Big changes on the way for the M50

Variable speed limits on the way for the M50
Variable speed limits on the way for the M50

Variable speed limits will be introduced on the country's busiest road to improve traffic flows and reduce congestion.

Changes to access roads onto Dublin's M50, new signage to direct motorists to alternative routes in the event of lane closures caused by collisions, and new orbital bus routes will be used to reduce gridlock and reduce the risk of collisions.

The main measure involves introducing so-called variable speed limits, where the upper limit is reduced at peak times. This helps maintain average speeds across the length of the motorway, with less crossing and risk of collisions.

It comes amid growing concern about rising traffic volumes on the motorway, which caters for in excess of 350,000 vehicles a day.

Economic growth including a demand for goods and increased sales of new cars are resulting in congestion at key junctions, with volumes up 7pc so far this year. This follows a 5pc growth in 2014.

Transport Minister Paschal Donohoe has announced that over the next year, a number of measures are being enacted including improved merging layouts, which is currently being trialled on the N3 and M1 Airport junctions. This gives motorists more time to enter the motorway at junctions, and it is proposed to extend this to the N4, N7 and N81 junctions.

There will also be permanent signed diversion routes put in place, which will direct motorists to alternative routes on local roads. The diversions will be put in place in the event of collisions, and motorists will be advised of the changes through variable messaging systems across the motorway.

In addition, new orbital bus routes will be introduced from next year, including a new Route 175 between west Tallaght, Firhouse, Ballinteer, Dundrum and UCD.

This will serve significant demand between these areas and reduce the need to use private transport to access large retail, educational and employment destinations.

New routes will also be identified in North Dublin and between the M50 and the city centre next year, and some of the existing orbital routes will also operate at increased frequencies from 2017.

Variable speed limits will take up to three years to implement, and are expected to cost between €30m and €40m.

It involves adjusting the speed limits at certain parts of the motorway at busy times, for example in the morning and evening peaks. Motorists will be told in advance of the lower limits, which can be changed to suit traffic conditions, by way of variable message signs to be erected at overhead gantries. There will also be advance notice on approach roads.

The measure is likely to be used in combination with ramped-up enforcement, with cameras mounted on overhead gantries which would allow gardaí to prosecute drivers who break the lower limits.

Transport Infrastructure Ireland will use traffic data to determine what times the lower limits should be used, but they can be changed in real time.

The changes are designed to make maximum use of the available road space. Problems occur when motorists rely on the overtaking, or 'fast' lane, but then weave across up to four lanes of traffic to exit the motorway.

An even spread of vehicles using all available lanes, travelling at similar speeds, will result in better flows.