The M1 is a major north–south motorway in England primarily connecting London to Leeds, where it joins the A1(M) near Aberford. While the M1 is considered to be the first inter-urban motorway to be completed in the United Kingdom, the first road to be built to motorway standard in the country was the Preston Bypass, which later became part of the M6. The motorway is long and was constructed in four phases. Most of the motorway was opened between 1959 and 1968 but the southern end was extended in 1977 and the northern end was extended in 1999. It forms part of the unsigned European route E13.