By the time you're building self-driving car-exclusive tunnels and the like, you really are getting very little benefit over a train system to justify doing it, especially when you take emissions into account.
I'm usually not a person who's sympathetic to complaints about advances in technology eliminating jobs. Not for a real overall long term gain to society. But autonomous cars putting swaths of people out of work while at the same time taking us in the wrong direction on traffic, emissions, etc. doesn't feel great. Those drivers losing work slowly over time as cities evolve truly better and more sustainable transportation options feels more right.
Aside from the opportunity cost of not furthering public transportation, autonomous cars will drive around aimlessly anytime the cost of fuel is less than the cost of parking. We already have Uber creating waste by idling/driving around between passengers.
On the contrary: making taxis cheaper (which self-driving can do, by eliminating the biggest cost - the driver) makes it much easier to live without owning a car.
If there was no Uber and such, I'd probably have to own a car for the exceptions not covered by public transport. And after paying for the fixed costs anyway, the marginal cost per trip is low, making me more likely to use it over PT.
autonomous cars will drive around aimlessly anytime the cost of fuel is less than the cost of parking
Per the above, cheaper taxis → fewer owned cars → more free parking spaces.
Say public transport covers 95% of my needs. If I have cheap taxis, I'll use public transport most of the time, and cars only 5%.
If I have to buy a car because I can't afford those taxi rides, I might use it for 30% or 40% or more of the trips, since it just costs me a bit of gas (or electricity) - the fixed costs are sunk.
- The monthly payment on the car (if applicable)
- Liability / collision insurance
- Gas
- Tolls
- Parking
- Repairs
- Washes
But yes, I'd agree with you that many people don't seem to account for those hidden costs when justifying driving over taking public transit in a city that adequately supports it. Hopefully one day soon that will change.
Big-city issues like parking and congestion charging can tip the scales quite a bit, with much better public transport than the rest of the country to compensate.
We could put effort into making them better but it's not as sexy.
Very high densities are both the problem and the solution. They're the problem because under very high density private car ownership is infeasible, and the solution because public transport becomes fast and affordable. If you let it.
2. Not even building, just repurposing. "This road/lane/whatever now SDV only."
3. Trains only run on rails. Trucks that could be run as SDVs on dedicated infrastructure and as human-driven on shared infrastructure tackle the last-mile problem far more efficiently.
4. Trains are built on the "smart infrastructure" paradigm (go straight at the speed which the signals tell you, until the signals tell you to stop); trucks on the opposite "smart vehicles" paradigm (road exists, everything else is your responsibility). This makes a truck rollout far more scalable (as in "just add this road to whitelist").
Trains work for some freight delivery patterns, but not nearly all. Stuff that can go by train for the most part already does.