The Main Street Vehicles are my preschoolers must do each trip to the MK (no short rope drop lines for us).
They usually only run from opening until 10:15 a.m., and rides are supposed to be one way (though they are never busy) from Town Square to Cinderella Castle, and vice versa.
It seems to vary what vehicles they have out - we have ridden the trolley, jitney, old fashion fire engine and the double-decker omnibus.
The omnibus is the only vehicle that can take folded up strollers (the cast member will load it for you), and if you are in a vehicle while the Main Street Trolley Show is happening, then your vehicle will have to stop and wait.
The trolley and the omnibus usually have more people riding, but we have had the other vehicles to ourselves before. It's like your own personal parade down Main Street.