In this location it isn’t even desirable behaviour – a cyclist walking with a bike would fully block the route for some time. A sensible cyclist would ride up to the turn, stop ,wait for any walkers under the bridge, and when clear ride through quickly. There is already a pedestrian priority sign but maybe “Cyclists stop and look out for walkers” would be more explicit.
A pity that unimaginative planers see “Cyclists Dismount” as the solution to all problems – strange that you never see “Drivers push your vehicles”.
On the Good side Hounslow have finally joined the Heath Path to the Hanworth Road