Most commonly, carriers are covered up to $1,000,000 for liabilities such as lawsuits and other third-party insurance claims. Cargo insurance, on the other hand, will cover risks of loss or damage to the freight on the truck. If the carrier uses small trailers like a 1-4 open car carrier, coverage ranging from $175,000-$250,000 will be fine. When the carrier has larger trucks with 7-10 car open trailers, you should put their insurance under closer scrutiny.  We require any carrier we do business with to have at least $500,000 in cargo insurance for larger trucks because, in the event of a major claim, we need to make sure all freight is covered in full.  For an open 10 car carrier, that would cover $50,000 per car, which is more than the value of most cars on an open trailer.  For enclosed car carriers, which haul collectible cars and exotics, you will need to ensure that the carrier has even more insurance to cover their freight.
Cheap shipping quotes are usually a result of lower quality equipment and lower insurance, leading to lower insurance overheads. If you like to gamble with your assets, then shopping around for the cheapest option might be fun. However, if you value your car and peace of mind, make sure your carrier has sufficient coverage to ship your vehicle. Ask for a certificate of insurance when you get a quote to confirm you are working with a respectable outfit.