Why won’t councillors let slip lanes slip away?

Last month there were two separate but mirrored debates on removing slip lanes in Galway and Dun Laoghaire-Rathdown, both as part of walking and cycling improvement projects.

A slip lane is a curved lane that allows drivers to leave a straight-through lane of traffic in order to turn left.

While the two projects in Dun Laoghaire-Rathdown and Galway West have been widely supported by both councillors and in public consultation results, full support has been held back by reservations around removing slip lanes.

Ireland’s Design Manual for Roads and Streets (DMURS), which road designers must follow, says that slip lanes should generally be omitted from road design. Junction design has historically prioritised cars, says the manual. “Designers must take a more balanced approach.”

IMAGE: The DMURS includes the above images with the following caption: “Left turning slips (left) generally offer little benefit in terms of junction capacity and increase the number of crossings pedestrians must navigate. They also allow vehicles to take corners at higher speeds, exposing pedestrians and cyclists to greater danger. Where a large number of turning movements occur, left turning lanes (right) with tighter corner radii should be used.”

However, some submissions to public consultations have some councillors touting that removing the slip lane would increase waiting time for motorists in stalled traffic during busy hours.

Council officials, in response to objections, have said that a slip lane’s ability to reduce traffic is generally overstated, and instead, keeping them impacts more highly on pedestrian safety.

What is being proposed in Dun Laoghaire?

Up for debate on Monday, September 11 with the Dun Laoghaire-Rathdown council was the Rochestown Avenue walking and cycle route.

The 2.2km long active travel project from Bakers Corner to the Graduate Roundabout includes two-way cycle lanes, footpath improvement, additional signalised crossings, 175 new trees, exercise equipment, play areas and new benches.

A left turn slip lane westbound from Rochestown Avenue onto Pottery Road would be removed, and replaced with wider footpath and signalised crossings, meaning pedestrians would have a shorter walk across the road. Pedestrians would have to cross a two-way cycle lane onto an island where they would wait to cross Rochestown Avenue.

Cllr Carrie Smyth (Labour Party) said at the meeting that she had reservations about removing the slip lane. “I think it would cause a huge amount of traffic, because the junction is being made tight,” she said.

Two lanes of traffic would be replaced by one, said Cllr Dave Quinn (Social Democrats). “To what extent will the traffic back up, back to Kill Avenue, which will obviously create enormous havoc if the traffic volumes are such to create that level of waiting?”

Cllr Justin Moylan (Fianna Fáil), brought an amendment to retain the slip lane, as removing it would increase traffic. Seventeen of the public’s submissions were concerned with the planned removal of the slip road, he said.

Overall, 157 respondents to the consultation were in favour of the scheme proceeding as is, 63 requested some change, and 28 entries were not in favour of the scheme.

Cllr Tom Kivlehan (Green Party), said that it’s possible that introducing the slip lane would compromise the safety of cyclists and pedestrians. He said that he’d like officials to produce a drawing of the plan before voting on the amendment.

Without the island, pedestrians may not have space to wait, given there is a two-way cycle lane planned at the junction, he said. “The idea of that space there, was to give enough space for people to gather and cross that road safely and timely.”

Conor Geraghty, a senior engineer for active travel with the council, said that if a slip lane was introduced, then the pedestrian crossing green time would be longer, as the road would be wider.

Technically the turning lane could be accommodated, he said, but introducing it would have a marginal impact on capacity.

“Generally, we prioritise the needs of pedestrians and cyclists first, and also try to get in additional planting and green spaces where possible,” said Geraghty, when asked why the council designed the road without the slip lane.

“In this case, we believe the design we’ve put forward is the best design, but that doesn’t mean an amendment that would be passed by the members couldn’t be incorporated,” Geraghty said.

Moylan said that full support for the scheme is held back by the idea of removing the slip lane.

“I believe you will bring a solution in that is correct, safe and workable,” he said. “When the highest number of people making representation on the public consultation is about this one junction, it would be remiss of us not to address that in this chamber.”

The amendment to retain the slip lane was passed 24 votes in favour to 12 against.

What’s proposed in Galway?

Plans for a public realm upgrade to a Galway road and junction were discussed by Galway city councillors in September.

The ‘Part 8 application’ plans, posted in April 2023, show improved footpaths, tightened junctions, resurfacing and the removal of 11 car parking spaces around Sea Road, The Crescent, Father Griffin Avenue, Saint Mary’s Road and Salthill Road Lower.

At the junction of The Crescent and Salthill Road Lower, the council has proposed removing the left turn slip lane, and replacing it with a wider footpath, and adding a rain garden, with trees, shrubbery and soakable paving for water retention. Opposite the slip lane is a doctor’s surgery, a coffee shop, and a primary school. 

In the September meeting, Galway city councillors discussed and voted on advancing the Part 8 application and an amendment asking to keep the slip lane in place and to retain all car parking spaces.

Cllr Peter Keane (Fianna Fail) brought the amendment on the motion on the basis that the slip lane is already pedestrian-friendly, given there is a pedestrian crossing between the island and the footpath.

“It already contains a safety provision to ensure that the children who walk to schools in the area, or others, have a safe mode of transport crossing the road, and that is like any other lighted or sequenced junction,” he said over the phone on 10 October.

The slip lane makes getting around in a car easier, for those who have to drive and who don’t have alternatives, said Keane. Removing the slip lane, he said “is going to add further to the woes of traffic heading westward from the eastern suburbs on a daily basis.”

Cllr Alan Curran (Social Democrats) said over the phone on 9 October, that removing the slip lane at the junction would lead to a safer and more environmentally friendly environment for pedestrians and cyclists.

“It’s a really heavy junction here for traffic,” he says. “There are four schools within 100 metres of this junction, two primary and two secondary.”

Curran said by their nature and design, slip lanes encourage excessive speed. “That road has really narrow footpaths, which means poor precision for walking.”

At the meeting, eight councillors voted in favour of Kean’s motion and five voted against. In voting for the Part 8 proposal, five voted in favour, and eight voted against.

Out of 49 responses to the public consultation on the scheme, 89% of responses were positive and 12% were negative.

Michael Cormican, a Galway City Council executive engineer, wrote a response to the submissions that concerned removing the left slip lane, on August 2.

The schools and businesses at the junction create high footfall at peak hours, he said. Scoil Fhursa and the other businesses make the junction busy with pedestrians, meaning the engineers were focused on improving pedestrian safety.

Cormican said in the written response to submissions that following the instructions in DMURS is mandatory for executive bodies.

The slip lane only helps drivers in periods of low traffic — when there are queues of cars, the slip lane is often blocked for left-turners anyway, said Cormican.

“The model shows that the junction will continue to operate well within capacity with the proposed changes in place,” he says. Removing it would be beneficial, he said, since it causes delays and reduces safety for pedestrians crossing.

“These proposals will help to reduce the likelihood of conflicts between all road users and will encourage a mode shift to sustainable modes to reduce traffic volumes,” he said.

“The Design Manual for Urban Roads and Streets (DMURS) is now mandatory for all Local Authorities with effect of from the date of this Circular for all urban roads and streets within the 60km/h speed limit zone,” states a Department of Transport circular published in 2013, in which the word ‘mandatory’ was underlined.

The manual includes the following on slip turns: “Omit left turn slips, which generally provide little extra effective vehicular capacity but are highly disruptive for pedestrians and cyclists. Where demand warrants, they
may be replaced with left tuning lanes with tighter corner radii.” It added that slip turns “also allow vehicles to take corners at higher speeds, exposing pedestrians and cyclists to greater danger.”


  1. These sort of decisions leave me feeling exhausted. I was thinking about them on my windswept and rainy cycle home today. Perhaps it’s a generational thing. I certainly grew up expecting I’d have a car at some point – which I did – and most people my age do have a car. There’s an inbuilt expectation that default transport is driving – too wet? drive. Too cold? drive. Too long a trip? drive. too awkward a destination? drive. Do we have to wait till all my gen (Gen Xs) hit retirement and can no longer hold public office for this to change? Or do we trust that the default mode will bring its own karmic consequences – increased congestion, more injury and death – until somehow we hit the 100 Monkeys mark and a collective will and readiness to change takes hold?


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