Case studies: the safety benefit of introducing speed limitsThere is clear evidence from sections on which a limit was introduced that the number of road deaths and injuries decreased. In December 2002 a 130 km/h limit was introduced on a 62km section of the Autobahn 24 between Berlin and Hamburg. This is the longest section on a German Autobahn on which a speed limit has been introduced in the past decade. The number of injury/material damage accidents decreased by 48% and the numbers of casualties decreased by 57% (comparing the 3 years before and 3 years after introduction).
In Rheinland-Pfalz, a 130 km speed limit was also introduced on a 167km section of the A61 in 1991 and has been retained since then. This measure was combined with a ban on overtaking for heavy good vehicles. The impact of these two measures was a 30% reduction in fatal and severe injury accidents (comparing one year after and one year before their introduction – Rheinland-Pfalz Ministry of Transport).
Finally, the Federal environment agency mentions further field trials that have shown reductions in road deaths and injuries: in one field trail in the Land of Hesse from November 1984 to May 1987, the speed was limited at 100km/h on some motorways, bringing down the number of accidents with deaths or injuries per billion vehicle kilometer by 25% to 50%. A field trial on the Autobahn A2 during 1992 and 1994 also showed a 50% decrease of the accident rate per billion vehicle kilometer (Umweltbundesamt, 1999).
The road safety impacts of speed limits were evaluated in 1984 by the Federal Highway Research Institute. The study estimated that a general limit of 120 km/h on the Autobahn network would lead to a 20% reduction of road deaths, a limit of 100 km/h even to a 37% reduction.
