For a long time I have advocated developing a water soluble powder that could be added to water and lightly sprayed on road bed. When it dried it would form a non-soluble “paint” on the roadbed that would be invisible to the naked eye.
But when a helicopter flew overhead at night, and shined a particular light on the roadbed, they would be able to see if any part of the roadbed had been disturbed. A large black spot would show where an IED had been emplaced, even if the road bed had been patched.
Combat Engineers forever!!
And, that is a fantastic idea. Spray after clearing during the day, patrol overhead just before dawn. You should get a royalty for this.