several 2 x 4's , turned up, should do the trick. Trucks come off
the concrete, roll over the 2 x 4 pieces, and THEN drop off, and not
break anything

you may want to stake them a bit at each end, so they will not be pushed
over.....


or, a 4 x 4 placed adjacent to the part of the driveway that the
trucks will drive off of, would do fine, but also try to stake it, so that
it doesn't push over.

some bricks of the proper size would do well too.

probably the easiest/ best bet is the wood pieces

hope this helps // let us know !!


james