Major deployment in sub-zero temperatures: How the winter service works on German highways

Winter service on German highways

• Ice and snow spoil the soup on more than 13,000 kilometers of freeway
• Instead of road salt, pre-wetted salt and increasingly brine are being used
• GTÜ warns: Be considerate of gritting vehicles and drive with foresight

Stuttgart. Germany is experiencing slippery roads and snowfall again these days. That’s when the road services are called into action. They are gritting and clearing to reduce the dangerous slipperiness. This applies from the main village road to the trunk road. The more than 13,000-kilometre-long freeway network, for which Autobahn GmbH has been responsible since 2017, plays a special role. Motor vehicles travel more than 235 billion kilometers a year on this high-performance infrastructure alone.

Slippery roads caused by freezing wetness or snow pose a considerable risk to road traffic, reminds the GTÜ Gesellschaft für Technische Überwachung mbH: Braking distances are significantly longer and there is a risk of skidding. This is evidenced by the higher accident figures at the onset of winter. The testing organization therefore urgently advises drivers to drive with particular foresight in appropriate weather conditions and to comply with the winter tyre requirement at all times. It is also particularly important to be considerate of gritting and clearing vehicles. After all, those who make the work of the experts against icy roads easier contribute to road safety in winter for everyone.

Whether on a municipal or state level – the deployment of road services to combat ice and snow is often a Herculean task. According to the federally owned organization, all ten branches of Autobahn GmbH with around 1,450 vehicles and around 6,300 employees are involved in winter road maintenance on the freeway network. However, the road maintenance staff are not only concerned with the issue when the temperature drops below zero. Preparations begin in midsummer, when salt stocks are replenished and the technology is checked. In the fall, the road maintenance professionals rebuild their heavy trucks and install gritting equipment, snow blades and sensors. Finally, from November 1, the winter service plan applies for Autobahn GmbH. The individual operations are then planned and carried out depending on the weather forecast and the results of measuring points and continuous test drives. Other road services operate in a similar way.

Combating winter with mechanics and chemistry

When you think of winter maintenance, you often think of heavy commercial vehicles in orange livery with a snow plough or snow blade at the front. This equipment is already needed when the snow is only a few centimetres high on the road. It is then mechanically pushed off the road. However, this is comparatively rare in Germany. Mountainous regions are an exception, especially the high alpine roads. More important for everyday winter driving in most regions of Germany is gritting to prevent icy roads. Today, salts are used almost exclusively for this purpose: primarily sodium chloride (table salt), but also calcium, magnesium and potassium chloride. They have a chemical effect, as a solution of water and salt has a lower freezing point than pure water, which is what ice and snow are made of.

Thanks to modern technology, salt can be spread extremely precisely and therefore economically. The corresponding development began back in the late 1930s with the invention of the spreader plate for dry salt granules. Today, technology for spreading pre-wetted salt is mostly used. Dampening salts are mixtures of salt granules and liquid brine in various mixing ratios. The abbreviation FS 30, for example, refers to a mixture of 70 percent salt granulate and 30 percent brine. Both components are carried on the vehicle in separate tanks and only mixed shortly before application.

Preventive treatment of road surfaces with pure brine (FS 100) has proven to be particularly effective against icy conditions. This salt solution is sprayed when forecasts and current weather data indicate dangerous road conditions. The brine bonds excellently with the road surface and only a small amount of salt is blown away by the wind. Autobahn GmbH is therefore testing innovative vehicles that are designed entirely for the economical use of brine in winter road maintenance instead of universal trucks with clearing and spreading equipment. This includes a battery-powered tractor unit with tanker and brine spraying system. The lower quantities of salt per kilometer of road benefit the environment, but also the infrastructure itself, as the road structure is less affected.

After the winter, drivers should remember to remove any road salt residue from their vehicle – at least by driving through a car wash or having their car professionally cleaned. This is because salt can promote the formation of rust on the bodywork in the long term – and even weaken components, which is relevant to safety. During the main inspection, the test engineers therefore pay close attention to critical rust spots.

Source and image: GTÜ, Editor: Michael Teschke.

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