I want to absolutely dispel the misconceptions some seem to have about Link’s capacity. In fact, I want to challenge the assumptions that go along with it being labeled “light rail” at all. While there are no hard and fast distinctions between light rail, heavy rail, and other terms such as “metro”, they each carry with them our personal experience and prejudices.
When I think of light rail, I tend to think of two car trains, often in street right of way. There are a lot of examples of this. Portland is limited to two car trains, and runs in the street in downtown. Salt Lake City is similar, I believe, and Phoenix looks like it has only one car platforms! Denver has been two car for a long time, and is now changing that. These systems carry a lot of people – but nowhere near as many as, say, a Paris metro line.
Different parts of Link will have different needs, but all parts of Link will be able to accomodate four car trains. Each car has 74 seats, with a comfortable capacity of double that, and a maximum capacity of 200. When we start running, we won’t be filling that up – we’ll start with two car trains, and add more as they get full.
At first, Central Link will run as often as every six minutes during peak times – so with two car trains, that’s 400 per train times ten trains an hour, or 4000 people per hour per direction (pphpd). That’s more than most bus lines do in a day – in an hour. That’s the maximum capacity of many light rail systems, in total.
This is where Link is just a little different.
When University Link opens, we’ll already need three car trains during some times of day – and we’ll likely run them more often between downtown and the UW, maybe four minutes instead of six. Three car trains every four minutes takes that 4,000 pphpd and kicks it up to 600 per train, 15 trains per hour – or 9,000 pphpd. There are very few light rail systems that can do that – but quite a few metros start there in capacity.
So how about ST2? Initially, Link will run in a few overlapping segments, for service as often as every three minutes downtown. By then we’ll be at four car trains quite a bit of the day – so 800, 20 times an hour, 16,000 pphpd. That’s not light rail territory.
In ST3, with extensions to Everett, Tacoma, and Redmond, the main line will cap out at service every two minutes – but there are other changes that can be made to increase capacity even a little farther. With just the trains we have, that’s 800 people on 30 trains an hour, or 24,000 pphpd. We can also later use cars with cabs at one end instead of both*, so we don’t have a bunch of cabs in the middle of the train taking up space. That could get that 800 up to 850 or 900, and if we went a bit further and used a single vehicle the full 120m length of the platforms, it could look more like 1000 or even 1200. You can do other things, too, like taking out some seats for more standing room as they do in Japan, although I can’t imagine we ever will on this line.
These are not light rail numbers. They’re not full metro numbers – our platforms are only half as long as many New York City subway platforms – but we’re also not going to be the Big Apple anytime soon. 24,000pphpd could serve this city for a hundred years – and it’s well over light rail volumes – so I like to call Link a light metro.
By the way, just to compare – a lane of highway typically carries about 2000-2200 vehicles per hour, each with some average a bit over 1 person. 1.2 is a typical estimate during commute times. Building this system is the equivalent of getting a long term benefit of twenty more lanes of highway from Northgate to downtown (ten each way), and a bit less than that in the outskirts (just because we won’t run trains at these frequencies all the way to Redmond and Lynnwood – there isn’t demand).
The next time I hear “we should have built a subway”, I am going to link that person to this post. We’re pretty much getting one – it’s more than enough to meet our needs for a century in the corridors where we’re building it.
*These are little ASCII trains to show what I mentioned above. The dashes each represent roughly 50 people, and the angled brackets are cabs. The square brackets are cabless ends. The first one is what we can do with the trains we have. The second is how Portland is getting a bit more space, third is what we could do with trains like Dallas (DART), and fourth is what’s possible with the line we’re building, if we need more capacity in 70 or 80 years.