BART, like other transit systems of the same era, endeavored to connect outlying suburbs with job centers in Oakland and San Francisco by building lines that paralleled established commuting routes of the region's freeway system. The majority of BART's service area, as measured by percentage of system length, consists of low-density suburbs. Unlike the Chicago "L" or the London Underground, individual BART lines do not provide frequent local service. Within San Francisco city limits, Muni provides local light rail surface and subway service, and runs with smaller headways (and therefore provides more frequent service) than BART.