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> The economies of scale you get by packing people in larger vehicles mostly have to do with the cost of fuel and staffing. Trains (and train-like options such

> The economies of scale you get by packing people in larger vehicles mostly have to do with the cost of fuel and staffing. 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.

jillesvangurp 2y ago
Autonomous vehicles could chain up or drive really close together and achieve similar space efficiency. Also, if you look at a train track. It's mostly empty space with a train passing occasionally. Very different than a well used road. And autonomous vehicles could collaborate to counter any congestion. 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.
- drozycki 2y ago
  Not according to civil engineers (it's not even close) 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/introduction/why/designing-move-people/ https://nacto.org/publication/transit-street-design-guide/in...
  - ec109685 2y ago
    That graph those numbers are pulled from should incorporate speed. Otherwise, you could say sidewalks are more efficient than cars.
    - Panzer04 2y ago
      Well, they are - you can move more people with a sidewalk :P. That being said, obviously most people aren't going to walk much more than maybe a km before looking for alternatives. Usually the comparison comes up in cities where throughput is the limiting factor, and cars end up moving at near-walking pace anyway.
- morsch 2y ago
  Urban train tracks see more than occasional traffic, whatever that means. And those trains often carry hundreds of people. Meanwhile, a well used road is well used by huge vehicles carrying 1.2 pax on average. 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.
- slyall 2y ago
  That "train passing occasionally" holds the equivalent of hundreds of cars. 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/solutions-urban-transport 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.
  - mike_hearn 2y ago
    These comparisons are never quite apples-to-apples because the heavy rail line assumes only a few passengers have any luggage and that the entire line is used only for passengers, whereas the capacity rating for a road allows everyone to take large amounts of luggage and freight is always mixed in as well. 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.
    - slyall 2y ago
      You are moving the goalposts here. However if you want to compare mixed freight and passenger lines then rail equals many, many lanes. 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.
      - telotortium 2y ago
        Rail can support freight of course and complements trucks very well. Rapid transit can’t really support freight if it wants to operate at any reasonable frequency - you just can’t load any real quantity of freight in a few minutes. Even baggage is stretching it a lot of the time on busy lines. And the slow acceleration times and length of freight trains severely conflicts with the needs of passenger rail. Therefore, freight and passenger rail need to be separated for either to perform well. On the other hand, cars and trucks are a lot more similar in performance and size, so they can share the same roads just fine - it’s only an issue if the road is completely choked with trucks.
- fire_lake 2y ago
  1. Still not as passenger dense as a train or a bus 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.
- Panzer04 2y ago
  Roads already occupy massive fractions of most cities. Making cars drive closer together or collaborate will make roads environments more hostile to pedestrians than they already are - and arguably in many places we shouldn't even really have private drivers aside from business users on the roads, given the massively disproportionate space they require vs a pedestrian or PT vehicle. 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.

jillesvangurp 2y ago

Autonomous vehicles could chain up or drive really close together and achieve similar space efficiency. Also, if you look at a train track. It's mostly empty space with a train passing occasionally. Very different than a well used road. And autonomous vehicles could collaborate to counter any congestion. 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.

drozycki 2y ago
Not according to civil engineers (it's not even close) 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/introduction/why/designing-move-people/ https://nacto.org/publication/transit-street-design-guide/in...
- ec109685 2y ago
  That graph those numbers are pulled from should incorporate speed. Otherwise, you could say sidewalks are more efficient than cars.
  - Panzer04 2y ago
    Well, they are - you can move more people with a sidewalk :P. That being said, obviously most people aren't going to walk much more than maybe a km before looking for alternatives. Usually the comparison comes up in cities where throughput is the limiting factor, and cars end up moving at near-walking pace anyway.
morsch 2y ago
Urban train tracks see more than occasional traffic, whatever that means. And those trains often carry hundreds of people. Meanwhile, a well used road is well used by huge vehicles carrying 1.2 pax on average. 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.
slyall 2y ago
That "train passing occasionally" holds the equivalent of hundreds of cars. 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/solutions-urban-transport 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.
- mike_hearn 2y ago
  These comparisons are never quite apples-to-apples because the heavy rail line assumes only a few passengers have any luggage and that the entire line is used only for passengers, whereas the capacity rating for a road allows everyone to take large amounts of luggage and freight is always mixed in as well. 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.
  - slyall 2y ago
    You are moving the goalposts here. However if you want to compare mixed freight and passenger lines then rail equals many, many lanes. 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.
    - telotortium 2y ago
      Rail can support freight of course and complements trucks very well. Rapid transit can’t really support freight if it wants to operate at any reasonable frequency - you just can’t load any real quantity of freight in a few minutes. Even baggage is stretching it a lot of the time on busy lines. And the slow acceleration times and length of freight trains severely conflicts with the needs of passenger rail. Therefore, freight and passenger rail need to be separated for either to perform well. On the other hand, cars and trucks are a lot more similar in performance and size, so they can share the same roads just fine - it’s only an issue if the road is completely choked with trucks.
fire_lake 2y ago
1. Still not as passenger dense as a train or a bus 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.
Panzer04 2y ago
Roads already occupy massive fractions of most cities. Making cars drive closer together or collaborate will make roads environments more hostile to pedestrians than they already are - and arguably in many places we shouldn't even really have private drivers aside from business users on the roads, given the massively disproportionate space they require vs a pedestrian or PT vehicle. 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.