Here's how the new M50 variable speed limits will work

The new system is expected to take full effect on the motorway by early 2023.

LAST UPDATE | Sep 17th 2021, 2:31 PM / YouTube

A PHASED INTRODUCTION of different speed limits on the M50 will begin to take effect over the next few weeks, the Transport Minister has announced. 

Under new plans for the motorway, operators will be able to better slow traffic in response to crashes, roadwork, poor weather conditions and congestion. Drivers will be notified of changes through new digital signs.

It is aimed to keep drivers better informed about incidents ahead and how these might affect their journey. It is also aimed to improve safety on the road.

The new system will mean that different lanes may have different speed limits at different points along the motorway depending on whether an incident may be up ahead. 

There are to be 19 new gantries over the roadway to keep motorists informed with a total of 386 lane control signals.

Transport Infrastructure Ireland (TII) communications director Sean O’Neill said today that the new system would make for a “safer and more efficient” M50. 

O’Neill said the motorway is perhaps the most critical part of Ireland’s road infrastructure and is “an Achilles heel for the country” in that “it has to function well”. 

TII said the new system will improve journey time reliability by reducing the number of times vehicles need to stop and start on the motorway, and reduce the need for drivers to brake suddenly when traffic comes to a stop. 

TII says the new system will improve traffic flows because tailbacks are often caused by the “accordion effect” of motorists slowing speed suddenly in response to an incident or blockage up ahead.

The new system should instead bring motorists down to an appropriate speed long before they come upon an incident, avoiding the need for sudden breaking and the tailbacks this causes.   

Transport Minister Eamon Ryan was today present at the launch of the plans, which will see the new speed limits apply on an advisory  basis before laws will be passed by Christmas to make them “mandatory and enforceable”. 

“It’s starting on an advisory basis which is right, it’s appropriate test to make sure the whole system works. But myself an Minister Naughton will be introducing legislation or due to introduce legislation in the Dáil this term which would put it into statute, into law,” he said. 

O’Neill from TII said gardaí will enforce the new variable speed limits and that M50 traffic cameras will be used only to monitor road conditions and not used to catch speeding motorists. 

“What this is for is for implementing a safe environment, the enforcement elements will be still carried out by an Garda Síochá on site. These cameras will not be used for that. They’re for monitoring, for data collection, so that if an incident occurs, we can respond immediately with the information to the driver in real time, that’s what they’re for,” he said. 

O’Neill added limits may be as low as 30 km/h if required. 

The new system will have a five-phased rollout, with the first phase beginning in the coming weeks. 

  1. Autumn 2021 - J4 Ballymun to J6 Castleknock
  2. Spring 2022 - J6 Castleknock to J9 Red Cow
  3. Summer 2022 - J9 Red Cow to J12 Firhouse
  4. Autumn 2022 - J12 Firhouse to J14 Sandyford
  5. Winter 2022 - J14 Sandyford to J17 M11 and J3 M1 to J4 Ballymun

TII chief executive Peter Walsh said today that new system will also make it safer for emergency services to response to incidents on the motorway. 

It’s all about safety, you’ve seen the incidents and anyone who uses the M50 will be aware of just how hazardous it can be. And the men and women of the motorway operations, the fire service, gardaí, the ambulance service go out there and deal with those incidents. So this system, which will advise drivers of the appropriate speed to be driving at when an incident occurs is one that will make it safer or all of those people involved. 

“We have 400,000 trips a day on the M50 and where you see levels of congestion it is very that’s disruptive. And you get this with a wave of  stop-start start driving, it does affect efficiency.” 


M50 traffic levels are now back to around 95% of the levels in September 2019, figures show. 

Trips on the motorway rose by 40% between 2011 and 2019 and before the pandemic, there were approximately 400,000 journeys taking place each day. 

The busiest section of the M50 was between the N2 interchange at Finglas and the N3 interchange at Blanchardstown.

The phased approach to the new system is aimed to help drivers get used to the new system and adjust their driving in advance of regulatory speed limits. 

The system is expected to take full effect on the M50 by early 2023. 

- Additional reporting by Orla Dwyer.

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