It prohibited to use studded winter tyres between April 16 – September 30, if winter road conditions do not apply or are expected. If winter road conditions apply you may use studded tyres, regardless of the date. However, you are never allowed to use studded tyres on streets where studded tyres are prohibited.
Winter road conditions apply when there is snow, ice, slush or frost on any part of the road. Keep in mind that the hard shoulder is also part of the road. In the event of a vehicle inspection, it is the police that determine whether wintry conditions apply at a particular location.