Today we put the signals across each entry point, and time them in such a way that major flows around the junction get a green light as they pass around the roundabout itself. They are widely grumbled-about and undeniably controversial, especially when the lights are left on at quiet times, but done properly, it can be the solution to a junction's problems.
Something that sometimes goes hand-in-hand with signals, or can be used on its own, is the introduction of spiral markings. Spirals are designed to iron out lane-changing and make the best possible use of roadspace by allocating a path for every flow of traffic so that people cross over each other less often. The markings spiral out from the centre of the island and eventually deposit the motorist on their exit, and a properly spiralled roundabout should feel completely natural, leaving the motorist wondering why all roundabouts can't be so wonderful and calming.
Just like roundabout geometry, signalising and spiralising a roundabout can succeed or fail depending on the skill of the designer. There are good ones and bad ones; spirals that flow and spirals that seem to work against you. Very small roundabouts, in particular, are rarely suitable for these treatments. The junction of the A216 and A217 in Mitcham, South London (shown left), is a case in point: it's so small that the signals just let one arm of the junction go at once, and the spiral markings don't spiral, which means the junction never functions as a roundabout at all - just a circular obstacle to turning right.
Food, glorious food