The B5421 is a short link road in southwest Lancashire. It was originally unclassified but gained its number in 1935.
The road starts on the A565 Crosby Road South and heads southeast along the residential Sandringham Road. This road is one-way in this direction. Soon we reach Cambridge Road and the B5421 bears left to follow it. Cambridge Road is also the route back to the A565 but this is unclassified.
We soon bear round to the right to avoid crossing the railway line then head southeast along Sandy Road to reach a mini-roundabout. Originally the B5421 continues along Sandy Road (which now lies to the left) to end on the A567 Seaforth Road near the station. Now, however, the southern end of the route has been rerouted along Ewart Road to cross over today's dual-carriageway A5036 to bear left onto Church Road and end on Seaforth Road, which is now unclassified.