Year-long roadworks to get underway on key Cardiff route

Construction work to make long-standing temporary road and cycling changes on Castle Street in Cardiff permanent is set to begin in February, with the main phase of the project expected to last around a year.

Initial preparatory work will start on February 2, focusing on site surveys and early groundwork, including the removal of traffic islands on Kingsway. The main construction phases are scheduled to begin on February 23 and are expected to take approximately 52 weeks to complete.

Cardiff Council has appointed Knights Brown to deliver the scheme. Throughout most of the works, Castle Street and the existing pop-up cycleway will remain open to traffic in both directions, except during short periods of resurfacing. Any temporary closures will be communicated to the public in advance.

The council has confirmed that the current configuration of traffic lanes on Castle Street will remain unchanged, meaning there will be no reduction in the number of traffic lanes as part of the permanent scheme.

Following detailed transport assessments, the authority concluded that Castle Street must remain open to traffic to avoid significant disruption across the wider road network.

The council warned that closure would have a disproportionate impact on bus journey times, particularly for services using Westgate Street and Customhouse Street to access the Cardiff Bus Interchange. Additional pressure would also be placed on the Central Link and Eastern Bay Link Road, especially given the ongoing closure of Hemingway Road.

Further concerns include existing capacity issues at the Butetown Tunnels and Gabalfa Roundabout during peak hours, as well as the planned reallocation of road space to accommodate the Cardiff Crossrail tram system, which would leave little spare capacity for displaced traffic.

The permanent scheme will include a fully segregated cycleway built to Active Travel standards, resurfacing of the carriageway along the route, upgraded footways and paved areas, and changes to bus stop arrangements on Kingsway and North Road. Measures aimed at improving air quality will also be introduced, including traffic management changes, enhanced bus infrastructure, green-roof bus shelters and additional landscaping.

Castle Street has been a particular focus for air quality improvements. In 2018, nitrogen dioxide levels exceeded limits set under the European Ambient Air Quality Directive, prompting the Welsh Government to legally direct Cardiff Council to produce a Clean Air Plan. A temporary road layout was introduced to meet those requirements, reducing traffic lanes from three to two, retaining a westbound bus lane and installing a two-way pop-up cycleway.

Since the changes were made, nitrogen dioxide levels have fallen from 45 micrograms per cubic metre to 29, bringing the street into compliance with air quality standards.

‘Effective’

Cabinet Member for Climate Change, Transport and Strategic Planning Cllr Dan De’Ath said the temporary scheme had proven effective.

“The revised layout has significantly reduced NO₂ levels and ensured we remain legally compliant,” he said. He noted that during the pandemic the street was closed to traffic and used as outdoor café space, but more than half of respondents to a later consultation supported reopening it.

“With funding now confirmed, we are making the temporary scheme permanent to meet air quality requirements, improve safety and accessibility, enhance the public realm and support more sustainable travel,” he added.

Junction improvements 

As part of the project, junction improvements will also be carried out at Westgate Street, High Street and Kingsway, including new pedestrian and cycle crossings, upgraded paving, revised traffic movements, additional cycle parking and green-roof bus shelters. Replacement planting will be provided where trees are removed.

The council says the completed scheme will help reduce congestion, cut traffic-related emissions and create a safer, more accessible city centre route.