SMART TOOLS FOR TRAFFIC LAW ENFORCEMENT: SPEED LAW ENFORCEMENT

Speeding can cause fatal accidents. Thousands of people are killed in
vehicle accidents on South African roads, mainly as a result of the remarkably casual attitude by drivers towards law compliance, with speed as one of the ain contributory factors.  Around the world speeding is one of the biggest road safety problems.

Article and photos by Kotie Geldenhuys

A number of studies have found that there is a strong relationship between speed and crash rates.  The relative risk of being involved in a casualty crash was found to approximately double for each 5 km/h increase of free travelling speed. Excessive speed can also contribute to judgment errors by other motorists. 

In a study conducted by the HSRC in 2003 it was found that a decrease of 1 km/h in the mean or average vehicle speed in rural areas resulted in a decrease of nine fatal accidents and 120 accidents per month. During the period of this study an estimated 12 500 lives were saved due to about 140 000 fewer accidents. It should be noted that during this period there were also very high levels of self- discipline and self-regulation among South African road users, accompanied by a high level of law enforcement. Similar tests done by the Department of Transport and in the UK in the 1990s achieved the same results.  A study by the University of Adelaide found that the risk doubled for every 5 km/h above 60 km/h. One reason for this increased risk is reaction time (the time it takes between a person perceiving a danger and reacting to it).  The reaction time of a driver who is distracted by listening to loud music, using a cellphone or who has consumed alcohol, may double.  The braking distance of a vehicle depends on various factors such as the slope or grade of the roadway and the frictional resistance between the road and the vehicle's tyres.

Most at risk when speeding
Twenty-four studies conducted worldwide have shown that pedestrians are most at risk of being injured or killed in road accidents. Passengers are the second most vulnerable, while drivers account for a small share of fatalities (less than 10% in most countries). Only Botswana, South Africa and Zimbabwe show more than 20% driver deaths.     

Impact of speed when hitting a pedestrian
Due to the fact that pedestrians are much lighter than vehicles, they have little effect on the speed of vehicles. One study, of which the results were provided to SERVAMUS by the JMPD, found that if a vehicle that travels at    65 km/h starts braking, its impact speed is approximately 8.1 m/s, meaning that the impact lasts only about 0.025 s. Once a pedestrian has been hit by a vehicle the probability of serious injury or death depends strongly on the impact speed. Reducing the impact speed from 60 km/h to 50 km/h almost halves the likelihood of death.


Speed and road works
The road works on South African roads are frustrating to everybody. Despite temporary speed signs, drivers proceed much faster than they are supposed to, through these construction sites.  The yellow temporary speed signs at road works do not indicate the suggested speeds, they are the legal speed limit and have been erected for a reason - lane width is usually reduced and drivers could easily lose control over vehicles and cause accidents that could easily result in a road worker's death. Speed camera enforcement has contributed to a decrease of 55% in accidents happening in the construction area between Maraisburg Road and the Soweto Highway on the N1 during April 2009, compared to March 2009.    

Speed cameras
To address speeding, driver behaviour must be changed and this can be done through a combination of education and enforcement. But is the use of speed cameras the best way to effect this change? “Yes,” was the immediate answer of  Dir Gerrie Gerneke, Head of Licences, Prosecutions, Courts and Electronic Enforcement of the Johannesburg Metro Police Department (JMPD). By evaluating South African speed camera programmes he concluded that speed cameras reduce road deaths and injuries.

Speed cameras deter drivers from speeding through detection and appropriate punishment, based on accurate and reliable speed measurement.  When drivers receive a speeding infringement, the majority subsequently tend to drive at reduced speeds.

In New Zealand, Mara et al (1996) found that a 13% accident reduction in urban areas was  generally associated with the introduction of speed cameras, a 10.9% reduction in accidents at rural speed camera sites and a 23% reduction in accidents at urban sites and casualty accident reduction of 8.9% during the first week after receipt of tickets from a speed camera operation.

In a presentation by Johan Joubert, an expert in motor vehicle accident reconstruction, he made mention of a study that had been undertaken in South Africa on Heidel-berg Road in Gauteng. Speed surveys were conducted at a known speed camera location. During the study the speed of 7000 vehicles was recorded.  The average speed of vehicles 500 m from the known speed enforcement location was 8 km/h higher than at the location itself.  This confirms that motorists slow down just before the known speed enforcement by camera locations but then increased speed again as soon as they have passed the location. 

(Read the rest of the article in SERVAMUS: July 2010)