New info on the Southwest Corridor options

Lately, the Powell/Division project has been getting much of the press, with significant public outreach in advance of next week’s Steering Committee meeting.  But the Southwest Corridor project–a project that is on a far longer timetable–has been making some advances as well.   This past week, three new documents were published by the project team:

While there are many details to be worked out, one of the key sets of decisions to be made–and this may not be made for a while, as the DEIS process may include multiple options for analysis–are the mode (BRT or light rail) and the various tunneling options.

More after the jump.

The options

If light rail is chosen as the alignment, then use of tunnels to serve destinations that are more difficult to reach by surface transit becomes possible. Running combustion-powered buses in tunnels with stations is more problematic due to ventilation issues–if BRT is chosen, all but one of the tunnel options are off the table.

Between Portland and Hillsdale, there are three possible LRT routes:

  • Surface LRT along Barbur. (Downtown, the route might use Barbur or Naito Parkway to approach downtown, but we’ll ignore that).
  • A deep-bore tunnel from downtown to SW Bertha Boulevard, south of Hillsdale and west of Burlingame. Thus tunnel would have two stations–one at Hillsdale and one at Marquam Hill/OHSU, and an exit portal station at 13th and Barbur (near the Burlingame Fred Meyer).
  • Surface LRT along Barbur to Capital Highway, then a shorter “cut-and-cover” tunnel serving Hillsdale, with one underground station at Sunset and Capital, and also an exit portal in the vicinity of SW Bertha and a station at 13th and Barbur.

The options that run along Barbur rather than drilling a deep-bore tunnel all include a “pedestrian/bike connector” to the Marquam Hill campus:  Various different options were mentioned (elevator, surface escalator, as well as ramps/stairs) in the report.

An earlier proposal for a “short” tunnel under OHSU is no longer on the table.

In the vicinity of PCC-Sylvania, two LRT options are available:

  • Surface LRT along Barbur, with no direct connection to the PCC campus.
  • A cut-and-cover tunnel heading south along 53rd, under the campus, then emerging west of PCC near Lesser Road.

If BRT is chosen, then there are two choices of interest to this article:

  • A surface alignment along Barbur, bypassing Hillsdale.
  • A cut-and-cover tunnel serving Hillsdale, on the same (or similar) alignment as the LRT option.

There are also BRT options to directly serve PCC-Sylvania, but for BRT these are surface routes rather than tunnels.

The Numbers

The interesting part of the recent set of documents is early cost, time, and ridership projections for each of the different options. As the project is still in early planning stages, these numbers should probably be viewed as optimistic and taken with a grain of salt (they also exclude things like finance charges, costs that are included into the quoted final price tags of capital projects such as PMLR), but they are interesting to see; note that data for all of the different options is not available.

Mode/Alignment New Trips Line Ridership Travel Time Por-Tualatin Cost (est)
BRT, surface $750M-$1.2B
BRT, Hillsdale tunnel
LRT, surface 22600 36900 30
LRT, Hillsdale tunnel 21700 35500 33
LRT, deep-bore tunnel 23300 45500 27
LRT, PCC tunnel 23500 38400 31
LRT, Hillsdale + PCC tunnels 22600 3700 34 $1.9B-$2.4B
LRT, deep bore + PCC tunnels 24200 47000 28 $2.8B-$3.2B

It would be interesting to know, of course, what the estimate is for a surface LRT route is, and to see cost estimates for the various tunnel options broken out separately.

A few things stand out:

  • The Hillsdale-only tunnels seem to have a negative impact on both ridership and travel time, due to the surface routes.  The slower trip is explained by an additional station at Hillsdale, and likely by some of the tight turns involved in the tunnel alignment (in order to stay under public rights of way), but the slightly lower ridership numbers are a bit interesting, given that Hillsdale is a transit-friendly neighborhood.   The only thing that comes to mind is that the slower overall trip time will cause fewer riders further out to use the line.   (A BRT option might have an advantage if a Hillsdale-only tunnel is used; as buses can corner far better than trains).
  • Not shown in the above table, but early forecasts of line capacity are peak frequencies of 8 trains per hour for LRT (7.5 minute headways), and 20 buses per hour (3 minute headways) for BRT.  It is noted that at that frequency, traffic impacts might prevent BRT from enjoying full signal priority at crossings.
  • If the deep-bore tunnel is not done–and this is my opinion at this point–it appears that the Naito alignment has a lot more to recommend it than the Barbur alignment, as it affords the ability to work on the reconstruction of South Portland and removal of the expressway remnant that is Naito between Lincoln and Barbur.  The main difficulty is that Gibbs and Naito is 500′ further away from OHSU than Gibbs and Barbur.  But if planners can get creative with a connector option–say a tunnel and elevator, or a surface escalator–this could work.
  • If the deep bore tunnel option is used, TriMet expects that local bus trips to OHSU would drop to less than a quarter of what they are now, while total transit trips to/from OHSU would rise nearly 25%–in this scenario, many local bus trips to the campus would be eliminated, and riders on these lines (or on parallel lines in the case of the many express routes which would no longer make sense) would instead transfer to LRT.  In the case of a Barbur alignment, local bus trips up Pill Hill would drop by about half, with LRT/BRT and/or local bus to the pedestrian connector making up the difference; overall trips would rise by about 12% or so.  (In both cases, it is anticipated that use of the Portland AerialTram would decrease–with some trips replaced by walking once it becomes possible, and some Streetcar-Tram trips being replaced with LRT or BRT).
  • The PCC tunnel does add quite a bit more positive transit value.  The alignment of such a thing appears to be less tricky, thus travel time is not impacted as greatly.

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