M4 motorway not signed, European route E30 includes most of the M4. The M4 has two sections of smart motorway. The one between junctions 19 (M32) and 20 (M5) north of Bristol has variable speed limits and a part-time hard-shoulder. Completion was in summer 2014. The section between junctions 24 and 29 in Newport has variable speed limits. In 2010 it was announced that a smart motorway would be constructed between junctions 3 and 12, with work starting in Autumn 2018. This will be the longest smart motorway scheme in the United Kingdom, with a length of 51km (32 miles). Work is
Leica M4 without a viewfinder was made as Leica MDa (similar to the Leica M1). Production of the M4 stopped briefly in 1972. Its successor, the M5 had been introduced in 1971. However, the relatively bulky and expensive M5 met with a cool reception, and sales did not live up to Leica's expectations. Production of the M4 was therefore restarted quickly until 1975. In the year 1975, a special edition was made for Leica's 50th Anniversary, and in 1977 the company launched the updated M4-2, which was based on the M4's body, but with a streamlined production process that reduced manufacturing cost.