I don't think roundabouts/ rotaries should be placed in the city or busy residential areas with pedestrians. They are more for outside the city, on busy road's where it's pretty much all vehicle traffic. In the city it's alot of pedestrian traffic, so these road systems don't work as well.
I think one of the problems in Halifax is people (government or public) don't understand a rotary, or roundabout or how they work best. They think it works fine in one situation, so it must work fine in another situation. By the sounds of it, Halifax councillors want to put them everywhere. But you can't really do that as alot of areas have alot of pedestrian traffic. Alot of intersections these roadways are proposed would be just fine with a set of lights.
In a city, even with a rotary, traffic would back up (maybe not as bad as an intersection) but traffic would still be slow as you have pedestrians crossing, cars going around the circle, cars would have to wait to enter, plus all kinds of roads coming into the rotary etc. etc. (Plus you'd have those with zero patience and just go, not waiting for an opening. Or those not knowing how the circle works, thus slowing everyone down.) It's not as efficient in a city as it would be on a highway or less populated area etc. Where a roundabout/ rotary is more suited.
Even when you look at Columbus Circle in NYC... It has lights to help control traffic. So lights are not all bad
Maybe this is what Halifax needs to do in it's more busy intersections in the city. Have a roundabout with lights. This way pedestrians can still have a chance to cross without having to be scared to death.
Something like Columbus Circle.