Justification for Smarter Transit’s Analysis of 2050 Rail Transit Mode Share for the Central Puget Sound Region

By Smarter Transit Co-Chair, John Niles
Prepared August 2022; Amended June 12, 2024

Smarter Transit has calculated the officially modeled travel mode shares for 2050 from published data produced by Puget Sound Regional Council and Sound Transit.  Finding the future travel share for the controversial rail programs in the Puget Sound region requires special calculations from diverse published numbers.

The number of modeled central Puget Sound work trips and non-work daily trips are revealed in Appendix H of the PSRC Regional Transportation Plan (RTP) for 2050 in Table 14 and Table 19 respectively.  Here are the trip counts from the Regional row on those two tables.

Appendix H of the RTP is at https://www.psrc.org/media/5942

Daily Trips Drove Alone Shared Ride Transit Walk & Bike
Work Trips 2,049,300 537,400 469,800 696,800
Non-Work Trips 6,677,500 8,100,100 1,463,100 4,064,400

Total trips in a day are the sum of all eight entries in the table above, 24,058,400 daily trips.

Summing across both of the two trip types, we obtain:

Daily Trips Drove Alone Shared Ride Transit Walk & Bike
Total Trips 8,726,800 8,637,500 1,932,900 4,761,200
Mode Share 36.3% 35.9% 8.0% 19.8%
SEIS Reported 55% 14% 13% 18%

The SEIS (Supplemental Environmental Impact Statement) reporting different numbers is at https://www.psrc.org/media/5945.  Discrepancy has not been addressed by Smarter Transit.

We rounded these to percentages. However, we did further work to subdivide the transit share into all rail, including light rail, and the combined modes of buses & ferries. 

But first, ferries are significant transit. PSRC published the following statement in the RTP Chapter One document on page 53, “Ferries maintain around 3% of all public transit boardings in 2050, similar to 2018.” Document is at https://www.psrc.org/media/5934.

In Table 3 of Appendix H of the RTP, transit boardings in 2050, not including ferries, are shown as

Transit Agency 2050 annual boardings Fraction of total
Sound Transit 278,515,000 37.3%
All other bus agencies 461,825,000 61.8%
Other, not explained 6,346,000 0.8%
Total 746,686,000 100%

We use the transit agency shares of annual boardings reported by PSRC and apply them to daily transit trips also reported by PSRC.

We ignore the missing 0.8% as unexplained and trivial.  If ferries are 3% of all transit boardings, and are not included in this table, then we can compute that 2050 ferry boardings F are found in the formula F/(746,686,000+F)=3% then F = 23,093,000 and ups the transit total to 769,779,000 but reduced to 763,432,000 by the unexplained 6,346,000.

Now to compute light rail boardings as a fraction of Sound Transit boardings, we are going to need the part of ST’s ridership that is aboard light rail, a topic not covered by PSRC.  For this we turn to the 2022 Sound Transit budget document which on page 6 shows “Ridership by Mode 2017-2046.”  This chart is in the ST document at https://www.soundtransit.org/sites/default/files/documents/2022-financial-plan-proposed-budget-book.pdf pg. 6.

We take by visual observation from this chart from the largest blue bar representing Link light rail that this mode’s ridership fraction of all Sound Transit ridership in the late 2040s is expected by that agency to be 160 million divided by 180 million, or 88.9%, which when multiplied by PSRC’s annual Sound Transit boarding metric for 2050 of 278,515,000 yields 247,569,000 light rail boardings.  The same chart by visual observation of the top of the same most right-hand column shows the remaining 11.1% of ST ridership is splitting the remaining 20 million in fractions of about 40% to Commuter rail, 40% to the new Stride Regional BRT, and 20% to Tacoma Link streetcar. Regional Express buses are apparently extinguished in favor of light rail. We than apply these fractions to the daily boarding residual – all but Link Light Rail — for Sound Transit from above, 278,515,000 minus 247,569,000 = 30,946,000

Combining all the above yields these boarding counts and percentages for 2050:

Transit Agency 2050 annual boardings Fraction of daily transit trips in each mode Fraction of all daily trips including all modes
Sound Transit Link Light Rail 247,569,000 32% 2.56%
ST Tacoma Link 6,189,000 1% .08%
ST Sounder Commuter Rail 12,378,000 2% .16%
ST Stride BRT bus 12,378,000 2% .16%
All other bus agencies 461,825,000 60% 4.80%
Ferries of all agencies 23,093,000 3% .24%
Total 763,432,000 100% 8%

Column two is the fractional composition of the first column, adding to 100%. The third column is the second column times 8.0% which is the mode share for transit from the first table above, copied from the PSRC Regional Transit Plan, Appendix H and it adds to 8%.  For example, in the first row, 8% times 32% = 2.56%. The fraction that applies annually is assumed to apply every day.

We see in the right-hand column that all the various transit modes add up to the 8% which is the fraction of trips that are aboard transit in 2050, according to Sound Transit’s modeling described above.

To roll up the numbers to eliminate small fractional shares, Smarter Transit combines the first three rows in the above table into All Rail and the bottom three into Buses & Ferries.

Transit Mode Categories Fraction of total transit trips Fraction of total daily trips
Light Rail and all other rail 35% 3%
Buses and Ferries 65% 5%
All Transit Modes 100% 8%

Note that “light rail” rounds up in the more detailed table to 3% share in 2050, but also at the same time, “all rail” rounds down to 3%, because all the other rail combined – streetcars and commuter rail — amount to less than 1%. There is a tiny sliver of ridership on Seattle streetcars that also fits within the 3% overall mode share for ”all rail.”

Comment:

Sound Transit and PSRC would probably respond to the shockingly low three percent trip mode share for all rail in the 2050 region by pointing out that rail stations are planned to attract more residential and commercial development, and that a hoped for pattern of dense development will stimulate growth in walking and cycling (20% share) instead of driving (36% SOV and 36% with passengers adding to 72% share).

The overall theory being pursued by PSRC is that more and more people will choose walking and cycling over driving if they live within a mile or two of a transit station. Active travel modes will be used to reach stores and jobs near the station, not just to board a train. More walking and cycling within zones of transit-oriented development is considered to be as important as rail ridership, which is now de-emphasized by transit agencies across the country because of changes in travel habits that emerged during and following the pandemic.

For more information please see Smarter Transit’s Promises vs. Reality Power Point. Specifically slides 15 and 16.