With all the traffic problems in big cities, I think we need something to help the flow of traffic at a fundamental level at the stop lights. How many times have you seen people leaving way too much space between cars at a stop light, causing the line to be much longer than necessary. Then when the light turns green, the first car departs, a few seconds later, the second, then the third, etc. Just a simple system where your car senses the car in front of you so a platoon of cars can all leave the light simultaneously when the light turns green would help ease the congestion.
Then the next problem is the sheer size of our vehicles. The Mini Cooper is no longer Mini. Today's civics are the size of accords from a decade ago. The CTS used to be a mid-sized car, now its huge. Yes, there are smart cars, but when everyone else is in and SUV, you don't want to be SUV bait. It everyone drove a smart car-sized vehicle, then the fear of getting squashed goes down.
I think big cities need to start banning icers and only allow pure EVs. People coming in from out-of-town will need to mark in Disneyland-like parking lots and take light rail into town. An EV only push would most certainly accelerate adoption.