The A156 is an 11 miles (18 km) long road that runs from the A57 near Saxilby and heads north to Gainsborough.

It is a single carriageway for its entire length apart from one small stretch at Torksey Lock where the A1133 joins from Newark-on-Trent.

The road starts just west of Saxilby where it branches off from the A57 from Lincoln.

The A1133 from Newark-on-Trent merges with the road slightly further on where it makes a sharp turn and heads north alongside the River Trent and the border with Nottinghamshire.

The A156 continues on to Lea where the B1241 joins from Saxilby then the road heads into Gainsborough where it terminates just south of the centre at the A631.