Canada

Maybe some day in the distant future our policy-makers will understand that updating a few signs doesn’t make a damn difference.

Yes it does, even if compliance is low, and the reason is what you yourself is saying

You need physical speed reduction methods such as speedbumps, roundabouts, raised crosswalks, etc.

Traffic engineers won't do these road diets on 50km/h streets. Changing the speed limit is an important first step that enables further changes to road infrastructure to help enforce the updated speed limits. This sweeping change is a MAJOR victory, that has been argued for many years. That we were able to pass this for so many neighbourhoods at once is great news and should be celebrated.

This was discussed at length during the council meeting, including later in the same day where another vote was passed to update the commitments and plans for the municipal Vision Zero initiative, which are in fact going to require infrastructure projects.

What about just enforcement?

They actually changed the road to accommodate mixed usage while lowering it? Lucky you!

Here there just taking big roads designed for 50, and making them 40 with zero plans to change the roadway to encourage the lower speed.

Fully closing some streets to vehicle traffic also helps. It not only reduces collisions but also increases vehicle throughput.

The change in Vancouver is specifically aimed at minor streets though, where other traffic calming measures are usually already in place. And the reduced speed is a climate measure more than a safety measure.

People are downvoting you because your question is implying driver delays are not worth the increase in safety. Drivers are often protesting nearly anything that slows them down even when that thing slowing them down has been proven to save lives.

Not much overall I would guess. Most people going 60-70 in a 50 zone usually just end up getting to the next red light faster, wasting their gas and wearing down their brakes faster.