Reply to "Any suggestions on a better way of cutting curved roadbed?"

If you have access to a CNC router table that for sure is the best method.

Other wise use a trammel to lay out your fixed curved:  

Cut just out side the line with a Bosch jig saw then mounting the router on a trammel run the router directly on the line.  I use a 3/4" bit to just clean up the edge.,  If you use the router w/o the Bosch   jig sawto do the whole job the bit has a shorter life.

For the cosmetic curves somewhat the same

Blocks with lattice strips for cosmetic curves.  I use the lattice to project the lines, then cut just out side the lines,  then use the lattice to guide the router.............