So if the vehicle continuously (or frequently, say every second) throws a cloud of dust forward, or sprays a mist of dark paint on everything ahead of it, including the bomb IR sensor, the thing would have to go off prematurely, right?I'm thinking street sweeper - kicking up a big cloud of dust from those dry, dust choked streets in Iraq ... enough to cover the sensor (a sensor NOT that much unlike IR motion detectors I'm assuming).
A street sweeper might not have enough reach, for the vehicle moves forward. Big leaf-blower might do, though. Or mount a long forward boom on a truck (say, at 8-9 feet height) and affix to it a sail-like opaque sheet of, say, metal, or dark plastic, or still better make that sheet a curtain made of smaller strips - so that the explosion would not destroy the whole thing and knock the boom out with its sail. The thing is to hang vertically, and to be edge-wise in the direction of the vehicle movement, so as not to obstruct the driver's vision field. But spray-painting would be better (with indelible paint) - that way one can tag those near the road who might have seen the bomb planted as well.