How much does each laser system cost though, plus maintenance?
Also, the sign can just be ignored by the driver & the bridge still hit. Once the I beam is perpendicular to the road, it shouldn't roll the truck onto the other side of the road either. Or slant the I beam off to the kerb side to prevent it. Either way, stops the bridge being hit, where the truck could roll into oncoming traffic anyway - as was almost the case in the Amiens St pic above. It is far easier to replace an I beam than to have to inspect/repair the bridge, let alone the nasty accident that could occur if the rail gauge was damaged by the strike.