Snow Chain Requirements

In Norway you need 7 chains, 1 for the front axle of the tractor, 4 across the drive & 2 for the trailer. If you are stopped without them you will be made to buy them at full price before you continue.
On winter tyres, you will officially need them on the unit & trailer. The frost mark is clearly visible on the tyre sidewall. In practice you’ll get away with the unit only (front & drive axle). But if you have an accident you could well find yourself in trouble if you don’t have them, I find the authorities are abit more lenient between Oslo & Svenesund, but if you venture into the country be prepared. They are good natured people but the way foreign trucks come to Norway unperpared for winter driving conditions annoys them.

On a separate point: DO NOT SPEED IN NORWAY. The fines will make you weep.