Restricting access to and from the central motorway (near Swan Hose Roundabout) will increase the risk of accidents at other junctions.
I've spotted that the slip road north from the B1309 is already an accident black spot for red end shunts.
Have you considered reducing speed limits on some of the roads? This would reduce pollution as vehicles would be accelerating less and travelling more efficiently.
Some of the existing measures actually generate more traffic and and congestion and pollution, so measures must be very carefully re-evaluated. Classic example is the regular grid lock outside the front of Newcastle Central Station - it's to possible to set passengers down with out driving around the block in front of the station first.