Having trouble making tunnels

[crash1984]

I am somewhat new to SimCity4 and its mods. I have tried several different add-ons in order to create tunnels In smaller slopes. So far everyone I have tried has done the same thing. Taken the road over the slope and not through it. Does anyone have any ideas as to what may be causing them not to work and how I can fix it? I am using the Hole Digging Lots set to raise my terrain.