I think you are right, there will be a tipping point at some stage. For something that is so thoroughly baked into the American way of life, I think 20 years i

I think you are right, there will be a tipping point at some stage. For something that is so thoroughly baked into the American way of life, I think 20 years isnt a bad estimate. I'm not totally up on autonomous car tech, but while very promising, it still seems to be proof of concept stage. To me that means ~10 years from commercializarion, and then at least 10 years before it has penetrated enough of the fleet that you can even start to consider making it mandatory. Automotive engineering is conservative because of the scale and age of the industry, the cost of the goods sold, and the risks inherent in their failure. Automobile owners are conservative because cars are big purchases. The thing about timeframes like that is that there are enough unknowns that estimates can easily be 2x too optimistic. I tend to agree that rail (whether urban light rail, or region high speed rail) may not be the most cost effective way to move a lot of people from point a to point b given existing patterns of development, I know that part of the reason planners favor it is that its cost comes comes as part of a permanence that can shape the way communities develop around it over the long term.