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Old 02-12-2015, 10:34 AM
 
Location: Vallejo
14,093 posts, read 16,130,435 times
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Quote:
Originally Posted by drive carephilly View Post
I think what people care about are apples to apples comparisons. You're accusing other people of fantasy but you're throwing out questionable stats about a BRT system that doesn't exist in the US or Canada (or Europe or Australia). Your TransMilenio fantasy world doesn't add up in any sense and that's why you routinely avoid responding directly to critiques of passenger counts or costs.



BART is probably more like 28,000 peak hour at this point . . . but if every train were a 10 car train then capacity is closer to 60,000 which they've probably approached for a few recent special events.



Two problems here - 1. 41,000 isn't the actual capacity of any line in the TransMilenio system. It's the capacity of half a dozen or more lines added together because they share part of a route 2. You're talking about replacing LRT with BRT except that the "hypothetical practical capacity" of LRT is similar to that of heavy rail. If it makes you feel better replace "BART" with "LA Blue Line" and give it all of the grade separation of your hypothetical North American BRT.

http://www.bart.gov/sites/default/fi...0Summary_0.pdf

It's 21,000.

As I've long held, I don't have an particular interest in arguing facts with anyone. You don't believe federal government statistics, and that's fine. Feel free to present stats that you feel are more accurate and we can have a debate on that. I won't, however, accept your opinion on reputable statistics simply because they upset you for not conforming to your bias. I also really don't have much interest in esoteric arguments about hypothetical capacities. It just doesn't interest me that much. For a car analogy, it's your grandmother needing a car to go to church and the grocery store and the two grandsons having a heated argument over whether the Lamborghini or Ferrari is the better choice. There might be a context where that's actually relevant, but it isn't relevant to the grandmother or the types of transit needs where BRT is discussed as an alternative.
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Old 02-12-2015, 10:36 AM
 
Location: Vallejo
14,093 posts, read 16,130,435 times
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Quote:
Originally Posted by urbanlife78 View Post
What caps out at around 2,000 in Portland? I am not sure what you are talking about here.
We're talking about passengers per hour per direction capacities and actual demand. Eg, BARTs actual demand is about 21,000 pphpd.

Last edited by Malloric; 02-12-2015 at 10:53 AM..
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Old 02-12-2015, 10:46 AM
nei nei won $500 in our forum's Most Engaging Poster Contest - Thirteenth Edition (Jan-Feb 2015). 

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Location: Long Island / NYC
45,992 posts, read 42,089,742 times
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Here's the capacity of a system that uses mostly light rail length trains but is entirely grade separated. For a less busy line:

It is highly likely that the new SkyTrain vehicles will be inserted into service on the busier Expo Line segments as opposed to the Evergreen Line, as it is planned that the Evergreen Line will begin service with 2-car configuration Mk II trains at 3 minute frequencies during the peak hours.

This could probably be served just as well as by BRT in the capacity sense — of course since it's part of a larger rail system and it can run driverless BRT would be dumb.

A SkyTrain segment that can be expected to feature a headway of 75 seconds (the theoretical maximum possible headway) with exclusive use of 5-car variant ART 300 trains (i.e. the segment between Columbia and Waterfront Stations) has a massive theoretical carrying capacity of 44,800 people per hour per direction (pphpd) with a 925 passenger carrying capacity of each train [61] at a 6 passengers/m2 crush-load density.

Once you're running five car trains, you're past BRT capacity. And a bus every 75 seconds is liable to be unreliable. A five car SkyTrain is more like a subway system than typical light rail though.

TransLink to order several longer SkyTrain cars in 2016-2017 | Better Surrey Rapid Transit
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Old 02-12-2015, 10:49 AM
nei nei won $500 in our forum's Most Engaging Poster Contest - Thirteenth Edition (Jan-Feb 2015). 

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Location: Long Island / NYC
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And in more detail with a map of current volumes:

https://voony.wordpress.com/2014/12/...t-requirement/
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Old 02-12-2015, 11:14 AM
 
1,478 posts, read 2,006,351 times
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Quote:
Originally Posted by Malloric View Post
Great, here we go on the hypothetical carrying capacities no one cares about. So BRT can only "hypothetically practically carry" numbers around what heavily used heavy rail systems can (BART carries about 21,000 peak inbound). The "hypothetical practical capacity" being 15,000 instead of the actual capacity being 41,000 might actually matter if anyone was talking about replacing BART with BRT. And nobody is. Meanwhile, light rail like Portland's tends to cap out at around 2,000. Seattle's Link was designed so it could be scaled up to about 5,600.
If you throw out a figure of 41,000, you better be able to show how that is applicable to a transit scenario in the US, Canada, etc. That's all I'm saying. You can't ignore the fact that they're packing people at crowd densities 50% greater than what English football grounds were supposed to be packing people into terraces with crush barriers pre-Hillsborough. If they're running expresses using extremely generous ROW, you can't ignore that either. If it can't be built here, because the system is a death trap (and it is) and the government just can't go seize a bunch of land at basically no cost and tell land owners to take a hike, then it's completely meaningless.

I'm a proponent of BRT, but throwing out fantasy numbers isn't at all helpful to the cause.

If we're going to be fair about this, we need to look at what 50 feet of ROW gets you BRT vs. LRT in terms of passenger capacity (ie, no overtaking), what 75 feet gets you (dedicated loading lane w/ overtaking) for both LRT and BRT.

We also need to consider how the characteristics of LRT and BRT affect the required specs of the platform. If we assume LRT is twice as long with twice the headway of BRT, then the platform specs change. Depending upon site area characteristics at a station, this could require greater ROW in some instances for BRT or LRT.

I completely agree with you that in certain cases, a 10K or maybe even 15K peak capacity BRT line could be better than LRT (provided BRT could handle the shared intersection issues 40-60 sec headways would introduce at that level of volume). That's the upper limit given where the density and ROW exist though. I'll also defend BRT unequivocally when we're talking about low ridership lines. A string of LRT stations that are only handling 500 passengers per hour during peak times is a waste of money.

One thing I haven't seen from a neutral third party is an explicit line by line operating cost analysis covering maintenance, fuel, depreciation, driver cost of BRT vs. the same for LRT. I've seen comments here or there and have seen studies on cost curves at various volumes, but nothing the explicitly breaks down the costs so that someone could test cost assumptions at various volumes. Anything that I've seen at this level of detail usually comes from a pro-LRT or pro-BRT source.
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Old 02-12-2015, 11:15 AM
 
Location: Portland, Oregon
46,053 posts, read 29,590,013 times
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Quote:
Originally Posted by Malloric View Post
We're talking about passengers per hour per direction capacities and actual demand. Eg, BARTs actual demand is about 21,000 pphpd.
Ah, so you are trying to compare apples to oranges. Currently the MAX runs on 15 minutes schedules with 4 trains an hour per line, per direction, and can carry a max of 268 people, which comes to just over 2100 people. To match that number with Portland buses, you would have to run 41 buses per hour, per line, per direction to match what four light rail trains can do per hour in Portland.

Now how much does it cost to pay 41 drivers compared to 4, and how much does it cost to fuel 41 buses compared to providing electricity for rail?
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Old 02-12-2015, 11:16 AM
nei nei won $500 in our forum's Most Engaging Poster Contest - Thirteenth Edition (Jan-Feb 2015). 

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Location: Long Island / NYC
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Though from the rider's perspective transit that arrives every two minutes is much more convenient than 15 minutes. Frequency matters a great deal in the appeal of transit.
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Old 02-12-2015, 11:20 AM
nei nei won $500 in our forum's Most Engaging Poster Contest - Thirteenth Edition (Jan-Feb 2015). 

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Location: Long Island / NYC
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Quote:
Originally Posted by Chicago76 View Post
If you throw out a figure of 41,000, you better be able to show how that is applicable to a transit scenario in the US, Canada, etc. That's all I'm saying. You can't ignore the fact that they're packing people at crowd densities 50% greater than what English football grounds were supposed to be packing people into terraces with crush barriers pre-Hillsborough. If they're running expresses using extremely generous ROW, you can't ignore that either. If it can't be built here, because the system is a death trap (and it is) and the government just can't go seize a bunch of land at basically no cost and tell land owners to take a hike, then it's completely meaningless.
What's the crowd density that actually is?

Quote:
I completely agree with you that in certain cases, a 10K or maybe even 15K peak capacity BRT line could be better than LRT (provided BRT could handle the shared intersection issues 40-60 sec headways would introduce at that level of volume). That's the upper limit given where the density and ROW exist though. I'll also defend BRT unequivocally when we're talking about low ridership lines. A string of LRT stations that are only handling 500 passengers per hour during peak times is a waste of money.
Except that limit is moot for the US, since few if any US light rail systems reach that limit.
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Old 02-12-2015, 11:26 AM
 
Location: Portland, Oregon
46,053 posts, read 29,590,013 times
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Quote:
Originally Posted by nei View Post
Though from the rider's perspective transit that arrives every two minutes is much more convenient than 15 minutes. Frequency matters a great deal in the appeal of transit.
That all depends on where one lives, if one lives on a line serviced by one train, it is every 15 minutes, but if one lives along the eastside corridor portion that has 3 train lines, that is a train every 5 minutes.

Of course Portland has two structural problems it will need to deal with. The aging Steel Bridge, and the Pioneer Courthouse Square intersection.
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Old 02-12-2015, 12:00 PM
 
Location: Vallejo
14,093 posts, read 16,130,435 times
Reputation: 12690
Quote:
Originally Posted by Chicago76 View Post
If you throw out a figure of 41,000, you better be able to show how that is applicable to a transit scenario in the US, Canada, etc. That's all I'm saying. You can't ignore the fact that they're packing people at crowd densities 50% greater than what English football grounds were supposed to be packing people into terraces with crush barriers pre-Hillsborough. If they're running expresses using extremely generous ROW, you can't ignore that either. If it can't be built here, because the system is a death trap (and it is) and the government just can't go seize a bunch of land at basically no cost and tell land owners to take a hike, then it's completely meaningless.

I'm a proponent of BRT, but throwing out fantasy numbers isn't at all helpful to the cause.

If we're going to be fair about this, we need to look at what 50 feet of ROW gets you BRT vs. LRT in terms of passenger capacity (ie, no overtaking), what 75 feet gets you (dedicated loading lane w/ overtaking) for both LRT and BRT.

We also need to consider how the characteristics of LRT and BRT affect the required specs of the platform. If we assume LRT is twice as long with twice the headway of BRT, then the platform specs change. Depending upon site area characteristics at a station, this could require greater ROW in some instances for BRT or LRT.

I completely agree with you that in certain cases, a 10K or maybe even 15K peak capacity BRT line could be better than LRT (provided BRT could handle the shared intersection issues 40-60 sec headways would introduce at that level of volume). That's the upper limit given where the density and ROW exist though. I'll also defend BRT unequivocally when we're talking about low ridership lines. A string of LRT stations that are only handling 500 passengers per hour during peak times is a waste of money.

One thing I haven't seen from a neutral third party is an explicit line by line operating cost analysis covering maintenance, fuel, depreciation, driver cost of BRT vs. the same for LRT. I've seen comments here or there and have seen studies on cost curves at various volumes, but nothing the explicitly breaks down the costs so that someone could test cost assumptions at various volumes. Anything that I've seen at this level of detail usually comes from a pro-LRT or pro-BRT source.
Why?

Source link clearly says 41,000 doesn't translate to the US context. As I said, all I can do is present the facts and analysis. I can't force people to read them. I have no interest in reinventing the wheel nor an ability to improve upon it. The document speaks for itself. I pointed out what federal government's analysis on the subject said. I'm really done at that point. It speaks for itself. If people have an issue with the analysis because it challenges their perceptions, that's great. If they react by digging their heels into the ground and throwing a temper tantrum... so be it. I don't see why that has anything to do with why I have to back up something I have nothing to do with. Take it up with them.

Moreover, it's not really my point. Whether or not it's 15k or 41k I frankly don't care about. Seattle LINK was designed to be expandable up to about 5,600. Beyond that, it needs to be completely redesigned. The point is very simple. BRT can meet those capacities easily. Build what works best. If LRT on its merits is the better solution for a particular problem, then build LRT. No one is saying that just because BRT is easily capable of handling the actual demands it's therefore better. Well, Nei said they said that but that's because he was mistaken, probably due to reading a soundbite out of context. The context is clearly capacity within the parameters of actual demand of US systems.
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