So it didn’t actually try to route you under the bridge? It gave you a route (presumably via the A171), you chose to divert along Newlands Road and it tried to get you to turn around by going into Hood Lane and using one of the driveways on that lane (before the bridge). You continued along Hood Lane (despite the warnings of 10’ 9" height restriction) and past the unsuitable turning point. If you had been in a lorry, at what point would you have decided to stop and check exactly what you were driving into…?