The Dft report LTN 1/09 SIgnal Controlled Roundabouts is useful section 4.4 some of which will be applicable to junctions also.

The link is http://www.dft.gov.uk/pgr/roads/tpm/ltnotes/ltn109roundabouts.pdf

The consclusion was that Part-time signals can result in potential safety problems, no provision for pedestrians and cyclists and a compromised layout

Largely as a result of this study there has been a move away from using part-time signals at roundabouts, and many formerly part-time signals have been converted to full-time operation. This is the case in Area 9.