Car hire companies are lining their deep pockets with a 'winterisation' charge at many European ski destinations this winter.

The charge, which includes the price of winter tyres and/or snow chains and can normally only be purchased at the rental desk, varies markedly across Europe as well as from rental company to rental company.

The average 'winterisation' fee across six destinations researched (i.e., Geneva, Grenoble, Innsbruck, Barcelona, Turin and Sophia in Bulgaria) was £35, but travellers could pay as much as £110 with Europcar, Enterprise and Sixt in Geneva, falling to a more reasonable £53 if hiring from Hertz in Barcelona and down to £24 in Sofia, hiring from Avis.

The research by iCarhireinsurance.com, surveyed the car hire costs charged by six rental companies, Avis, Budget, Enterprise, Europcar, Sixt and Hertz, in six ski destinations for a week's car hire from 27 December 2017 to 3 January 2018.

Turin aside, the ‘winterisation’ charge is optional in all the destinations. Travellers in Turin should expect to pay a compulsory fee of £38 with Hertz, and £40 with Enterprise, for example.

However, it is the responsibility of the driver and not the rental company to ensure that the hire car is suitably equipped for the wintery conditions they are driving in. This can be a challenge when the rules on winter tyres and snow chains differ from country to country.

In Austria, for instance, driving without winter tyres between the start of November and mid-April can lead to a fine of around €5,000 (£4,430), coupled with the risk of the car being impounded. Despite all of this, Sixt charges an additional £32 for winter tyres and snow chains at Innsbruck.

In Germany, winter tyres are mandatory in wintery conditions, whilst in Switzerland, Bulgaria, Italy and Andorra they are just ‘recommended’. However, vehicles which are not equipped to travel through snow, potentially impeding traffic, may be fined. In France, winter tyres are not mandatory but in snowy conditions special signs may indicate they should be in use.

Ernesto Suarez, CEO and founder of iCarhireinsurance.com, says: When you’re driving a hire car it’s your responsibility that the car adheres to the local laws and regulations as it’s you that’ll be fined if it’s not properly equipped for wintery conditions and not the hire car company. In the Alps, for instance, it’s commonplace to see police roadblocks on the approach to ski resorts and the police may well refuse entry to a car, for instance, without chains if it's a designated 'snow chain' area. The driver may also have to pay a fine.

iCarhireinsurance has produced a winter driving infographic giving tips on winter driving and details of the rules in different European countries.