I suppose spray trains are no longer used but I've seen hi-rail spray trucks (may be contractors) and heard of using steam jets to kill younger weeds. (steam dissolves the waxy coating found on leaves causing plant to dry out and die). All of these are probably higher-cost approaches. Streetcar systems used to employ gas-powered weed burners.

You might see if a local university might have some suggestions on how best to proceed. For example, the timing of any "mechanical" treatment may be important to kill or disturb a plant before it produces seeds for next year.