I’m doing first year of Industrial Design at uni, for the first semester I had to design a luggage trolley for airport use. This is what I made:
Front, top and side views:
metalogix.uw.hu/gallery/trolley_views.jpg
One of the most important thing in the trolley was to make it take up less space when not in use, either by folding it up, or packing more of them together, or any other way.
The way this one works is that the platform has two wings, that open up when another trolley is pushed into it from behind, see the next pic:
Note that this 3D representation was all done in ONE day, modelling, texturing, rendering in Blender (yuck, deadlines!!!).