The pigeon debate is being aired again.
Several solutions to the problem of getting rid of the birds have been offered.
My own solution to the problem would be in the first place to cover the whole of the area under the bridges where the birds are roosting with fine chicken wire and at the same time to erect wooden roosting boxes attached to long iron poles on areas of grassland away from the public footpaths.
Pigeons usually go for the highest point to roost or nest, finding their usual site unavailable they could probably easily colonise these boxes.
There would be problems to overcome but I think it would be worth trying. Live and Let Live.