Don B....If a UP car is on the BNSF, unless it's in some type of special service, the BNSF pays the UP a daily "car hire" rate depending on the type of car. Same goes for a BNSF car on the UP. The UP pays the car hire to BNSF until the car is returned to the home road. Demurrage is a charge paid by the customer, usually 12-24 hours after the car is spotted. these charges are accessed as an incentive for the customer to unload the car in a timely manner. These charges can vary depending on the type of car. Center beam flats and common box cars usually are about $65-$95 per car per day. So if a customer receives a 10 car spot and doesn't release the cars for say 36 hours, the customer would be charged $650.00-$950.00 in demurrage. And then there are switching fees but thats another story... Just another way for Railroads to collect a little extra money. Hope that helps...