or, if you don't feel like waiting for your construction crews to get around to bulldozing the unwanted roadways, you can use this cheat if you have Tropico v1.0.2 (if you don't have the patch that promotes your copy to this version, go to http://www.talonsoft.com/patches/godgames/tropico.html
to get it):
1. press down the CTRL key, then type in the word RAPIDO. this turns on instant construction and demolition of buildings and other structures.
2. bulldoze away the offending roadway (or whatever else offends you for that matter).
3. press down the CTRL key and type in the word RAPIDO again to turn it off again....