Looking for new travel savings? Companies with mature travel programs have generally done well at managing savings on major spend categories: air, hotel, car rental in the U.S., and rail in Europe. In this paper, author Claudia Unger looks at several other sub-categories of travel spend that are considerably more hidden. These include dining and entertainment, ground transportation and mobile charges. Because travelers buy these services outside of the boundaries of the travel program, data on this spend can be hard to come by.