Orbital routes (such as the proposed circular roads) don't work well in practice because slight delays tend to propagate easily and quickly all the way around t

Orbital routes (such as the proposed circular roads) don't work well in practice because slight delays tend to propagate easily and quickly all the way around the circle, with no recovery time at either end of the route (because there is no end). This is why the Circle line of the London Underground was changed a few years ago into a spiral shape, and why the M25 motorway gets congested so easily. A better configuration would be three spiral shapes, giving the route defined start- and end-points to allow recovery time for delays.