History, purpose and how we maintain it
The Cuilfail Tunnel is a key part of the A26 in Lewes, connecting Phoenix Causeway to the A27 at Southerham Roundabout. It helps traffic move efficiently around the town, reducing congestion through the historic town centre.
At around 430 metres long, the tunnel runs through the chalk hills to the East of Lewes.
A brief history
The tunnel opened in 1980 as part of improvements to the road network designed to bypass the historic centre of Lewes and improve journey times.
Plans for a route around Lewes date back much earlier, with proposals developed in the mid-20th century before construction was approved and completed.
Since opening, the tunnel has undergone significant upgrades to keep it safe and fit for modern use. This includes a major refurbishment completed in 2010, which improved lighting, replaced interior cladding and helped extend the life of the structure.
More recently, further improvements such as energy-efficient LED lighting and upgraded systems have been introduced to improve safety and reduce environmental impact.
Keeping the tunnel safe and operational
The tunnel is one of East Sussex’s specialist highway structures and requires regular and carefully planned maintenance.
To keep the tunnel safe for everyone who uses it, we carry out regular maintenance activities, including:
- Quarterly cleaning of the tunnel interior
- Washing of walls and cladding panels
- Road sweeping and debris removal
- Vegetation clearance at the tunnel entrances
These activities help improve visibility, maintain the condition of the structure and ensure a safer driving environment.
In addition to cleaning, the tunnel is regularly inspected and monitored to make sure everything is working as it should. This includes:
- Checking lighting systems and controls
- Inspecting ventilation equipment, such as jet fans
- Reviewing drainage systems and clearing water outlets
- Carrying out general structural inspections
This work is carried out during planned overnight closures to minimise disruption to road users.
Why closures are needed
You may notice that the tunnel is closed every three months. These closures are essential to allow maintenance teams to safely carry out inspections, repairs and cleaning.
Because of the confined space and specialist equipment involved, this work cannot be carried out safely while traffic is using the tunnel.
Closures are carefully planned and typically take place overnight to reduce inconvenience, with signed diversion routes in place.
Much of the work to maintain the Cuilfail Tunnel happens behind the scenes, but it plays a vital role in keeping the network safe and reliable.
On occasion, emergency services may use these closures to carry out training exercises.
Scheduled maintenance programme
Find out more
Information on tunnel closures are shared on our social media channels and One.Network