The main improvement to the traffic flow will be the double yellow lines on both sides of the street, particularly towards the north end.
Improved pedestrian space and crossings will make the street more attractive to shoppers, with slightly increased numbes of parking bays and length of stay. Although this is a through road, it is also the heart of the town centre and the primary objective for Dartmouth Road should be a place that people want to visit, rather than driving to Bell Green for all their shopping.
I’m not a highway engineer, so I’m not sure the exact impact on road speeds and jams, but i think there is a school of thought that says slower speeds regulate flow and reduce the build up of jams. That does depend on the outflow from a particular section, and Dartmouth Road northbound is still limited by the flow on to the junction with the south circular. Speed calming, bus stops, and narrow streets will have little impact on that bottleneck. And with the double yellow lines the flow should actually improve.
Some people have suggested that the double yellow lines won’t work and people will park there anyway. Personally i doubt it will be such a problem and the narrower road will actually stop this from happening as anybody parking on the double yellow will be completely blocking traffic flow (unless they are right on the pavement). The aim is certainly not to increase jams, it is actually hoped that it will improve flow, but that might be too much to ask for on a road that is often a 500m queue northbound.
No scheme could solve all the problems on this road and this scheme is an attempt to balance the needs and safety of drivers, bus users, pedestrians, cyclists, traders, and shoppers. At the moment the road is incorrectly balanced in favour of inconsiderate parking and against pedestrians and shoppers. I’m hopeful that the scheme will be positive for almost everybody, including drivers.