The US$35.5 million strengthening project is part of an ongoing maintenance programme. "The clip-ons are stronger today than when they opened. We are reinforcing them so they continue to meet the growing traffic demand," says northern network operations manager Joseph Flanagan.

Preparation work includes improving access, ventilation, lighting and power supply for the construction workers who will be working on the clip-ons.

Strengthening work will start in July and will take approximately two and half years to complete. The work will involve fixing more than 700t of steel to the box girders.