It might be the most obviously unfinished motorway in the whole UK, let alone in London. The M23 was supposed to link London with Crawley - but its urban section was a problem that couldn't be solved.
Thousands of vehicles travel the M6 between the M56 and M62 each day. They all cross the River Mersey and the Manchester Ship Canal, and the bridge that carries them is notorious from travel reports nationwide. But what does it actually look like from the ground?