[asheshouse]

You need Full Mission Builder Plus to access the plate objects. Same to access things like airfield plates

Get it here:(The link is inoperative)
All you do is drop the FMB folder into your Mods folder. No txt edits to do.

You will see that the number of objects increases when you install this.
The order of the objects is as listed in static.ini, so the last ones are the road plates.

I can also access them if I switch to FMB Map Editing mode, but FMB+ is what you want for normal mission building use.

Ashe