The final section of the M1 was opened to Junction 1 at Staples Corner in 1977. There the motorway meets the North Circular Road (A406) at a grade separated junction and roundabout. Unrealised plans from the 1960s would have seen the motorway continue through the junction on an elevated roadway to end at West Hampstead, where it would have met the North Cross Route, the northern section of the London Motorway Box, a proposed ring of urban motorway around the central area. The layout of the Staples Corner junction was originally built in accordance with those plans, although most of the London Ringways Plan had been cancelled by 1973. Around the same time, the section between the then-M10 and Junction 5 was widened from the original two lanes to three.