As there was no towpath, "legging" was the only means of propelling the boats. The bargees had to lie on their backs and push against the roof and wall with their feet, taking about three hours to accomplish the hazardous journey. The horses would be led over Harecastle Hill, using the route now known as Boat Horse Road. The opening of the tunnel completed a system of navigation that provided transport for raw materials and manufactured goods at an estimated cost of one-quarter that of land transport.

The proposed introduction of railways necessitated improvement of canal transport, and a decision was made to drive a second tunnel through Harecastle Hill. This runs parallel to Brindley's and was designed by Telford. This disappointing block-shaped building conceals the entrance to this very fine engineering feat. Telford's tunnel runs in a dead straight line for 2,962 yards and consumed nearly 9 million bricks in its construction. It was opened on April 30th, 1827, after 3 years' hard work. The inclusion of a towpath enabled barges to be towed by horse and so accelerated the treacherous journey through the blackness."