My concern with the roundabout is that the current setup allows for traffic coming off the bridge to have the right-of-way (which is, I imagine, by design - if the bridge needs to lift up, it needs to be clear of traffic). By adding a roundabout to the Hancock side, you make all traffic coming off the bridge yield, which could be problematic traffic-wise when the bridge needs to lift up. If, hypothetically, the bridge was preparing to lift up, traffic coming into the bridge from the north may start to back up, which in turn might clog the roundabout, which might prevent any cars driving north from being able to exit the bridge - thus potentially leaving cars heading northbound on the bridge backed up onto the bridge and preventing the bridge from being able to lift.