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Danny

Great post!

I think the chokepoint example also explains why the XBL on the lincoln tunnel has provided such high capacity from bus transit, considering that it is one of the fastest ways into Manhatten given the low capacity of all the river crossings.

Jason

"On the west side of the hill, there's just one path, which is to go through the narrow space between the hill and Puget Sound (the water body on the left of this image) then north and across the Ship Canal on a single bridge."

The "narrow space" is actually between the hill and Magnolia, not the Sound. The corridor is known as Interbay and the arterial is 15th Avenue. Your point about the chokepoint still holds, of course.

Cascadian

Westlake Ave (on the east side of Queen Anne Hill and the west side of Lake Union) and then the Fremont Bridge provide another route than the one you described (Interbay and the Ballard Bridge). Both get you around the hill and across the Ship Canal. There's also the Aurora Bridge (Highway 99) that takes a much higher route on the east side of the hill.

I guess your point might be that these two routes don't go to the northwest quadrant of the city, defined by streets with the NW directional. But in practice if you're trying to get across the Ship Canal west of I-5 you might consider any of these routes. 99 tends to be used for any trips north of the canal, sometimes including parts of Ballard and Fremont. The lower bridges really only serve the local areas. And even some of the NW streets are closer to the Fremont Bridge than the Ballard Bridge.

Still, that's only three options for the NW side of the city, along with 3 others further east (I-5, University, and Montlake bridges.)

Jarrett at HumanTransit.org


You're right that corridors east of 15th NW can be fed through Fremont, which still leaves at least three (15th, 24th, and 32nd NW) that logically feed over the 15th NW bridge.    In referring to the whole NW quadrant of the city, I think I was saying that QA Hill defines chokepoints for the entire area, including the one you mention on the east side of the hill. 

Pantheon

There has been a lot of debate over what to call the decade you refer to as the "00s". I understand your reticence to use one of the proposed monikers, as the vociferous debate and entrenched views on this make the bus/rail debate look like a game of cricket.

Nonetheless, I prefer the term "noughties". It is the most linguistically accurate, but more importantly the most fun.

If you want to really go out on a limb, you could use Slate's new suggestion: the "Uh-Oh's"!

http://slate.msn.com/id/2239014/

EngineerScotty

I like the "oh-sh*ts" myself, but then I'm just decade-nt.

rhywun

I prefer "aughts" myself. Carry on.

Anandakos


Jason,

Unfortunately, the Rapid Ride bus is proposed to go up Mercer Way RIGHT into the soup of Lower Queen Anne. Gag!

There is insufficient street capacity on either Mercer Place (two lanes and narrow ones at that) or the Queen Anne, First Avenue North couplet to give a bus lane. It might be OK to turn off Elliott at Harrison to give some access to LQA and Seattle Center to the Rapid Ride; the bus would miss the worst of the mess right at Queen Anne and Mercer. But not Mercer Place/West Mercer.

Adam Parast

Jarrett I agree with you completely from a technical perspective but the simple fact is that Metro BRT solution, "RapidRide", is likely to be just about the lowest form of BRT possible. For example mid-day frequency will be 15 minutes, no new bridges will ever be built just for the bus, business access lanes are only used in the peak direction, and less than half of the stops will actually have station level amenities.

As I have written before on STB this is the problem with BRT. (http://seattletransitblog.com/2009/12/09/the-lowly-bus/)

You're talking about a level of bus based transit that will never exist in the corridor because Metro simply doesn't have the money or the vision to accomplish it.

Metro is pursuing Rapidride, I believe, mostly because it is getting free TSP from the city of seattle (via bridging the gap) and free buses from the FTA as well as money for stations and other communication expenses. If there wasn't any of this money Metro won't do it.

So while I said I agree theoretically this is another example of how BRT over-promises and under-delivers... at least in the US.

Jarrett at HumanTransit.org


Thanks, Adam.  As I said, I was not commenting on Rapid Ride in particular, just exploiting its geography to talk about the principle. 

Alon Levy

The non-US rail solution would be to terminate the trains north of the bridge and build a bus terminal right next to the station. In the German-speaking world the transfers would be timed.

BRT's main advantage in Seattle is that it can use existing streets in downtown. But even then it would need at a minimum signal priority to be able to run at decent speed. Otherwise it would get stuck behind too many signals; without signal priority, buses can be slow even when the streets are not congested.

Joshuadf

It's probably worth mentioning that the Seattle city council president wants to extend the Seattle Streetcar from South Lake Union to Fremont, probably on the east side of Queen Anne Hill (Westlake Ave N). It remains to be seen whether the rest of the council and/or the mayor will play along, though.

Casey Hildreth

Thank you Jared for writing so eloguently on the value of congestion and the importance of transit/car differentials as a factor in mode split.

I would like to point out that the geography and physical barriers in Seattle are indeed a major provider of chokepoints, but equally so are the abundance of shifting grids and multi-leg, angled intersections. As you know, these are what contribute to the chokepoints in downtown along Denny, Westlake, and south near King Street Station - not hills or waterbodies.

Capturing public space at these intersection locations - as is being done in San Francisco, New York City, and other places (Sandy Blvd in Portland, Mass and Main in Boston, H Street, et al in DC) - has already entered the U.S. urban design lexicon in a short timeframe. Expanding these open space concepts to include higher transit priority through vehicle chokepoints - think mini transit-only diagonals - should be a priority for the transportation profession as well.

anonymouse

A rail based solution would involve a transfer north of the chokepoint, trading the higher speed of rail (55 or 70 mph in a grade-separated corridor) for the delay incurred by a transfer. The high speed and reliability of the rail link would make the area around its terminus desirable for residences, and all those people making the transfer would make it a good retail location, since once they get off the train on the way home, they might as well stop by a store before getting on the bus to go home. The transfer point thus becomes a secondary center, something you don't necessarily get with just plain BRT.

Jarrett at HumanTransit.org


All true except that there would be on difference in maximum speed for rail vs bus in a grade separated corridor of this length with this station spacing.  Both would top out around 55 mph, and differences in travel time due to acceleration would be slight. 

Transfer locations make excellent retail nodes, as you point out.  This is not necessarily a sufficient reason to force a transfer if a less expensive solution provides the same mobility without that requirement.

Pantheon

To be a little more blunt, transit agencies are not developers. It gets a little tiring to hear people constantly talk about the development consequences of transit, as if the actual act of moving people around were merely a secondary consideration. It is a pollution of the mind, a pernicious and often unconscious way of thinking about transit that needs to be stamped out.

EngineerScotty


Back in the old days, transit operators built theme parks to attract riders to streetcar lines.

Now its condos. :)

TOD is useful when it's in ADDITION to (and as a result of) the act of moving existing riders and serving . Westside MAX has lots of TOD, but connecting Beaverton and Hillsboro to Portland is a worthy transit goal even if Orenco didn't turn into a pile of tacky townhouses. :) If a transit line passes through an existing brownfield or greenfield, turning it into high-density housing and getting folks out of car-dependent living isn't a bad idea.

OTOH, transit lines whose primary purpose is to serve speculative development (the SoWa streetcar extension comes to mind) are a bit more dubious.

Placemaking Institute

Higher transit use is not an input but rather an output in economic development and urban redevelopment; the benefits of great mixed-use places will outweigh all the negative externalities associated with cars and, while the effects of such developments may not be immediately felt, in a couple of generations it will be - Just like it took the pro-road/autocentric lobby a couplathree generations for their myth to be firmly inculcated. The arguments used by those who argue against our broadening our modality? Could be applied to roads at the Interstate inception in the mid-50s.

Pantheon

I don't understand what you are trying to say. What do you mean by input and output? Negative externalities? Broadening our modality? I regret that while I am relatively fluent in English, I am unfamiliar with the rather peculiar tongue of faceless committees and bureaucratic organizations.

Jarrett

Placemaking Institute isn't all that bureaucratic. He's saying that it will may take a couple of generations before sustainable urban development and transport become standard, just as it took a couple of generations for the car+sprawl model to become standard.

Placemaking Institute

Exactly, and thanks, Jarrett, for untying my purportedly rather peculiar tongue. Unless a bureaucracy can consist of one person, the Placemaking Institute is most definitely not at all in any way bureaucratic; in fact one of its intents is to satirize such faceless bureaucracies, at times by co-opting their language.

Pantheon

Rest assured that I never meant to imply you were bureaucratic, or faceless. Only that you speak in the same tongue as those who are. And I do very much appreciate satire, even if it must come at the expense of clarity.

Placemaking Institute

But I took being labeled a faceless bureaucracy as a compliment!

Nathanael

"This, friends, is one thing that rail transit doesn't do well."

Well, given
(1) that you have a fairly uncongested pre-fabricated mess of asphalt roads to spread out onto;
(2) that you don't have a pre-fabricated mess of rails to spread out onto;
(3) that a humungous pile of buses is actually sufficient capacity for the corridor and doesn't overstrain the busway.

If (3) is false, you do better to run a rail line across the bottleneck until you hit a wide-open area where you can build a major transfer center.

In suburban London, arguably (1) and (2) are both false and it may be easier to run spread-out rail services than spread-out bus services!

Nathanael

"I think the chokepoint example also explains why the XBL on the lincoln tunnel has provided such high capacity from bus transit, considering that it is one of the fastest ways into Manhatten given the low capacity of all the river crossings. "

It certainly does!

The funny thing, however, is that New York City is full of examples of doing the same thing with rail transit, even *more* efficiently. Consider the tunnels and bridges between Brooklyn and Manhattan: services spread out, merge for the tunnels, and spread out again. For a larger-scale example, consider the massive Penn Station project, connecting tunnels to New Jersey to tunnels to Long Island. Of course, failure to use through-running has lost some of the potential of that one.

These were all built in an era when there was a massive network of rails on either side of the bottleneck, in contrast to today's "massive network of overbuilt roads" present in many cities. The very same chokepoint argument demanded rail construction, not road construction.

From this we see that making use of existing infrastructure saves money. Well, duh.

Placemaking Institute

The sad thing is that many, many "natural" transportation chokepoints within this country once had railway throughputs - But they were ripped out.

Ari

@EngineerScotty

You said:

"[T]ransit lines whose primary purpose is to serve speculative development … are a bit more dubious."

Most transit lines in this country are based on lines which were built as streetcars in the early 1900s, and most streetcar companies made their money by buying land along the line and then, once there was transit, selling it at higher prices. That's speculative development. Of course, once government takes on this role, it's a bit more muddled, but there is a long (if not all-that-recent) history of transit and development.

EngineerScotty

Ari,

Certainly; OTOH with the early 20th century streetcar lines, the same entity which engaged in the real estate speculation also financed the line construction.

What many object to with TOD is the appearance of public money being used to benefit private developers. Of course, in most cases, the evidence of outright corruption is not there--there is a defensible mobility reason for putting the line where it is, and the involvement of the adjacent property owners, who can be taxed to finance construction (how much of the Portland Streetcar was funded), is often a win-win.

With some projects, though... net mobility benefits are hard to discern, or depend on the new TOD becoming an occupied and vibrant community. When this fails to occur, the line becomes--in retrospect--a boondoggle, and too many of these and people start to question the competence and honesty of the public officials responsible.

Alon Levy

Ari: yes, and those developers neglected the streetcars once they'd finished selling the land. Many lines were dying even before the National City Lines conspiracy.

On mainline railroads it was even worse. Many railroads, especially in the western US, got land for cheap by refusing to haul farmers' product, forcing them into bankruptcy. Southern Pacific engaged in so much extortion that popular writers of the late 19th century portrayed it as an octopus. This corruption then became one of the major selling points of the good roads movement: rural populists saw good roads as an alternative to the railroads, or at least a way of reaching multiple railheads, creating more competition.

EngineerScotty

I note another interesting use of chokepoints (in Hong Kong) here--essentially, since all transit services have to go through the tollbooths at bridges in tunnels in HK, the tollbooths are turned into transit centers.

Frosty

One of the biggest Seattle chokepoints not mentioned in the essay or comments is I-5 under the Convention Center and on either side of it. There are seven lanes of traffic and entrances and exits that require weaving at up to 60 mph. This area extending from the Ship Canal bridge south to the exit to I-90 is used by local traffic to get around the core of the city. Traffic backs up on the freeway and on city streets due to gridlock. It isn't clear to me that it's possible to widen the freeway under the Convetion center.

Another obstacle is southbound I-5 north of the Ship Canal. Cars unintentially slow as the grade increases over the bridge leading to backups reaching 145th St. at times.

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