[How to use Pioneer bridge ramps on SPW 251/7?]

thanks for your answers.   Is there any other way for tanks or other vehicles to make use of the fords on the right and left flanks to cross the Rzadza river in this first mission of "Blunting the Spear?"  

[How to use Pioneer bridge ramps on SPW 251/7?]

I am playing the first mission of "Blunting the Spear," and I have two SPW 251/7 fitted with "assault bridge ramps."   Can anyone tell me how to use these ramps to facilitate vehicles crossing one of the fords across the Rzadza River?   I'm not seeing a special command for either the SPW 251/7s or the Pioneer units riding in them.  And when I try a waypoint over one of the fords, I get a red marker making it clear that the unit cannot enter the ford.