Bike paths don’t work in climates unsuitable for biking for large parts of the year. And a train will never achieve the granularity of a vehicle. There are too many use cases where a vehicle needs to access an individual address for the solution to be “just do trains.” In terms of environment, AVs would be drastically more efficient since they could be shared. Again comparing it to rail is silly since a train will never deliver your sofa to your doorstep or wait for you to take your Costco haul of groceries inside.