Auto Insurance Claims: auto property damage, uninsured motorist coverage, company states

Question
I live in Florida. Stopped at a red light when the driver of a commercial vehicle lost control of his truck due to a medical emergency and hit 7 cars.  His insurance company states that I must file a claim under my own plan because the driver was underinsured. However,there were multiple collisions as the driver did not stop inbetween crashes.  Why is this considered a single accident.  Do I have to put claim in with my own company?  

Answer
This is considered a single loss.  It was triggered by one event, the semi losing control.

Assuming that you have uninsured motorist coverage, an underinsured motorist should be covered as well, depending on the limits that you elected to purchase.  In most states and with most insurers, UM claims should have no affect on your rates.  

This is what you pay premiums for.  File the claim and let your insurance company worry about the details.

Good luck!