Ringway 4 is deceptive and rather unique. For one thing, it's not actually a ring. It was first conceived in the 1940s by Abercrombie as a sedate "parkway" through open countryside around London, perhaps with a handful of grade-separated junctions at the busiest locations, but otherwise not really geared up for high-speed movement of heavy traffic loads. It was to be a "parkway" in the most literal sense: a pleasant tree-lined saunter through the home counties, designed and built as much for the pleasure of driving through the open country as for any practical purpose. For the parts that exist today, the reality is rather different. About 60 per cent of the route is part of the M25, and offers little in the way of pleasant country motoring.
In modifying Abercrombie's vision for the motorway mania of the 1960s, the Ministry of Transport created a plan that brings up yet more questions. The most glaring of these is: what was the purpose of Ringway 4? The question has to be asked because, in most of the documentation from the period in which the roads were planned, the job of allowing traffic with no business in London to get around the urban area was always assigned to Ringway 3. Why push long-distance traffic towards the second ring road in, especially when it actually runs through some urban areas? The page exploring the Ringway 3 plan in general suggests some possible answers.
Ringway 4 can also be considered rather odd because it's known that not all of it would be a motorway; in fact it seems that it was only rather late in the day that it was decided to route it largely along new roads to the north-west of London rather than use existing ones. The parts that are known to have been planned as motorways correspond to areas where Ringway 3 would have been in urban surroundings, so it's possible that it was intended to provide relief to sections of Ringway 3 that would be carrying a lot of local traffic. In the north, Ringway 3 was to run through open country and Ringway 4, some way distant from the urban mass of London, would be relegated to a dual carriageway A-road.
Despite all these uncertainties, Ringway 4 made it much nearer to being finished than other routes that seemed to have a solid purpose and a coherent plan. About two thirds of the route are open and in use today.
The following pages run anticlockwise from Navestock in Essex, because Ringway 4 does not have an eastern side.