The A10 ringroad surrounding the city connects Amsterdam with the Dutch national network of freeways. Interchanges on the A10 allow cars to enter the city by transferring to one of the 18 ''city roads'', numbered S101 through to S118. These city roads are regional roads without grade separation, and sometimes without a central reservation. Most are accessible by cyclists. The S100 ''Centrumring'' is a smaller ringroad circumnavigating the city's centre.