I dont know where to put this, but it's a recurring thing. I mean it's shown over and over and over again. People, animals, etc bowing to a Bodhi tree.
Here's a kinda similar pic. I have a feeling the structure is a small gate way to the building. You can see chariot/horses going though the same structure. Again
Very easy. Bullock carts have existed in the subcontinent sense the Indus civ and still exist in modern times. . . . . . Here's a nice cart.. Make it less ornate I guess and without that lion head. I like those openings on the cart above too. Looks like the railing design that pops up all the time in the reliefs.