First, this will take some work on your part, but it is critical for you to understand the concepts involved here.

First, your car was damaged, another person is 100% responsible for your loss. The other party is 'liable'.

So, what are your 'losses'? The cost to fix your car. PLUS the difference in value of your car the minute prior to the accident as compared to the same car with 15, 20,000 in damages and a damaged frame. (This is the DV) Plus the other costs to you: time, rentals, etc....document all this, at your hourly rate. (I will leave this out of the calc for now.)

Simply stated, you have suffered a loss due to the other driver and he is laible for that loss.

Lets say the repair is 18k. Lets say the DV is 7k. The other driver owes you $25k.

Now, stop for a moment. Notice something?

NOWHERE HAVE I SAID ONE WORD ABOUT INSURANCE.

The other guy owes you $25k, he says "sure. I have liability, they will pay that instead of me".

Here is a critical point: NO insurance "rule" or "procedure" or "thats how we do it" takes precedence over the laws that define liability.

Insurers are scum. Both YOUR company and the other will collude to screw you. Even though you WILL suffer a huge DV loss, YOUR insurer will refuse to help you out and will ignore your requests- they will claim your policy does not cover it (Collision does not); they will tell you "you are on your own", they will say "you need to ask the other insurer about that" (and the other insurer will refuse. They all collude against DV because there is nothing more hateful to them.

I will repeat: both insurers are your enemy.