Though I share the frustration of others at being stopped for no apparent reason at traffic signals when the roads are quiet, I cannot judge the Fleetsbridge scheme without the before-and-after statistics.

However, having been responsible for the first roundabout signals in Norwich in the late 1970s and for advising the Dept of Transport in the 1980s, I would like the opportunity to present my views.

Traffic signals at junctions and roundabouts inevitably add to delays in quiet periods and they cost money for highway works, equipment and maintenance, so a highway authority needs good justification to install them. Possible reasons for signalling a roundabout can be: a) There is a predominant flow from one direction so that traffic trying to join further round does not have a fair chance to get on the roundabout (city ring roads tend to be easier to navigate clockwise in the mornings and counter-clockwise in the evenings for this reason).

b) Fewer vehicle accidents – and less driver stress – by taking away the “shall I, shan’t I go?” dilemma that give-way lines present.

c) Other vehicle safety issues, for example where visibility is restricted or where drivers persistently go too fast for the conditions.

d) Improved safety for pedestrians and cyclists.

e) There is another junction close by, with limited queuing room between, as at the Tesco access at Fleetsbridge, where signals can provide co-ordination.

f) The junction is part of an area-wide computer co-ordinated signal scheme.

To switch signals off in quiet periods seems attractive but the necessary stop-lines and give-way markings on every approach can cause confusion and hence accidents.

I do not know to what extent these factors justify the Fleetsbridge signals but they may help to explain some of the issues that councils must consider.

Dr Tony Pawley, Cotton Close, Broadstone, Dorset