>Even in gridded streets roundabout are indeed useful.

At the risk of getting off the multipoint topic, we have lots of
roundabouts here in the UK. They very effectively and safely manage
low-to-medium traffic flows at intersections, although they tend to become
somewhat ineffective with extremely high traffic flows. In these cases,
they're usually traffic-light controlled, although a straightforward
US-style intersection would be just as effective if perhaps slightly less
safe (roundabouts reduce the incidences of high-speed 'broadsiding' which
appears to be an particular problem in North America).

The Dutch have similar-style roundabouts in places, although they're
usually single lane and located at quieter intersections. The French also
have 'roundabouts', although IMO theirs work less efficiently as it's the
cars on the roundabout that have to give way.

>I recall someone in LA mentioning California didn't have roundabouts for
>some legal reason: fear of crashes when people couldn't use them properly,
>and so the city didn't want the liability.

I vaguely recall seeing a roundabout somewhere in the San Diego area,
although they certainly don't seem to be commonplace.

Regards,

Kevin Meynell