I think the killer combo is self driving cabs for first/last mile, plus rail for intercity travel. Push a button 15 minutes before you want to leave, a cab sits outside your home for up to 30 minutes, you get a warning before each transit sync moment, hop in the cab, get dropped off directly at the platform, get picked up at the designation platform and then dropped at your destination.
It's basically optimal in terms of carbon, throughput, and convenience. Maybe total transit time is no better than a personal car, but you could punch through traffic so at peak times it would be better. And with high speed rail, it could beat personal car even in off peak... At least for some geographies. Obviously if you're not near rail it won't be an improvement in Transit time.