on hi-beam illumining the road out to a distance of 160m. If this vehicle moving at a speed of 180kph (112mph) it will require a distance of slightly more than 196m (646') and this is farther than the driver can see in the headlights ahead. While this looks obvious to the reader it is not uncommon for foolish people to drive even beyond this speed and it usually spells big trouble should something be in the way, or one could at least hope for a staggering fine from traffic enforcement authorities!

Time management means efficient use of available time to achieve maximum possible productivity and often includes multitasking. Your motor vehicle is definitely not the place to be multitasking yet each day we all see drivers touching up their makeup, chatting away on their cell phones or even trying to read a paper on their way to work. Fatalities often occur due to the slightest lapse such as looking down to change your music station, insert a CD or look for something in the glove compartment. This puts a considerable weighting on the drivers need to remain fully alert while remaining at or under a posted speed limit depending on conditions such as reduced visibility caused by fog, water on the road and the like.

The saying speed kills is absolutely correct when considered against how many road vehicle accidents would not have been fatalities had speed not been excessive!

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