Time for measures to get drivers to slow down on the Porterstown Road, council says

Just west of the M50 and Castleknock, the Porterstown Road looks like a rural road.

Its footpaths are slim, and flanked by trees, and neighboured by the vast lawns of the Castleknock Golf Club.

There are moments of calm. But, every now and then, a car or van barrels down the road at mighty speeds.

Eimear Carbone-Mangan, a local Fianna Fáil councillor, sometimes runs along that road, she said on Monday. “And it is appalling.”

Ten years ago it was a rural road, but a lot has changed, says Fine Gael Councillor Ted Leddy. “Now, it’s very much an urban road.”

That change was brought by a spate of new developments in the area, he says. Like, the Diswellstown Manor housing estate, new clubhouse at the Castleknock GAA club, and council upgrades to Porterstown Park.

The local Castleknock Hotel also got an upgrade, Leddy said on Tuesday morning. “That has all significantly changed the amount of activity, pedestrian and otherwise.”

For a good while now, the issue of safety on the Porterstown Road had been coming up in council discussions, he says. “But it really crystallised during the summer when there was an accident involving a young boy.”

Two children were injured on the road in April and June 2024, adding to the five car collisions recorded there over the last five years, according to a petition launched by local campaigners on 18 June.

To try to make the Porterstown Road a less dangerous route, the council is now looking to lower the speed limit and – eventually, maybe, install speed ramps.

Diagnosing the problem

At the September meeting of the area committee, Fine Gael Councillor Siobhan Shovlin had tabled a motion asking the council to reduce the speed limit from 60km/h to 50km/h on Porterstown Road.

But a few signs advertising a lower speed wasn’t going to do it, Labour Councillor John Walsh said at the same meeting, as he tabled his own motion. “Whatever route we take to get there, ramps are absolutely going to be needed on this road.”

Council officials’ first step has been to do speed surveys.

At the area meeting on 28 November, Quintin Greally, an executive engineer, said they had set up 12 automatic traffic counters across the road.

Average traffic speeds along the road varied between 42.6km/h and 57.4km/h, said Greally.

But at the three specific points, the average speed at which 15 percent of motorists were travelling was above the existing 60km/h speed limit.

Greally said he wouldn’t expect that just dropping the speed limit down to 50km/h in some spots would be effective without adding physical traffic-calming measures, he said.

But if they do vote to cut the limit, there would need to be a “bedding-in” period of two or three months to see how the new limit fares before they look at ramps, he said, with more surveys needed after that.

Reductions and ramps

To change a speed limit, the council would need to put the idea out for public consultation in January and then put the proposal to the full council for a vote in April or May, said Greally.

Then they would aspire to do more speed surveys in September 2025, he said. “Based on that data then, we will have a very good idea if more traffic-calming measures are required.”

Ramps may be put in places where motorists currently drive faster than 60km/h, Greally’s presentation showed.

It would be December 2025 by the time the ramps were rolled out, he said, and in a worst-case scenario, 20 ramps could be installed over 2km. “It could be two less or two more. It just depends on where the public lighting is situated.”

This would cost about €90,000, he said.

Past speed surveys in the Dublin City Council area have shown just how many drivers break limits, particularly on smooth and straight roads that look like they’re made to whip along.

Whether people would adhere to a reduced speed limit on Porterstown Road is not a given, certainly not in the early days of it being implemented, said Carbone-Mangan, the Fianna Fáil councillor, on Monday.

“I don’t think until the actual ramps go in, things will really change,” she said.

That is unless Gardaí are out there carrying out speed checks, she says.

Ramps tend to attract criticism during public consultations, said Leddy on Tuesday. “They can be surprisingly noisy, because they can also be quite bad for your cars going over them regularly.”

But given the seriousness of the situation, it is likely that locals will come out in support of them, he said. “And in my view, the ramps should go in. There really just is a lot of activity on that road.”