As a resident of Derby Hill Crescent with 2 toddlers one would assume I would be for the proposal. But I see NO point. The speeds on the Derby Hill / Derby Hill Crescent are less than 20 mph already. These are steep hills in part and if there is a vehicle on the opposite side, one needs to stop (almost park) to pass through. The speed humps would be completely ineffective as passing cars can not possibly go faster than 20 mph. And if you get to be driving behind me on Thorpewood Avenue, you would not go faster again.
My biggest gripe is with the hump by the Library. It is so high and no matter how slowly you go over it the ride is rather uncomfortable. With both of my pregnancies in the latter stages this was avoided at all cost. Imagine a journey in an ambulance and when in pain. Those humps just hurt even more.
Lastly this is proposed to increase cycling in the area. You need to be pretty fit to walk up the Derby Hill, let alone try to cycle up it.