Sir, – Tony Corcoran (Letters, August 3rd) calls upon St Christopher in his exasperation over signalling on roundabouts. I can think of more colourful invocations.Driving through a roundabout has become something of a lottery. While multi-lane roundabouts bring their own complexities, the basic conventions on most roundabouts are well established. Yet, judging by the signalling behaviour of some road users, one might conclude that they are either unknown or regarded as optional.The main rule is straightforward: signal left before leaving the roundabout, and signal left on approach if taking the first exit. Yet every day one encounters drivers signalling right when exiting, left when continuing around, or not signalling at all.One is left wondering whether hazard lights might be best, so that we are at least alerted to proceed with extra caution.Predictability is one of the foundations of road safety. A roundabout is intended to keep traffic flowing, not to become a test of patience and guesswork. – Yours, etc,PATRICK O’DONOGHUE,Maynooth, Co Kildare.