To connect the New Territories of the north-east of Hong Kong to the Liantang border crossing in mainland China, the public authorities decided to have a 5.4 kilometres dual two-lane road built, including two 4.8-kilometer tunnels. In order to deal with changing ground conditions along the route Bouygues Travaux Publics and Dragages Hong Kong combined their expertise using several excavation techniques. A first in the history of the group: the widening by excavator of a tunnel section previously bored by TBM. This increase in the diameter from 14 to 17 metres enhances visibility at the tunnel entrance and thus improves safety for future users.