It may be surprising for people to know that crash risk when speeding is similar in effect to that of drink driving.
In the road environment, a driver or rider is considered to be speeding when:
- travelling at excessive speed, that is, above the posted speed limit
- travelling at an inappropriate speed, that is, too fast for the traffic, road and/or weather conditions.
The driver may feel that speeding means a shorter travel time. However, speeding will also increase:
- the risk of a very serious crash (including fatal)
- the risk of serious injuries and fatalities
- the risk of fine, demerit points and loss of licence
- fuel consumption
- vehicle emissions.
Travelling at a safer speed doesn't take that much extra time. Travelling at 100 km/h instead of 110km/h over a distance of 10 km only takes about an extra 30 seconds.
The impacts of speedingThe Centre for Automotive Safety Research (CASR), University of Adelaide, has shown that the risk of crashes and the severity of resultant injuries increase rapidly and disproportionately with increasing speed, on both urban and rural roads. At 65 km/h, the risk of crashing is double the risk at 60 km/h. On rural roads, the risk doubles for each 10km/h a vehicle travels above the average traffic speed. Excessive speed and inappropriate speed are often important factors in single vehicle crashes such as hitting a fixed object and rolling over, particularly on open country roads. |
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Speeding and Stopping Distance
Higher travelling speeds increase the risk of crashes through loss of control and injuries by increasing reaction distance, braking distance, impact speed and crash energy.
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Speeding and stopping distance |
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Total stopping distance |
The distance your vehicle travels from the time you see an event occurring to the time the vehicle is brought to a stop. It is a combination of reaction distance and braking distance. |
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Reaction |
The distance travelled by a vehicle while the driver realises the need to brake and actually physically starts to apply the brake. |
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Braking distance |
The distance travelled by the vehicle once the brakes have been applied.The braking distance increases at a greater rate than the increase in the speed you are travelling – if your speed doubles, your braking distance will increase by 4 times; if your speed trebles, your braking distance will increase by 9 times. |
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Impact speed |
The speed at which the travelling vehicle crashes into another object. Even if the brakes have been applied before the crash, impact speed can be enough to cause serious injury or death.
Small reductions in travel speeds can make a big difference to impact speeds which, in turn, have an effect on the risk of death or serious injury. For example, at the point where a vehicle travelling at 50 km/h could stop under emergency braking conditions (and perhaps just avoid a crash), a vehicle travelling at 60 km/h would still be travelling at more than 40 km/h. |
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Crash energy |
Higher travelling speeds result in higher crash speeds which produce disproportionately more severe injuries. The severity of injuries sustained in a crash is, other factors being equal, always dependent on the energy that is dissipated in the crash. Crash energy increases at a much faster rate than collision speed. As speeds increase, serious injuries are usually found to increase at a faster rate than less serious injuries. |
What you can do about speeding and other road users
Speeding poses a serious risk to the safety of other road users as well as the offending driver.
Pedestrians, especially children and the elderly are our most vulnerable road users. Cyclists often have to share the busier road environment. Motorcyclists, equestrians and other vehicle drivers are all affected.
Other road users can easily underestimate the approach speed of a vehicle that is travelling much faster than other traffic. They may then endanger themselves by moving into or across the path of the speeding vehicle.
The risks to other road users are much greater than most people appreciate – don’t speed.
Initiatives for Safer Speeds
Actions to achieve Targets 2.9 and 2.10 in South Australia’s Strategic Plan include:
- Introducing default speed limit of 50 km/h in built-up areas.
- Lowering speed limits on road sections in the Adelaide Hills to 80 km/h.
- Reducing speed limits from 110 km/h to 100 km/h on rural roads.
Initiatives in the South Australian Road Safety Action Plan 2011-2012.
