Traffic calming, such as taking out a lane of traffic from each
direction, chicanes and rumble strips, and replacing some of the more
dangerous intersections with roundabouts.
All of these would force cars to slow down.
Yes, but it would make the road more dangerous. Cars would indeed slow down, but that is because the risks are higher. There is no net safety gain (but you do have slower cars).
Hamilton, like the city of Ottawa and kind of like the city of Oshawa, has a series of wide one way streets that allow you to get through downtown pretty quick. The street lights are synchronised to around 50 km/hr, the posted speed limit. During rush hour, they work very well. The problem is out of rush hour when the lights stay green for longer and there is no traffic preventing cars from drag racing between blocks.
Roundabouts do reduce the injury rate of other vehicle occupants at high risk intersections, but they increase the total number of collisions (most are minor) and also are MORE DANGEROUS for pedestrians. After spinning around the intersection, cars have to suddenly stop at a random white line in order to let pedestrians the chance to cross the street. Roundabouts are actually more appropriate on rural roads where speeds are high, traffic is lite and pedestrians are virtually non-existent.
The most appropriate solution to slow cars down is enforcement. If the city can't/wont pay for enough police, then Ontario should consider Alberta's solution of traffic cameras. Making the road more dangerous with "traffic calming" techniques is not the solution.