Originally planned as a new-build route across South London, construction of the first section of the South Circular near Eltham began in 1921 to a high-quality specification. The remainder of the road was supposed to be of a similar standard but it was repeatedly delayed, and the current route was allocated in the late 1930s to existing urban streets instead. Despite several proposals to either upgrade the road or replace it with a parallel motorway, there has been little change in the century since the route was first planned and most of the road is still urban streets. The South Circular has received sustained criticism for congestion and pollution and is one of the least popular roads in Britain.