In Norway, the vehicle owner must provide the minimum of liability insurance for his/her vehicle(s) – of any kind. Otherwise, the vehicle is illegal to use. If a person drives a vehicle belonging to someone else, and has an accident, the insurance will cover for damage done. Note that the policy carrier can choose to limit the coverage to only apply for family members or person over a certain age.
The use of non-intrusive load monitoring to detect drunk driving and other risky behaviors has been proposed. A US patent application combining this technology with a usage based insurance product to create a new type of behavior based auto insurance product is currently open for public comment on peer to patent. See Behavior-based safety. Behaviour based Insurance focusing upon driving is often called Telematics or Telematics2.0 in some cases monitoring focus upon behavioural analysis such as smooth driving.
Liability insurance pays for damage to someone else’s property or for injury to other persons resulting from an accident for which the insured is judged legally liable; collision insurance pays for damage to the insured car if it collides with another vehicle or object; comprehensive insurance pays for damage to the insured car resulting from fire or theft or many other causes; medical-payment insurance covers medical treatment for the policyholder and his passengers.
If the younger driver is covering his own costs, it might be cheaper for him to take out his own policy but include one of the older, lower risk drivers from the household as a named driver (as long as the older drive will use the car). However, if the older driver is footing the bill for both policies, multi-car insurance may still work out cheaper.
You’ll notice that none of that liability coverage pays for your car or injuries, nor for any injuries your passengers sustain if you cause a wreck. This is why many people — particularly those whose car isn’t yet paid off — want “full coverage” car insurance. This isn’t actually a type of coverage, but instead typically refers to policies that include liability coverage, plus comprehensive and collision coverages.