A simple 2 wheeled cart. 2.7k trigs without subsurf. Could be optimized even more, there are many loop cuts to stabilize subsurf modifier. There is another the of cart on second layer. It alot higher in poly count than the original. Wheels and platform tilt is rigged and animated. Rendered in cycles with procedural materials. Mostly unwrapped as well.

Edit:
I have added a third cart which is larger and looks better.