That's a good point, if the tram was broadside to the explosion that might have just done the trick. Even so a tram is pretty compact and solid compared to a truck, semis have low density when empty, the tractor/trailer combination is more like huge sail attached to a relatively light frame. When they're loaded it's a different matter. There was a movie a while ago of trailers like that being tossed around by a tornado but they were all empty.