In order to operate cost effectively, insurance companies use certain criteria top determine how extensively damaged a car is and whether it should never be returned to the road. With the huge diversity of cars on the road, the verdict can often be surprising. So how do the insurers decide whether your car is a write off when you make a claim?

Essentially, insurers use a complex matrix of factors to determine whether or not a car is a write off or can be fixed. This key point to note is that safety this cheapest option will always be triumphant.

Insurance companies will "write off" a vehicle when the cost of repairs is judged be more than the value of the car. This is a more complex calculation than it first appears because of the different costs involved with writing off a car.

1. Scrap value of the car can be a deciding factor

Let's look an example. If your vehicle is worth ?2500 and repairs cost ?1800 then surely you would expect to see your vehicle back on the road?

Not necessarily. Even the price of steal comes into play as the salvage value of the stripped car's carcass is factored into the equation. In this case, if your car is worth ?700 or more for scrap then the insurers will probably write the car off because although they will pay you ?2500 for the car they will be able to get back ?700 of that cost making it equivalent to the cost of repairs.

There are borderline cases to consider too ? looking at the example above, if your car were worth only ?400 in scrap the insurer may well decide to write off the car assuming that there is a high possibility that when repairs are started the mechanics may find further problems not revealed in the initial assessment, thus increasing the cost of repairs.

2. Parking charges

Many garages charge insurers extremely high rates for keeping "written off" vehicles on their premises. Insurers may wish to write off a vehicle quickly to avoid these kind of charges and then dispose of the vehicle at a salvage yard.

3. Type of policy

Another deciding factor in whether your vehicle is written off or not is the type of policy you have. For example, if you have a new for old policy the insurer may be more likely to write off the vehicle under the terms of your policy.

4. Hire charges

Again, the cost of car hire charges can effect the decision ? if your policy includes a courtesy car the charges for the hire of the car may prove too high for the insurers.