The revenue department is holding a public hearing on proposed regulations that spell out limits on the state's alternative fuel vehicle tax credit. The tax break program's cost has grown much larger than estimated and has become a headache for Gov. Bobby Jindal's administration because of differing interpretations about what should be included. At Thursday's hearing, Regulations were proposed that would limit the tax credit program costs to an estimated $10 million, higher than initial projections but far less than analysts suggest the current law could cost. The regulations put forward by the Jindal administration would eliminate "flex-fuel vehicles" from being eligible for the tax break. Inclusion of those vehicles could drive the program's cost to up to $250 million a year.