I have a loading dock that I need to make accessible to cars/trucks. I have thought about doing some kind of a ramp out of a trailer but it obviously has to be very sturdy. We do not want to fill in the dock because that was extremely expensive, but we do need to be able to get cars in the building this way. Any ideas?
Concrete.
Done. 
you would have to do a large steel plate with lots of bracing and diagonals and probably some HEAVY duty locking solid casters… it wouldnt be that hard to fab up if you had all the raw materials… would take about a day with a welder and a chop saw if you got some 4x8 sheets of plate steel and some steel square stock probably 1x3