Knights Brown Starts Castle Street Upgrades Feb

Key Points

• Long-term changes are coming to Castle Street, with construction work set to make the temporary road layout and cycleway permanent.
• Site surveys and removal of traffic islands on Kingsway will precede the main construction phase towards the end of February.
• Initial preparation work starts on 2 February, focusing on surveys and site setup.
• Main construction phases begin on 23 February and are expected to take around 52 weeks to complete.
• Cardiff Council has appointed Knights Brown to deliver the scheme.
• Castle Street and the existing pop-up cycleway will remain open to traffic in both directions throughout most works, with closures only during resurfacing and advance notice provided.
• The current number of traffic lanes on Castle Street will stay the same, with no reduction planned.
• Detailed assessments confirm Castle Street must remain open to avoid wider city disruption, including impacts on bus times near Cardiff Bus Interchange, pressure on Central Link, Eastern Bay Link Road (with Hemingway Road closed), Butetown Tunnels, and Gabalfa Roundabout at peak capacity.
• Future Cardiff Crossrail project leaves no spare capacity for displaced traffic.
• Permanent scheme upgrades include a fully segregated cycleway to Active Travel standards, carriageway resurfacing, upgraded footways and paved areas, bus stop layout changes on Kingsway and North Road, enhanced bus infrastructure, green roof bus shelters, extra landscaping, and traffic management for better air quality.
• Castle Street has focused on air quality improvements since 2018, when Nitrogen Dioxide levels breached legal limits, prompting Welsh Government to direct Cardiff Council to develop a Clean Air Plan.
• Temporary layout reduced lanes from three to two, retained westbound bus lane, and added two-way cycleway, dropping NO2 from 45 to 29 micrograms per cubic metre, within legal standards.
• Cllr Dan De’Ath, Cabinet Member for Climate Change, Transport and Strategic Planning, stated the temporary layout succeeded in reducing pollution and meeting legal requirements.
• Public consultation showed over half of respondents supported reopening the road after its pandemic closure as an outdoor café space.
• Funding confirmed enables permanent scheme.
• Junction improvements on surrounding roads: new segregated cycleway and pedestrian crossings at Westgate Street; layout improvements and cycle parking along Castle Street; paving and street furniture near Cardiff Castle on High Street; upgraded bus stops, crossings, and landscaping at Kingsway; replacement tree planting where needed.
• Completed scheme supports cleaner air, safer travel, better public spaces, sustainable city centre movement, while maintaining traffic flow.

Cardiff (Cardiff Daily) January 30, 2026 – Cardiff Council has announced that construction to make Castle Street’s temporary road layout and pop-up cycleway permanent will commence in February, with initial surveys on 2 February and main works from 23 February for about 52 weeks. Knights Brown has been appointed as the contractor, ensuring Castle Street remains open to bidirectional traffic during most phases, barring resurfacing closures with prior notice. The project addresses air quality, safety, and accessibility while avoiding broader traffic disruption.

When Will Construction Start on Castle Street?

Initial preparation work, including site surveys and setup, begins on 2 February. The main construction phases follow on 23 February, projected to last approximately 52 weeks. Cardiff Council confirmed these timelines in their official announcement, following completion of site surveys and traffic island removals on Kingsway.

Throughout most works, Castle Street and the cycleway stay accessible to traffic in both directions, preserving the existing lane count without reductions. Closures occur solely during resurfacing, with advance warnings issued.

Why Is Castle Street Staying Open to Traffic?

Following detailed assessments, Cardiff Council determined Castle Street must remain open to prevent city-wide disruption. Closing it would extend bus journey times near Cardiff Bus Interchange, heighten pressure on Central Link and Eastern Bay Link Road amid Hemingway Road’s ongoing closure, and overload Butetown Tunnels and Gabalfa Roundabout, already at peak-hour capacity. Planned Cardiff Crossrail further eliminates spare traffic capacity.

The council’s evaluation underscores no viable alternative to sustain network flow.

What Upgrades Are Planned for the Permanent Scheme?

The scheme features a fully segregated cycleway meeting Active Travel standards, full carriageway resurfacing, enhanced footways and paved areas, and revised bus stop layouts on Kingsway and North Road. Further enhancements comprise improved bus infrastructure, green roof shelters, additional landscaping, and traffic adjustments targeting air quality gains.

These measures prioritise safety, accessibility, and cleaner air.

How Has Castle Street’s Air Quality Improved?

Castle Street targeted air quality since 2018, when Nitrogen Dioxide (NO2) levels exceeded legal limits at 45 micrograms per cubic metre. The Welsh Government then mandated Cardiff Council to produce a Clean Air Plan.

A temporary layout cut lanes from three to two, preserved the westbound bus lane, and introduced a two-way cycleway. NO2 subsequently fell to 29 micrograms per cubic metre, complying with standards.

What Did Cllr Dan De’Ath Say About the Project?

Cllr Dan De’Ath, Cabinet Member for Climate Change, Transport and Strategic Planning, said the temporary layout has proven successful in reducing pollution and meeting legal requirements. He noted that public consultation revealed more than half of respondents supported reopening the road after its pandemic use as an outdoor café space. With funding now secured, the council proceeds to permanence.

Which Contractor Handles the Works?

Cardiff Council appointed Knights Brown to deliver the scheme, overseeing preparation from 2 February and main phases from 23 February.

What Junction Improvements Surround Castle Street?

Adjacent upgrades include a new segregated cycleway and pedestrian crossings at Westgate Street; Castle Street layout enhancements with cycle parking; paving and street furniture updates near Cardiff Castle entrance on High Street; and Kingsway bus stop, crossing, and landscaping improvements. Replacement trees compensate for any removals.

How Does This Fit Cardiff’s Broader Goals?

The council states the scheme fosters cleaner air, safer travel, superior public spaces, and sustainable city centre movement, while preserving wider traffic operations. It builds on temporary successes to deliver enduring benefits.

What Triggered the Original Air Quality Action?

In 2018, pollution breaches on Castle Street prompted Welsh Government intervention, directing a Clean Air Plan and temporary measures that halved lanes and added cycling infrastructure, yielding compliance.

Will Traffic Lanes Reduce During Construction?

No reductions planned; lanes match current setup, with Castle Street and cycleway bidirectional except resurfacing.