Eoin Ó Catháin

Eoin Ó Catháin

Technical Director
TII & Dun Laoghaire Rathdown Co. Co.


Roughan & O’Donovan (ROD) based this upgrade scheme on a signalised roundabout solution that maximised throughput without causing queuing on the circulatory carriageway.


The first step in the development of our solution was the preparation of a traffic model, using S-Paramics software, to emulate the flows at the existing roundabout and to test upgrade options. The model was calibrated against on site observations.

We reviewed the balance of traffic flows at the junction and devised a signalised roundabout solution that solved existing congestion at the roundabout, with a buffer of spare capacity for an increase of up to 50% in traffic exiting from the M50, and made use of recently installed ducting.


Ensuring the continued efficient operation of the M50 mainline while upgrading the junction provided our key challenge.


The upgrade removed a significant immediate traffic hazard arising from underutilisation of capacity at the roundabout.

Services provided:

  • Civil engineering design
  • Traffic engineering

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