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Do speed boundaries reduce the number of road deaths?
Once again the debate on whether German autobahns ought to have a speed limit has resurfaced. German Chancellor Angela Merkel’s challenger, Peer Steinbrueck has been attempting to halt a debate set off by a Social Democrat colleague about whether to introduce speed boundaries on all German highways.
The chairman of his party was quoted last Wednesday as telling that a seventy five mph (120 kph) autobahn limit would make sense because statistics suggest it would reduce serious accidents, according to Associated Press (AP).
Spreads of the motorway, most famously referenced by Top Gear, presently have no speed limit albeit the advisory limit stands at 81mph. The autobahn system, with a total length of 12,845km, has often been the topic of debate in the past and is a ensured catalyst for road safety groups, environmentalists and politicians.
But do speed boundaries affect the number of deaths on motorways? A two thousand eight report by the European Transport Safety Council (ETSC) found that of the six hundred forty five road deaths in Germany in 2006, 67% occurred on on motorway sections without thresholds and 33% on opens up with a permanent limit. The fact that 33% of German motorways have a permanent limit and 67% have either a improvised limit or none means that these figures, at very first glance, showcase that having a speed limit does not the lower the number of fatalities on motorways. But as ETSC note: ‘this similarity of percentages takes no account of traffic volumes on different sections.’
The report stresses however that:
“the relationship inbetween speed and road accidents has been studied extensively and is very clear: the higher the speed, the greater the probability of a crash and the severity of the crashes.”
The relationship inbetween speed and the increase in the number of deaths and injuries has lead to some interesting academic research. Writing about the ‘power model’ devised by Rune Elvik, from Norway’s Institute of Transport Economics, Peter Walker explains what insights it can suggest:
Using the most widely accepted statistical model, drawn up by a Norwegian academic using data from one hundred studies in more than a dozen countries, an increase in average traffic speeds of just 3mph – a typical switch for a 10mph rise – would be expected to cause more than twenty five extra deaths a year on motorways and more than one hundred serious injuries.
But of course, countries differ. Not only in their standard of driving but in the total lengths of motorway, average flows of vehicles, geographical situation (i.e many use Germany’s autobahns to cross over into other countries) and their overall transport infrastructure.
For many countries rural road fatalities account for the highest proportion of road deaths. Rural roads killed five times more people than motorways in Germany inbetween 2007-9, accounting for 60% for road deaths, versus 12% for motorways.
A one thousand nine hundred ninety one case investigate used in the ETSC report illustrates the results of introducing a speed limit. A 130km speed limit was introduced on a 167km section of the A61 in Rheinland-Pfalz combined with a ban on overtaking powerful good vehicles. The result of both these measures was a 30% reduction in fatal and severe injury accidents.
Professor Benjamin Heydecker, the Head of the Centre for Transport Studies at University College London also found that ‘during the forty five years since the current motorway speed limit of 70mph was very first implemented, the risk of road accident fatality per vehicle-km of travel has fallen to less than 1/13 of what it was’. But as Heydecker explains in his chunk for the London School of Economics (LSE), roads have become safer over that period of time due to a diversity of factors including road and vehicle development and not just the introduction of the speed limit.
In their two thousand eight report, the ETSC were rock-hard and clear in their overall conclusion:
empirical evidence indicates that all instances’ of introduced speed boundaries on German motorways have caused very large casualty reductions.
Do you think a speed limit should be introduced on Germany’s autobahns? What other factors could we look at? and is there another way to reduce motorway deaths? Comment in the thread below.
Data summary
Percentage share of road deaths per road type, 2007-2009 average
Click heading to sort table. Download this data
