With Canberra so famous for its roundabouts it’s worth noting The Economist has a story on their history, and the social capital required to make them work:
The fate of roundabouts abroad thus repeats in miniature that of another British export, parliamentary democracy—another fine idea that backfires when mixed with jiggery-pokery. Just as democracy tends not to work without a free press, an independent judiciary and other helpful institutions, so roundabouts need decent drivers, straight police and reasonable infrastructure to function. The lesson of both is that fine ideas can wind up looking naive if they take no account of context and history. Swindon wasn’t built in a day.