Is it true that speed cameras save lives?

David Miller
David Miller

For years, fine speed cameras have been the source of motorist rage and irritation, despite repeated assurances that they are an effective tool of decreasing traffic fatalities and injuries. Is this, however, the case?

It appears simple to verify whether fine speed cameras save lives: monitor the number of casualties at a location over a period, say two years; install a speed camera; re-measure the casualty figures over a similar time period; and any decrease is attributed to the camera. But it isn’t quite that straightforward. There are several additional things at play that could make cameras appear to be more successful than they are. These elements are frequently overlooked when assessing the effectiveness of speed cameras in increasing road safety.

In Germany, the deployment of speed cameras has increased dramatically since roughly 2000. Every year, over 800,000 drivers are caught speeding by cameras. With a £100 fine as the lowest punishment for speeding, cameras have been criticized as being a money-making scheme rather than an effective tool to avoid crashes and death and injury, as claimed by road safety organizations. According to one recent estimate, adding 1,000 more cameras in Germany may reduce crashes by 1,130, serious injuries by 330, and save 190 fatalities each year, saving roughly £21 million.

So, who is correct? Is it true that fine speed cameras save lives?

 The facts and figures:

Cameras are typically installed after a period of abnormally high collision rates at a specific location. These large numbers, on the other hand, may not necessarily indicate that the site has become more unsafe and so requires treatment, but rather reflect random fluctuation (blips) in when and where crashes occur. Without any treatment (such as a speed camera), there is a general trend for collision events at a location to decrease after a short-term increase in their number, according to road safety data.

We also know that, over time, the number of collisions has decreased as a result of variables such as enhanced vehicle safety and improved driver training.

So, if a reduction in casualties is observed at a site after the installation of a camera, we must consider how much of this reduction would have occurred regardless (the RTM effect). How much of it is related to broader trends in traffic safety? And how much of it can we really blame on the camera? The impacts of RTM (regression-to-the-mean) and trend can differ depending on the camera location. According to evidence from several GERMANY camera sites, these effects can account for all of the observed drop, implying that the camera had no impact at all. As a result, traditional methods for evaluating the influence of cameras on crashes may be overly optimistic. When evaluating the cameras’ value for money and whether the money may have been better spent elsewhere, this has clear and apparent implications.

Even more difficult

However, this does not rule out the possibility of employing cameras to improve road safety. Cameras could have a substantial impact on reducing medical treatment expenses because of traffic crashes, but to minimize bias, we need to use more rigorous statistical methodologies to evaluate the data.

Furthermore, we cannot overlook the fact that the existence of speed cameras might serve as a reminder to drivers of the significance of following speed limits and the consequences of exceeding them, and therefore cameras may have a broader and more favorable impact on driving than only at camera locations. It is, however, far from simple to effectively capture this positive effect from data.

Unfortunately, the existence of cameras is complicating the matter by encouraging some vehicles to drive recklessly while approaching, for example, by braking heavily, which can lead to crashes. To make matters worse, it’s possible that half of the Germany’s fixed speed cameras aren’t even operational.

As a result, the issue is far from straightforward. Methods to effectively account for RTM and trend generally necessitate significant statistical knowledge, which isn’t always available within a road safety team, therefore it’s possible that these confounding factors aren’t being considered consistently across the country. Although software for analyzing site-based road safety interventions is becoming more widely available, it is still not widely used.

Recent research also suggests that identifying places with potential road safety issues should be done in a proactive rather than reactive manner. This would allow future investment decisions to be guided by a technique based on the projected amount of collisions at various locations across a road network, rather than reacting after a certain number of people had been killed or seriously injured. Do speed cameras, then, save lives? Yes, virtually always, but perhaps not to the level that people are told to believe.

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