Self driving buses will be such a boon for public transportation. Now you can have 24 hour buses, that operate on holidays as well, or even dynamic, short term routes based on demand (eg: after a concert or sports event), without being dependent on the availability of pre-allocated human drivers.
Electrical autonomous vehicles don't have a need for a driver and electricity is relatively cheap. So you don't get much economies of scale by making them bigger. Most city journeys would be under a kwh. Even at current grid pricing that's cheap.
Eventually, cheap autonomous vehicles could be mass produced at low cost and would have very low operational cost. So the ride cost would be comparable to, or lower than, current public transport options.
Trains (and train-like options such as metros) are vastly more efficient than cars in number of people moved per unit of time per area used. That might not be a big deal in suburbia, but in dense inner cities it's one of the most important drivers of public transport.
What makes trains efficient has more to do with the cost of energy and drivers than anything else. Both of those go away if you have autonomous electrical vehicles.
Private motor vehicles: 600 - 1600 per hour
Mixed traffic with frequent buses: 1000 - 2800 per hour
Two-way protected bikeway: 7500 per hour
Dedicated transit lane: 4000 - 8000 per hour
Sidewalk: 9000 per hour
On-street transitway, bus or rail: 10000 - 25000 per hour
https://nacto.org/publication/transit-street-design-guide/in...
Usually the comparison comes up in cities where throughput is the limiting factor, and cars end up moving at near-walking pace anyway.
And energy isn't free. If we had any intention of becoming net zero, electricity prices had better increase. And driving around 2t empty weight isn't the way to get there.
Incidentally, a trip that's less than 1 kWh (so, less than 6 km) is a trip that could easily be made on foot or by bike.
A random crappy light rail line will do the equivalent of 5 lanes of traffic (each direction). A serious subway more like 20.
https://visual.ly/community/Infographics/transportation/solu...
Even if you run cars with no distance between the bumpers you'll still need room for changing lanes, crossing and the line.
You also have to take into account all the other factors that make roads preferable, for example, that rail capacity number assumes perfect utilization. In practice railways often have lots of downtime due to overnight shutdowns, broken signals/trains and labor strikes. None of these affect the roads.
Plenty of rail cars have room for luggage too or even baggage cars. Usually we are talking about people going to/from work however hence most people are not carrying lots.
Are you really saying your roads don't have shutdowns for maintenance? Or other problems? Also it is pretty rare for either roads nor railways to be fully utilised overnight. Also note that plenty of rail systems do run overnight.
The lines near me have freight on them (I live in a port city, a noticeable fraction of the country's imports and exports go via intermodal containers on trains) and still run like two services to London and two to other big cities per hour. The freight has to fit in between passenger services, that's a policy decision and the US just picked wrong.
In places with big rail networks you're going to hear "I didn't make it into work this morning because of signal failures" really often. And when railways are repaired they will be totally closed for months. They're just way more brittle and unable to degrade gracefully.
My rando observation is the few times something has gone really wrong on BART traffic is bad enough that it'd be better to take the day off. Ditto if a truck overturns on one of the bridges. And the latter happens way more often than the former. Reminds me after the Loma Prieta earthquake the bay bridge was out for a month but BART was running 12 hours later.
We'll see how this plays out.
2. They will need stop some time. Where? Will this block the street?
3. They won’t all go to the same place so there will be delays at junction and side streets
4. No margin for error wouldn’t fly in practice, so the cars cannot be that close together
5. How will pedestrians cross a train of cars?
I just don’t see how this all adds up. Automation doesn’t remove the space constraints of cars in cities.
A train line has 10x the capacity of a single lane of road. Even if trains are only coming every few minutes, its impossible to compete with a train carrying 1k people with cars. Perhaps reasonably loaded busses would be comparable or better, but that's not the argument you're making.
Trains are financially efficient because of cost of energy and drivers (and, arguably, roads + cars move much of the expense to the public, where as everything related to the train is on the operator's balance sheet), but they are also very space efficient, compared to roads + cars.
If you are not paying for the conductor, can’t you make trains much more appealing? They could run every five minutes, and last mile can be solved with autonomous car that is waiting for you when you arrive.
AVs give us a path toward a world where very few people need to own their own car. We can put all those parking spaces to better use. We can improve equity by giving more people access to safe, reliable, affordable, and convenient point-to-point transportation. Being able to consistently get a ride to where you need to go is something we consistently under-appreciate. It means being able to get a better paying job on the other side of town. Or not having to worry about missing a dialysis appointment, or a meeting with your parole officer or therapist. When the marginal cost of a robotaxi/robobus ride is close to zero is when the AI economic boom will really begin.
Interestingly, no one ever argued for the profitability of cars, so all we can do now is to calculate the overall economic costs and societal benefits and that's where public transport clearly and easily wins.
But the impact of taxis on road traffic in a dense city is comparable to the impact of private cars - perhaps even more so as they're often travelling empty between rides. If every journey which was previously done with a car is done with a taxi, there's no reduction in vehicle traffic - meaning the same problems of congestion and pedestrian safety.
Driverless cars can probably drive closer on highways to increase throughput, but that doesn't really help in cities or residential areas. Ultimately if lots of people shift to driverless taxis to get around, there will be far more vehicles on our streets.