Like most US military installations, Fort Sill has its share of tracked vehicle traffic; more than most, since it's the location of the US Army's Field Artillery School. As such, there is an entire network of roads called Howitzer Trails dedicated just to them. So you see signs like this all over:

Howitzer Trail: Military Vehicles Only

There are lots of places where howitzer trails cross regular roads; the crossings all have stop signs on the howitzer trail sides, and signs like this on the road sides:

Howitzer Crossing

Whenever large vehicles like self-propelled howitzers or MLRS launchers are moving down these trails, they're required to have a road guard escort in a smaller vehicle, making sure it's safe to cross regular roads. Here's what happens when a MLRS launcher goes gallivanting around without an escort.