If she's trying to explain why they might be able to place him near the lock-up, she might mean the footbridge over the A15 at the end of Willesden Avenue (near Montagu Rd) which then passes under the A47 and then up over the A15 again on the other side, towards Westwood. As he was driving afterwards.Is the footbridge the one over the railway line that runs parallel to Westfield Road? If so, it's not far from where BW's phone was used to text SaW's phone near the prison at 3.33pm on the 19th. Were they (he) trying to make out BW was staying at a location somewhere in the Westwood area? The footbridge and Westwood doesn't match up at all with what they told police had happened on the journey home.
I got the feeling Westwood might be near her ex-boyfriend's home, but it's purely a guess.