The R21 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 the only other freeway (apart from the N1) that links 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 Hans Strijdom Road on-ramp in Monument Park, Pretoria, and the N12 in Boksburg, the R21 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 Eastern Pretoria Bypass near Centurion, the R24 near the airport, the N12 and N17 in Boksburg, and the N3 near Vosloorus on the East Rand, where it ends. The section from the N12 to the N3 is not a freeway. As early as the 1970s there were proposals to extend the R21 freeway further south and the freeway may be linked with the current eastern terminus of the M2 in Germiston in future.