Flying Dodo
It'll soon be summer
I notice you can't actually back up your assertion that traffic speed through the roundabout is reduced. It looks to me like the complete opposite would be true. There's a reason why in the Netherlands, cycling routes completely bypass these turbo roundabouts - because they are provision for motorised traffic and not cycling.
As I've made clear, I was merely quoting the Bedford Council Officer and provided the link to his explanation about why vehicular speeds should be lower. As I've already stated, I have to assume he knows about traffic.