How Speed Influences Car Accidents

Safety - 19 April 2019

The speed of motor vehicles is at the core of the estimated 1.2 million people that are killed and the 50 million that are injured in road crashes worldwide each year. Figures are expected to increase by 65% over the next 20 years in the absence of a real commitment to prevention, says the World Health Organisation (WHO).

In its 2018 World Report on Road Traffic Injury Prevention, WHO describes road traffic systems as the most complex and dangerous of all the systems people negotiate daily, and traffic speed as a double hazard that influences both the probability of a crash as well as its consequences.

What Does Research Say About Speeding?

Empirical evidence from global speed studies shows that:

• An increase of 1 km/h in mean traffic speed typically results in a 3% increase in the incidence of injury crashes and an increase of 4–5% for fatal crashes.
• A decrease of 1 km/h in mean traffic speed will result in a 3% decrease in the incidence of injury crashes and a decrease of 4–5% for fatal crashes.

Speeding is regarded as a factor in nearly one-third of all fatal crashes, it says.

Intensive research by the Council of Scientific and Industrial Research (CSIR) in South Africa from the mid 1970s to the mid 1980s, found that the relationship between the crash rate and the speed limit was almost linear.

What is Speeding and Why Speed Limits?

Speeding is defined as exceeding the posted speed limit and driving too fast for the prevailing conditions.

According to the WHO report, speed limits are crucial to governments and local authorities that have to balance the need for mobility with safety. These limits are based on a set of “optimally safe” parameters that combine safety, mobility and environmental parameters, as well as the impact of the set speed on the population near the road.

Slower speeds, for example, are set in areas where motorised traffic mixes with pedestrians or where non-divided roads increase the possibility of frontal collisions

Why is Speeding so Dangerous?

Road safety advocacy forum Arrive Alive is unequivocal in its conviction that speed increases crash severity because it:

1. Reduces time to stop the vehicle
2. Extends the travel distance/reaction ratio
3. Reduces ability to steer around curves or objects

Variable Travel Speed/Impact Speed Ratios 

Based on the average driver’s reaction time of one second and stopping distance on a dry surface of 90m on encountering a pedestrian 60m ahead, travel speed/impact speed/fatality ratios would be as follows:

• 110km/h
  • Impact speed will be 80km/h with a 100 % fatality potential for the pedestrian
• 100km/h
  • Impact speed impact will be 60km/h and 70% fatality potential for the pedestrian
• 90km/h
  • Impact speed will be 30km/h with 7% fatality potential for the pedestrian

Note: The risk to car occupants are equally variable with an impact speed of 80km/h increasing fatality potential by 20 times versus an impact speed of 32km/h

How Speeding Affects a Vehicle

Speeding adversely affects the mechanical efficacy of a car. Safety devices such as air bags and safety belts are severely compromised at high speed. The greater strain placed on tyres and brakes increase their risk of failure too.

The Main Influences that Contribute to Speeding

Research into fatal crashes shows a significantly higher incidence of speeding among intoxicated drivers than sober drivers.

Gender and age are also key. Young male drivers are most prevalently linked to fatal accidents where speeding and alcohol are present.

Driving Habits to Keep You Safe on the Road

There are good driving habits that will significantly improve your safety of the road, such as:

• Use the 2-3 second rule to maintain a safe following distance from the vehicle ahead of you. Increase this to 4-6 seconds in bad weather conditions, driving at night, on gravel or when towing a trailer.
• Reduce your speed to the road, traffic and weather conditions because posted speed limit applies to ideal conditions that are subject to these changes.
• Maintain a safe constant speed and avoid weaving in and out of lanes.
• Always have an escape route - a space to move your vehicle if your immediate path of travel was unexpectedly blocked. Always be aware of the position of other vehicles sharing your path.
• Do not “overdrive” your headlights at night.
  • Do not drive too fast for the distance you can stop in.
  • If you cannot stop in the distance you can see on a dipped beam, you could potentially hit potholes, tyre casings, or worse still, pedestrians.
  • Always be ready to adjust speed and slow down so that you can stop within the visible distance.

Follow the SMART driving tips from Phillip Kekana, road safety ambassador and racing legend. Remember, road safety begins with you, the driver. If you haven’t had your vehicle safety checked, pop in to your Supa Quick fitment centre for a free assessment.

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