> So, an extra car lane a mile long is about an extra half a train, give it take.
The problem with this math is the last mile.
With a road network you have highways with multiple lanes and a lot of traffic, and those branch out into streets with fewer lanes but more destinations.
You can run a train next to the highway and it will achieve much more throughput, but as soon as you get to the offramp, what now? Those 100 passengers all have different destinations that fork off in every direction. You can't run 100 train cars one for each passenger, that's even worse than the road cars. But you also can't just dump them all right there, miles away from where they want to be.
The reason this works in NYC is the density. You can actually get 100 people who are all going to the same place at the same time. Which is also the only way to make it work anywhere else: Build higher density housing. It cannot work in the suburbs because there isn't enough density to run high-occupancy mass transit at a viable frequency.
Whereas in that environment having the occasional four or eight lane highway increases carrying capacity along more than its own length. The single-lane surface streets that branch off in every direction have a vast amount of otherwise unused carrying capacity, which a highway lane unlocks by connecting low-density destinations together. And which you can't unlock with mass transit because those destinations don't have the density for mass transit, even if the path directly parallel to the highway does.
The problem isn't cars or highways, it's zoning density restrictions.
These are all good points. High-density housing makes trains easier. Conversely, trains induce demand for high-density housing near the stations. There are many other considerations that need to be taken into consideration to make trains useful: frequency, right-of-way on road crossings (often a problem for light rail), right-of-way vs cargo trains (long-distance trains in the US), ...
> The single-lane surface streets that branch off in every direction have a vast amount of otherwise unused carrying capacity, which a highway lane unlocks by connecting low-density destinations together. And which you can't unlock with mass transit because those destinations don't have the density for mass transit, even if the path directly parallel to the highway does.
In a lot of suburbia, there are large parking lots near train stations. In theory, your point is a great advertisement for this setup. In practice, I never lived in a place where driving to the train station was convenient, but it's quite possible that is an accident. For one, parking lots have to be truly large to fit the number of people that would fit in a train car.
> Conversely, trains induce demand for high-density housing near the stations.
The primary existing problem is that high-density housing is prohibited through zoning, or made prohibitively expensive through other regulatory rules. It doesn't matter how much demand you generate if increasing supply is constrained by law. Whereas if you could fix the zoning and building codes then you wouldn't need to induce demand because demand is already there -- it's why housing is so expensive.
> There are many other considerations that need to be taken into consideration to make trains useful: frequency, right-of-way on road crossings (often a problem for light rail)
These are all density again. You get frequency by having enough passengers to fill the transit car on that interval, which you get from higher density. There is no point in sending a bus to carry one person to one house, it might as well be a car.
This is also why right of way and bus lanes are the wrong way to think about it. If you don't have enough density you're going to lose regardless and all the bus lane is going to do is make the traffic worse, because people can't take the bus if it doesn't go where they're going when they're going there and then you're just wasting a lane. Whereas if you do have the density then you still don't build a bus lane because instead you build a subway.
> In a lot of suburbia, there are large parking lots near train stations. In theory, your point is a great advertisement for this setup.
That's trying to have it both ways. If you have to drive to the train station then you have to buy a car and insure it and unless the parking at the train station is free you're now paying for parking. At this point people start wondering why they're hoofing it up to the train platform and paying for transit tickets and waiting for the train instead of just driving the rest of the way to their destination.
To fix this you need more people to live within walking distance of mass transit. Which is to say, you need to build higher density housing or allow mixed zoning so people can live closer to where they work.
>At this point people start wondering why they're hoofing it up to the train platform and paying for transit tickets and waiting for the train instead of just driving the rest of the way to their destination.
Usually, it's because
1) the highway to their destination in the city center has too much traffic, and the train is faster, and
2) there's no parking at their destination, and no place to build it at any kind of affordable price.
Just look at Washington DC: tons of people commute by car to suburban train stations, pay a monthly fee to park in the big parking garages there, and then commute the rest of the way into the city center by train to work in government offices.
The problem with this math is the last mile.
With a road network you have highways with multiple lanes and a lot of traffic, and those branch out into streets with fewer lanes but more destinations.
You can run a train next to the highway and it will achieve much more throughput, but as soon as you get to the offramp, what now? Those 100 passengers all have different destinations that fork off in every direction. You can't run 100 train cars one for each passenger, that's even worse than the road cars. But you also can't just dump them all right there, miles away from where they want to be.
The reason this works in NYC is the density. You can actually get 100 people who are all going to the same place at the same time. Which is also the only way to make it work anywhere else: Build higher density housing. It cannot work in the suburbs because there isn't enough density to run high-occupancy mass transit at a viable frequency.
Whereas in that environment having the occasional four or eight lane highway increases carrying capacity along more than its own length. The single-lane surface streets that branch off in every direction have a vast amount of otherwise unused carrying capacity, which a highway lane unlocks by connecting low-density destinations together. And which you can't unlock with mass transit because those destinations don't have the density for mass transit, even if the path directly parallel to the highway does.
The problem isn't cars or highways, it's zoning density restrictions.