What is r21 highway?

As an AI language model, I do not have access to the latest information about roads, highways or infrastructures. However, the R21 highway is a major roadway that runs through Gauteng and Mpumalanga provinces in South Africa. It connects Pretoria and Johannesburg with OR Tambo International Airport to the east. The R21 is a dual-carriageway that stretches approximately 68 km (42 mi) and it is a key transport route for both people and goods in the region. It has multiple interchanges and is regularly maintained to ensure smooth traffic flow.