Who's entering the signal that the runway is locked? What if they screw up?

There are so many failure modes with vehicles and planes using the same tarmac that I fail to see how anything would be worth developing here that doesn't eliminate that requirement altogether.

Currently it’s automated at this airport: https://www.faa.gov/air_traffic/technology/rwsl

Presumably this is lack of familiarity with this on the part of firefighters.