Protected and separated car, bike, and pedestrian lanes. I've been to a lot of cities and hands-down the best street I've ever been on is the Karl Marx Alley in Berlin, with is absurdly wide lanes and tall apartment complexes and storefronts. We're talking about having playgrounds in the area between the lanes.
1. Make a town whereby the sidewalk and the street is reversed; that is, the pedestrians walk in the center of the street, stopping at lights, while the cars use the sidewalks (very wide sidewalks of course). There might or might not be bicycle lanes. You wouldn't have to make the center street for pedestrians wide, but it's the pedestrians that get the lights while the cars have to use the cross(walk?).
2. Subsidize electric bicycles and scooters instead of these huge construction projects.
Example 1: my old town St Louis recently built a 2.2 mile trolley at the cost of over 65 million dollars. This trolley ludicrously runs parallel to a light rail trolley from the same station to the terminus.
Example 2: my new town Montgomery just put in a 140 million dollar overpass that serves 800 houses, essentially costing about 175,000 per house. I've never seen a single car on these two overpasses. Not once. It's completely deserted; to actually use these two overpasses you'd have to drive out of your way to get to them if you were in those 800 houses, as those houses are already being served by two north/south and one east-west arterial road.
3. Place speed limitators in all vehicles that set themselves via GPS to the road speed limit.