Qu’est-ce qu’une barrière de dégel ?

What is a thaw barrier?

The thaw barrier is a road restriction that prohibits heavyweight exceeding a certain weight to travel on certain lanes. It is put in place after a period of frost to preserve the roadway.

When it freezes, the water in the ground turns into ice and causes road networks to swell. During the thaw period, the water returns to a liquid state. It begins by liquefying in the upper layers of the soil, and the water is then trapped between the upper layers and the still frozen lower layers.

The bearing capacity of the roadway is reduced and it is therefore dangerous for trucks to travel on it. A thawing barrier is then put in place to ban heavy goods vehicle traffic while the excess water accumulated in the roadway drains away.

If the presence of a thaw barrier is essential for the safety of truck drivers and the preservation of roads , it nevertheless represents a major constraint for the logistics sector which sees its goods transport activity compromised until further notice.


The installation of a thaw barrier at the end of a period of extreme cold is not systematic. It is only applied to certain roads , depending on their vulnerability to the phenomenon. This is assessed by measuring their deflection , in other words their degree of inflation/deflation. Each road is evaluated individually to estimate whether it is necessary to install a thaw barrier at its entrance or not.

In the majority of cases, major roads remain open to heavy goods vehicles, except during the most intense periods of frost.

The decision to install a thawing barrier is taken in the form of an order from the prefect, the president of the departmental council or the mayor depending on the nature of the road.


The thaw barrier is placed at least 18 hours before the restriction takes effect . It becomes so at 8 a.m. , after the information has been widely disseminated in local media and information sources intended for truck drivers. It is usually removed a few days later , provided that measurements reveal that the excess water is sufficiently drained. To find out, new tests are being carried out on the roads concerned.


There tonnage limitation imposed by the thaw barrier depends on the specific decree which governs it. In certain cases, only heavy goods vehicles whose GVW (total authorized weight) exceeds 12 tonnes and which transport goods whose weight is greater than 50% of the vehicle's payload are concerned. In others, the thawing barrier applies to heavy goods vehicles with a GVWR of 7.5 tonnes or 3.5 tonnes, depending on the level of fragility of the roadway.

However, certain vehicles which fall into this category may be authorized to circulate by exemption . This is particularly the case for fire trucks, household waste trucks, recovery vehicles, funeral transport vehicles, vehicles transporting blood products and human organs, etc.


In the event of an inspection, any person traveling on the route marked by a thaw barrier without exemption must be able to justify the urgent nature of their trip and the impossibility of taking an alternative route . An infringement of the regulatory provisions concerning thawing barriers exposes the offender to a fine of €1,500 , or even €3,000 and three years of driving license suspension in the event of a recurrence.


Although they are necessary for the operation of road infrastructure and essential to the safety of those who use them, thawing barriers can be very disabling when they prevent users from going where they are expected.

There is no solution to ignore this regulation. The best attitude to adopt to deal with thawing barriers and prevent them from disrupting your work is to keep informed of weather forecasts , anticipate the end of a prolonged period of low temperatures and stay on the lookout for sources of information competent to make the necessary arrangements. You will thus be able to adapt your itinerary according to blocked roads and plan, if necessary, a greater range of times. to compensate.

When they are not subject to a thawing barrier, the roads are sometimes regulated by the Mountain law or the B26 sign which requires their users to equip their vehicles with special anti-slip equipment . While snow chains and winter tires are expensive and complicated to install and snow socks are too fragile, it is advisable to equip yourself with a device that is both reliable and practical: anti-slip over-tyres .

Musher premium anti-slip over-tyres are designed to allow you to drive in complete compliance and safety on snowy and icy roads, but also on dry asphalt. They are mounted on the wheels in less than 5 minutes and adapt to any type of vehicle. No more roads will close its doors to you!