Create simple vehicles such as sleds, sleighs, handcarts, and wagons

You would build a vehicle according to a 3D recipe similar to how you make golems, withers, and nether portals. You take the necessary blocks and place them in the world. Once you place the last required block, the vehicle gets summoned.

A sled would have two rails and can be pushed or pulled across land by a player. They would move really fast over snow and ice (as fast as you can run) and could carry one chest/furnace/etc or passenger. You would not be able to run at full speed.

A sleigh would be the same thing as a sled but could be pulled by one horse, donkey, or mule that has a saddle on it. You right-click attach a bridle (new item) to the sleigh and then right-click attach the bridle to the animal to combine them. Now you can mount the sleigh as a passenger, or mount the animal to control it, or put a chest/furnace/etc in it for storage.

Handcarts would be similar to sleds, and wagons similar to sleighs, but these should move fastest through warm and temperate biomes. I don't see any issue with adding "wheeled" vehicles, because the game has rails and minecarts, all of which imply the existence of the wheel already.