DAT is an abbreviation for Delivered at Terminal. This means that the seller is responsible for all transportation costs until the items are unloaded at the proper terminal. Furthermore, the seller must clear products for export (where applicable).
If the seller is unable to discharge the items at the agreed-upon terminal for whatever reason, he should consider shipping under DAP. The buyer will be responsible for any costs incurred after the unloading point. As with DAP, the vendor is liable for any delays or demurrage charges.