In message , at 12:02:15 on Wed, 15 Feb
2017, Basil Jet remarked:
I'm amazed part-time lights at roundabouts are allowed. It seems
obvious to me that every time a blown red bulb faces traffic already on
the roundabout, you will have traffic joining the roundabout seeing a
green light and thinking it has the priority, and the traffic on the
roundabout seeing no light and thinking it has the priority.

There will usually (always?) be two red lights. And in any event, green
doesn't mean "full steam ahead", rather than "proceed with caution".
--
Roland Perry