Sir, – Shane O’Doherty (Letters, April 4th) asks “would it be possible to measure the impact of suspending scarcely used bus lanes for a few months and allowing rush hour traffic the full road space to flow more quickly“? This is a misunderstanding of the purpose of bus lanes and the workings of traffic flow.
Traffic jams are all ultimately caused by conflicts in traffic flows – for instance, at junctions and roundabouts (and occasionally by accidents along roads). Tailbacks are caused by a traffic conflict ahead, and a lack of capacity at the point of conflict. The purpose of bus lanes is to change the priority of vehicles in reaching the points of conflict – giving a peak bus with 80 passengers priority over a car with an average of perhaps two occupants.
Suspending the operation of bus lanes would do nothing to improve overall traffic flows, as these are governed by the flows across and around junctions and roundabouts. The justification for the provision of bus lanes is that it minimises the average journey time for road users as a whole. Yours, etc,
TIM WILSON,
Watson Park,
Killiney,
Co Dublin
Sir, – I have to point out the folly of Shane O’Doherty’s suggestion (Letters, April 4th ) that bus lanes be opened up to cars at rush hour. The choke points on Dublin’s traffic system are not on the “empty” lengths of bus lane but at the many junctions on its radial routes and the bridges across the rivers and canals, where there is often no bus lane.
All Mr O’Doherty’s suggestion would do is move the queue nearer the junction – it would in no way hasten deliveries, workers or shoppers through the junction. However, it would have a devastating effect on the service speed of bus journeys and the safety of pedal cycle journeys and send many of those users to their own cars, which would in turn further congest the choke points and in the process delay Mr O’Doherty and everyone else even more. Based on Dublin City Council’s annual cordon counts, we must note that cars are 80 per cent of the traffic but carry less than 40 per cent of the passengers. However, I will commend the car for one thing: it is the most efficient system in the world for moving empty seats, as cars are typically 75 per cent empty. Yours, etc,
COLM MOORE,
Kenilworth Square,
Dublin 6