How Engineers Delivered the UK’s Heaviest Bridge Slide Ahead of Schedule

The A46 Kenilworth Bypass in Warwickshire has reopened—30 hours earlier than planned—following the successful completion of a record-breaking bridge slide. Over an 18-day full road closure, engineers executed the UK’s heaviest bridge slide to date, installing a 14,500-tonne concrete box beneath the dual carriageway to carry high-speed rail services between London and Birmingham.

Rather than opt for a traditional bridge build, which would have involved two years of lane closures and speed restrictions, the project team chose an innovative solution: constructing the massive box structure adjacent to the road and sliding it into place using Autoripage, a specialist jacking system. The entire 64-metre push was completed in just 10 hours, at a pace of 6.5 metres per hour, using 15 precision jacks.

What made this engineering operation stand out wasn’t just its scale—it was the detailed planning, risk management, and coordination behind the scenes. The initial phase saw the demolition of a 200-metre section of the old road and the removal of 35,000 cubic metres of earth and sandstone to create the space for the new structure.

Once positioned, the bridge slide involved injecting bentonite—a clay-based lubricant—into strategically placed holes at the base of the box, reducing friction and enabling a smooth transition. Even with the complexity of aligning a structure of this magnitude, the project team delivered the operation with millimetre precision, ensuring both stability and safety.

While the bypass is now open, minor lane closures will remain in place until July to allow completion of the central reservation and wingwalls—final touches to a project that has already demonstrated exemplary engineering execution.

This bridge is just one of more than 200 major crossings on the HS2 high-speed rail network, a transformative infrastructure project designed to expand rail capacity, cut travel times, and reduce pressure on existing lines. By using advanced civil engineering techniques to minimise disruption to existing road users, the A46 project sets a new standard in infrastructure delivery.

With more than 31,000 people employed across the HS2 supply chain, this milestone is a symbol of how innovation, collaboration, and meticulous execution can redefine what’s possible in civil engineering.