You shrink a 10 foot by 5 foot by 10 foot carriage and all items contained within it into a model of the carriage, which fits in the palm of your hand, is a tiny object, and weighs 1 pound. If you are touching the model of the carriage and recast the spell, the vehicle regrows into a full sized vehicle after the spell is complete. The carriage has 15 AC and its hit point maximum is 25.
Your vehicle's actions are entirely dependent on your commands. In Combat, it rolls its own Initiative and acts on its own turn. Your carriage can move 30 feet on its turn, will not move into occupied spaces, and cannot make any other actions. If no commands are given, it will stay still, or move in the same direction issued on a previous turn. It can also be directed to follow roads or other pathways.
The carriage will store any nonmagical object placed within it, but any magical objects or creatures with 4 or more intelligence are ejected from the carriage when it is shrunken. Otherwise, anything it contains is shrunken with the carriage and remains inside of it.
At Higher Levels: When you cast this spell using a spell slot of 4th level or higher, the carriages hit point maximum and speed increase by 5 for each slot level above 3rd.
* - (an exquisite wooden carriage, 10 feet by 5 feet by 10 feet, constructed from rare materials worth at least 200 gp.)