VE-I-4: Weather-related road traffic accidents

The picture shows a close-up of a roadway covered with water. A car is almost hitting another car.Click to enlarge
Heavy rain increases aquaplaning hazards thus increasing accident risks.
Source: Photograph: © chokchaipoo /

2019 Monitoring Report on the German Strategy for Adaptation to Climate Change

Table of Contents


VE-I-4: Weather-related road traffic accidents

In 2010, very wintery road conditions both in January and February but also in December, were the cause of an unusually high number of accidents as a result of slippery conditions on roads covered in snow and black ice. Roads made slippery by rain as a contributory factor in accidents have shown a significant decline. Regarding the other time
series, no significant trends have been observed so far.

The graph shows the percentage of weather-related road accidents with personal injury from 1998 to 2017. The accidents from June to August are shown in a column chart.
VE-I-4: Weather-related road traffic accidents

The graph shows the percentage of weather-related road accidents with personal injury from 1998 to 2017. The accidents from June to August are shown in a column chart. The values are in the range of 30 percent. There is no trend. In addition, two lines show the contributory cause of slippery roads due to snow and ice as well as slippery roads due to rain. There is no trend for the contributory cause of icy roads and snow, but there is a decreasing trend for the contributory cause of icy roads and rain.

Source: StBA (statistics of road traffic accidents)

Travelling safely, come snow or ice, rain or heat

Road safety and accidents on Germany’s roads depend on numerous factors of influence. Apart from the existing infrastructure as well as the density and structure of traffic and the behaviour of road users, these also include the weather and prevailing weather patterns. Rain and snow, as well as ice and hailstones impact on roads, making for adverse driving conditions such as aquaplaning or slippery roads, pavements and cycle lanes. Precipitation and fog reduce visibility. The risk of accidents is therefore usually greater in the autumn and winter months than in spring and summer. Overall, there are more accidents in those months. However, as road users tend to adjust their speeds to hazardous conditions, there are fewer accidents causing personal injury during that time than in the warmer months. This situation is furthermore influenced by the choice of one’s mode of transport: Humans prefer travelling by car or public transport. The latter reduces the number of unprotected and particularly vulnerable road users being exposed to road traffic.

During the warm season, it is possible to observe contrary behavioural patterns. People make use of pleasant temperatures and longer days. They move about more in public spaces and do more errands on foot or by means of a bicycle or two-wheeled power-driven vehicle. The motoring environment is becoming generally more complex while the proportion of weaker road users is increasing. Moreover, in good, dry weather road users with power-driven vehicles tend to drive faster than in slippery or wet road conditions, thus provoking more serious accidents. Although over the summer months the number of accidents – compared to the year as a whole – is average, the proportion of accidents where people are injured or killed, is particularly high at that time of year.

According to an evaluation carried out by the Federal Bureau of Statistics (Statistische Bundesamt), the accident situation exemplifies60 – in what way the weather and prevailing weather conditions can influence road safety. During the months of January, February and December, the prevailing road conditions tended to be very wintery. Snow and black ice were joint causes of almost twice as many accidents involving personal injury as in other years during the period in question. Nevertheless the relative proportion of accidents involving personal injury was in those months at its lowest level since 1991. Overall, the number of accidents was much higher, but thanks to basically more cautious driving, the accidents involved only material damage. By contrast, the proportion of accidents involving personal injury was above-average high in the summer months of 2010 and 2013. As far as 2010 is concerned part of the blame can be apportioned to the weather, because June and July of that year were generally very sunny and, more importantly, hot. Compared to the past ten years, in 2013 there were overall fewer accidents involving personal injury. The relatively hot July of 2013 was, in fact, the most accident-prone month of the entire period examined and it accounts for the high proportion of accidents in the summer months of that year.

In view of the influence which weather and prevailing weather patterns can have on accidents happening, it is currently under discussion whether climate change might have relevant impacts on road safety and the incidence of accidents. In this context, wintery hazards are expected to diminish in future whereas in spring, summer and autumn it is expected that greater heat and increased heavy rainfall might contribute to increasing the frequency of accidents. In some regions dust and sandstorms contributed to accidents in recent years. As the intensity of soil desiccation increases, such storms might occur more often in future. So far, no significant trends have been observed in the time series illustrated for road accidents involving snow and black ice as contributing factors, or indeed for road accidents in the summer months. However, accidents involving slippery roads in rainy weather as contributing factor show a significant falling trend since 1998.

It is up to road users to inform themselves of prevailing hazards, to take note of warnings and to behave correctly and appropriately in extreme situations. On the other hand, they do rely, in principle, on transport infrastructures functioning even under extreme conditions and that no damage is caused by prevailing weather patterns. It is part of the remit of the Federal and Länder governments, to adapt transport infrastructures to changing climatic conditions. In order to lay the appropriate foundations, a research programme was initiated by the Federal Highway Institute (Bundesanstalt für Straßenwesen). This programme is entitled ‘Adaptation of road transport infrastructure to climate change’ (AdSVIS/Adaptation der Straßenverkehrsinfrastruktur an den Klimawandel)61. For example, in this light a project was carried out under the title ‘RIVA – risk analysis of important transport routes in the federal trunk road network with regard to climate change’ (Risikoanalyse wichtiger Verkehrsachsen des Bundesfernstraßennetzes im Kontext des Klimawandels). The purpose of this project was to develop a methodology which would make it easier to assess climatic risks facing the federal trunk road network. Other research projects address e.g. the development of appropriate indicators for the RIVA tool, for instance on the subject of heat, involving the mapping of potential flood areas or regarding the resilience of the road transport infrastructure.

60 StBA –Statistisches Bundesamt (Hrsg.) 2011: Unfallentwicklung auf deutschen Straßen 2010. Begleitmaterial zur Pressekonferenz am 6. Juli 2011 in Berlin. Wiesbaden, 38 pp.
61 Laufzeit: Januar 2011 bis Dezember 2014



GE-I-1: Heat exposure and awareness

VE-I-3: Heavy rain and roads

VE-I-5: Impacts on roads from extraordinary weather events and disasters - case study





Monitoring the contrary impacts of possibly decreasing accident risks in winter and possibly increasing accident risks in summer (DAS, ch. 3.2.11)

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 Adaptation on climate change  KomPass  Monitoring Report 2019