A studded tyre during winter is a safe bet as long as you drive with them during the time period they are allowed. Most areas will have some restrictions of the time period of when you can earliest mount them on your car and the date when they have to be removed. This also means that you can mount them as soon as you are allowed, to ensure that you are ready for the upcoming winter.
Studded tyres have protruding studs, which are embedded into the tread of the tyre. The studded tyres will give you the best grip on ice and hard packed snow. They will give you the necessary traction when you start accelerating and when you brake. Also when you take corners, they will prevent you from gliding sideways. During the time you have them mounted on your car, you will have the best and safest option for driving in winter conditions. You can safely drive with them until the tread depth goes below 4mm. When it does it is time to buy a new set. To make sure that the wear is even, you should rotate the positions of the tyres between the yearly changes.