Greenpeace Analysis with TomTom: Highway Construction Promotes Traffic Jams

As an evaluation by the NGO Greenpeace based on data from the navigation provider TomTom shows, the expansion of highways with additional lanes does not reduce the risk of congestion. In the vicinity of the highways, traffic jams even become more frequent after an expansion. The analysis compared car speeds on eight expansion routes in the year before construction and in the second year after the completion of the work. The analysis systematically demonstrates for the first time that the elimination of so-called bottlenecks on highways creates further bottlenecks.

"The data analysis debunks the myth of bottleneck elimination. Wider highways result in more traffic and even more congestion. This harms the climate and wastes taxpayers' money, which we urgently need for the expansion of climate-friendly railways. The federal government should concentrate all its planning capacities on this expansion," appeals Benjamin Gehrs, Greenpeace transport expert and author of the study.

In the ongoing coalition dispute over whether highways should be built more quickly in the future and thus with less stringent environmental regulations, bottleneck elimination has often been mentioned recently, according to the NGO. Consequently, highway sections that supposedly improve traffic flow are to be built quickly. The analysis, however, shows: While the average speed increased slightly overall after the expansion, it decreased in four out of eight cases for the slowest five percent of the recorded cars - a sign of increased congestion after the expansions. On surrounding main roads, there were more traffic disruptions in six out of eight cases.

The analysis examines the average speed of all recorded cars, the maximum speed of the slowest five percent, and the minimum speed of the fastest five percent. Accordingly, the biggest beneficiaries of an expansion are speeders outside of peak hours. In seven out of eight examined cases, the value for the fastest five percent increased above average. According to Greenpeace, the expansion of highways harms the climate in multiple ways: It generates additional traffic, more frequent congestion, and promotes high speeds outside of peak hours.

"This invalidates a frequently used argument for highway expansion: that CO₂ emissions could be reduced through additional lanes because traffic would soon flow more smoothly. The opposite is true: Because the expansion creates additional traffic, bottlenecks occur more frequently during peak hours both on and off the highway - rising CO₂ emissions are the result," concludes the NGO.