The insurance necessary for intermodal haulers is much the same as for any other trucker.  For complete protection you need coverage for:

•  Liability, bodily injury — covers you for injuries to other persons for which you are held responsible.* Property damage — covers you for damage to other persons’ property for which you are held responsible.
• Medical payments (medpay) — covers your and your passengers’ medical payments for injuries suffered while you are driving your truck.
• Collision — covers your truck and trailer for collision with another vehicle or stationary object and for rollovers.
• Trailer interchange agreement with at least $1 million in coverage.
• Non-trucking liability coverage; recommended minimum of $1 million; this covers you if you do any personal business while on a road trip (see separate article on this coverage)
• Cargo – covers the cargo you are hauling (see separate article on cargo insurance).
• Comprehensive — covers your truck and trailer for fire, theft, vandalism.
• Loading & unloading — covers cargo during loading & unloading.
• Towing & storage — covers towing & storage for truck, trailer, and equipment that has been damaged.
• Debris removal — covers costs of removing debris after a collision, rollover, or cargo-spill.
• Pollution — covers damage caused by release of pollutants.
• Earned freight — covers you if you arrive at the delivery point with the goods but are not paid, or are only partially paid, for the delivery due to damage to the cargo; earned freight coverage allows you to recover the freight charges from your insurer (instead of the shipper).
• Loss mitigation (aka sue & labor) — covers costs you incur to prevent further damage to cargo after a collision, rollover, or other incident.
• Downtime — covers you for up to $100 per day for up to 30 days if you are unable to work due to damage to your truck.
• Loan/lease/gap — if you make a small downpayment and have a long-term loan and then, shortly after you buy your truck, it is stolen or totaled, you will likely owe more on the loan than the truck is worth, and thus the payment you receive from your insurer for the loss of the truck will be less than what you owe.  Loan/lease/gap insurance covers you for the difference.