From that searching I came across the following article. Now this article has a clear bias (but so do the people advocating for rail), but bias doesn't mean that there aren't valid points being made even if exaggerated. Curious what your response is to their counter claims:

https://www.washingtonpolicy.org/publications/detail/sound-t...

One thing that stands out is that ST3 is saying it is a theoretical limit of 16,000 pphd not 30,000. Where did you get the 30,000 figure from?

> The problem is that Sound Transit officials are comparing 16,000 humans to 2,000 vehicles.

This is actually not that bad of a comparison; most Americans drive alone. The FHA, hardly some anti-car agency, estimates car occupancy at 1.54 persons a vehicle, and overally light-vehicle occupancy at 1.67 persons a vehicle. Unless American social mores are going to change significantly, I don't see why self driving cars would really change the fact that people like being in a car alone.

> Light rail is, by definition, light capacity transit. The theoretical 16,000 people per hour requires a “target max load” of 200 people per car on four-car light rail trains at three-minute headways for a full hour, a concept unheard of in the United States.

This is not unheard of at all. We have bigger light rail systems running smaller headways, to say nothing of very large traditional rail systems. New York City is running 600 foot trains every 2 minutes with an ultimate capacity of >60000 pphd.

Also, this article is a bit dated; we now know that Sound Transit is purchasing the Siemens S70. The identical Portland model carries 240 people per car. And while the current service plan calls for trains every four minutes in the busiest segments, the signaling system actually supports trains every 2 minutes so long as you have the vehicles. (This is not the lower limit for rail signaling systems; trains every 90s are run on many systems around the world.) Buying new trains is cheap compared to building more tracks or lanes.

> Sound Transit officials also claim that they will carry 561,000 to 695,000 unlinked daily trips by 2040 if ST3 passes. Let’s assume Sound Transit carries its highest projection of 695,000 daily trips with their estimate that most (91%) will be trips taken by existing transit riders. This means that only 62,550 will be trips taken by new transit riders.

This assumes the only utility of a transit project is new trips or new riders. This isn't true; there is also value in speeding up existing commutes. The bus gets caught up in the same highway traffic and has very high labor costs per trip; moving bus passengers to a light rail train free from traffic will increase reliability and reduce commute times. And every person on a light rail train is a person not taking up space on a road. Which isn't to say that it relieves congestion, but rather it frees up space and provides an alternative to congested roads.

It's also worth noting that Sound Transit's recent record shows that it is most likely underestimating ridership: in 2016, the brand new University Link extension had already doubled initial estimates of its first year ridership, and the line well exceeded its 2020 ridership goals in 2018. https://www.historylink.org/File/20720

> This means that under ST3, each new transit rider will cost over $1 million dollars.

It's worth noting that this figure is not qualified by how much road projects cost per road user, because this is not meant to be a comparative talking point. Roading projects are just as expensive, if not more due to higher land requirements; yet they are not scrutinized to the same degree.

If you were to even try and match half of the capacity in a road expansion, it would be prohibitively expensive. The SR 99 tunnel we just built cost $3.2B for two lanes in each direction with no exits. This is double the cost of the aforementioned University Link, which is nearly a mile longer than the road tunnel to boot. The reality of the situation is any additional capacity in the transport system is going to cost a lot of money now that the city is rapidly growing and densifying, and roads cost more because they require more land.

In a vacuum, I'm actually totally fine with either option (public transportation or cars) and not particularly married to see either one built or against either one being built and both have their utility. Personally, I think both need to be built. My main concern is really about who is going to pay for it.

Such projects really disproportionately benefits those that will be commuting into and out of Seattle and those people in Seattle that live in parts of the city where they don't have parking and are likely to live near a station.

I'm a huge proponent of people paying for those services they use and for services to be financially self sustaining.

People who take the train should fund the train. People who drive cars should fund the roads and the DMV.

Furthermore, the same argument for greater throughput of a system should also support the argument that such a system should generate greater revenue and be naturally self sustaining. But for this to be true, all calculations shouldn't be based on theoretical limits but actual predictions of how many more people will be moved per hour per direction and that needs to be compared to the revenues and the costs to figure out if the current design of the system is sustainable (a lesser more modest design might be warranted once faced with the reality of how many riders are actually expected).

> It's worth noting that this figure is not qualified by how much road projects cost per road user, because this is not meant to be a comparative talking point. Roading projects are just as expensive, if not more due to higher land requirements; yet they are not scrutinized to the same degree.

They should get the same scrutiny. One proposed system getting this scrutiny isn't an argument that neither should get the same scrutiny.

> The SR 99 tunnel we just built cost $3.2B for two lanes in each direction with no exits.

And it has tolls, but the tolls should probably be 3x higher than they currently are. Every system, roads or rail, should pay for itself. Any system that isn't priced appropriately is distorting the market and making it harder to figure out the true cost and plan effectively.

One thing I would love to see adopted in the US is a public transportation tolling system like they have in Japan where you pay for distance traveled and the cost of your commute in general.

In the interest of stating my biases, personally, I purchased a home in a part of Seattle that is unlikely to ever see much if any benefit from a subway system. I'm familiar with the geotechnical concerns where I live and the only public transportation which will ever serve my home and my neighborhood is likely to be a bus (this is not too dissimilar to the reason why Beacon Hill will also not benefit). I am, however, in favor of buses and would also like to see investment long term in smart streets that provide a foundation of an autonomous vehicle system.

Lastly, thanks for engaging in good faith discussion unlike other commenters here.

It is a statement about the bias of the linked piece though, which is quite clearly right-wing.

> One thing I would love to see adopted in the US is a public transportation tolling system like they have in Japan where you pay for distance traveled and the cost of your commute in general.

Roads also work like this in Japan. But I wouldn't call the Japanese system much better; Japan allows companies to subsidize 1000USD per month for each employee, in a manner similar to how American employers subsidize healthcare. This has the effect of making travel relatively pricey in general (because people with subsidy can afford to pay more), and also the effect of concentrating employment in major urban areas, because if you live in a small city with low transportation costs you are essentially leaving most of that 1000USD off the table.

In the West we treat travel as a public good, but it's really only an American thing that we tilt so much funding in favor of just the car.

> the only public transportation which will ever serve my home and my neighborhood is likely to be a bus (this is not too dissimilar to the reason why Beacon Hill will also not benefit).

There's nothing wrong with buses. The major problem is that Seattle has relied too much on buses; pre-COVID, public transit funds were being unspent because the ability to allocate money to transit has exceeded the capability to actually spend it for such a purpose. They literally could not find enough drivers to run the service already being funded because of how tight the employment market was.

One major reason why light rail is being pushed so heavily is because it is both more labor efficient in general (a driver can either operate a 40/60 foot bus or a 380 foot train), and because the major speed and reliability increases of the rail system will allow less vehicles to serve the same frequency. The long-term plan (at least before COVID took a sledgehammer to public finances) was to redirect bus resources from long, infrequent commuter routes to short, frequent feeder routes to Link.

Also your comment about Beacon Hill is strange, because Beacon Hill does have a light rail stop, today. Even if you're not next to it, the 36 bus runs straight through Beacon Ave every ten minutes throughout the day.