The R21 / P157 is a major north–south provincial route (with a freeway portion designated as a National Road) in eastern Gauteng Province, South Africa. Built in the early 1970s, it remains one of two freeways (the other being the N1) linking Pretoria with Johannesburg, via the R24. As the eastern of the two freeways, it links the Pretoria city centre with OR Tambo International Airport, the N12 freeway, and Boksburg. Between the Solomon Mahlangu Drive on-ramp in Monument Park, Pretoria, and the N12 in Boksburg, the R21 / P157 is an 8 lane highway and motorway (freeway), with 4 lanes in each direction. It has off-ramps leading to Irene, Olifantsfontein, Benoni, and Kempton Park, including a partial offramp to Atlas Road. The route intersects the N1 Highway (Eastern Pretoria Bypass; Danie J