I don't know.
I remember when they weren't there - they were introduced just after the one way system and to me the one way system was the thing that made the driving safer in the area. But one downside of one way streets is that people can bomb down them without slowing down for people coming the other way - hence (I guess) the bumps.
I was just marvelling at the wondrously smooth road that is now Hewitt the other day. Does anyone know what the intentions are as regards the humps?
Enjoy Warham while it lasts, must be lovely!