Skyway At-Grade operations are held jointly by the Skyway Operations and Maintenance Corporation (SOMCO) and SMC Skyway Corporation (formerly Citra Metro Manila Tollways Corporation), while the South Luzon Tollway segment of SLEX is held by SMC SLEX, Inc. (formerly South Luzon Tollway Corporation), a concessionaire operated by Manila Toll Expressway Systems, Inc. (MATES) and a joint venture of the Philippine National Construction Corporation and the San Miguel Corporation-backed PT Citra Marga Nusaphala Persada Tbk group of Indonesia. In addition, the Alabang Viaduct is also known as SLEX Toll Road 1 (TR1), while the section from Filinvest Exit to Calamba Exit in Calamba, Laguna is also known as SLEX Toll Road 2 (TR2) and the section from Calamba Exit to Santo Tomas Exit is also known as SLEX Toll Road 3 (TR3). The South Luzon Expressway continues the Osmeña Highway past the Magallanes Interchange, where it also meets Circumferential Road 4, particularly EDSA. The expressway runs through , spanning the cities of Makati, Pasay, Taguig, Parañaque, and Muntinlupa in Metro Manila and the provinces of Cavite, Laguna, and Batangas. From its northern terminus at Magallanes Interchange, the expressway follows a straight path southeast in parallel to the PNR South Main Line until the Bicutan Exit, where it slightly bends to the south towards the Alabang Exit. Two service roads run on either sides of the expressway from Sales Interchange to Alabang Exit, namely: West Service Road and East Service Road. At the Alabang Exit, South Luzon Expressway ascends to the Alabang Viaduct, a , eight-lane viaduct over the Manila South Road through Alabang. After its descent at Filinvest Exit, SLEX narrows to four lanes and mostly parallels the Manila South Road in Muntinlupa and northwestern Laguna, passing through the Susana Heights Exit connecting it to the Muntinlupa–Cavite Expressway. It continues as a straight roadway lined with billboards and passing through residential and industrial areas. Past the San Pedro Exit, the expressway then curves and ascends past the Petron and Caltex service areas. Past Santa Rosa Exit, South Luzon Expressway narrows into three lanes per direction, having guard rails as the median divider. At the Calamba Exit, the Pan-Philippine Highway concurrency ends as it leaves the expressway towards the west as Maharlika Highway. Past such exit, the expressway narrows to two lanes per direction, without exits and with bridges built with wide shoulders to accommodate future widening to three lanes. It follows