In addition to the extensive highway system, the cities and regions within San Diego–Tijuana are interconnected by many state routes as well. State Route 52 connects communities in northern San Diego, State Route 905 connects the Otay Mesa Port of Entry with South Bay cities, State Route 125 connects South Bay with East County, State Route 94 connects South Bay with the Mountain Empire, and State Route 78 connects North County Coastal with North County Inland, as well as to the mountain communities of the San Diego County Peninsular Ranges.