[0xffff2]

Yes, I get that. But an airport is not a rail network. The question is how you would actually implement physical interlocks on an airport in a way that works and is safe while controlling movement of everything from a pickup truck to an A380? It's an incredibly hard problem to solve. And keeping in mind too that the Runway Status/Entrance Lights first started development over 30 years ago and are still only deployed at 20 airports, despite being a vastly simpler system than one controlling physical barriers.

[BobaFloutist]

I'm curious how much of a buffer there is between the time the sensors detect the airplane and it being safe to enter the runway.

Is it definitely safe to cross the runway in a vehicle moving a normal speed up to the moment before the lights turn red? Is it safe for a little bit afterward? Or is it unsafe even a little before the lights turn red?