When SR 99 closed for three weeks, we knew people were relying on Metro, Seattle and the Washington State Department of Transportation to keep them moving.

Review of the West Seattle Water Taxi showed ridership tripled to 30,915 compared to 9,826 in 2018, thanks in part to more frequency and reliability of an added boat, twice as many shuttles and free parking in West Seattle.

Ridership samples also show that after an apparent dip during Week 2 (likely due to lower ridership demand on the Martin Luther King Jr. holiday), Metro finished with higher estimated bus ridership on the 41 routes that were directly affected by the closure, compared to January 2018 baselines. Transit use was up according to Sound Transit also: During the viaduct closure Link light rail ridership was up 14 percent and Sounder ridership was up 4 percent. Between those two services they had more than 15,000 new people using transit.

Clearly, travelers changed their habits – avoiding optional trips, shifting from driving to transit, flexing work schedules or telecommuting, carpooling and taking time off. Metro had 20 buses on standby for when traffic backed up on critical routes and doubled the West Seattle water taxi sailing frequency, adding shuttles and parking at Pier 2 in West Seattle.

Across the 41 routes, Metro collected ridership samples on weekday trips Jan. 14-18, Jan. 21-25 and Jan. 28-Feb. 1. The SR 99 tunnel opened Feb. 4 (but we are still collecting ridership as the travel patterns will evolve for several more months.)

What did we find?

Based on samples and extrapolations, we’ve produced an unofficial ridership tally that helps us understand how ridership might have shifted during the SR 99 closure period. Metro typically provides more than 400,000 bus rides to the region each day across more than 200 bus routes, upwards of 122 million rides per year.

bar chart of ridership estimate totals compared to 2018 january baseline. 131k. Week 1 was 134,842 +2.4%; Week 2 was 124,426 for -5.5%; week 3 was 137,915 for +4.7%

 

King County Metro bus service on 41 selected affected routes
Timeframe Average Weekday Daily Ridership Change from Baseline
Baseline 2018 129,918
SR 99 closure Week 1 131,422 +1.2%
SR 99 closure Week 2 121,556 -6.4%
SR 99 closure Week 3 134,844 +3.8%

 King County Metro bus service
(41 selected affected routes) & Water Taxi service
Timeframe Average Weekday Daily Ridership Change from Baseline
Baseline January 2018 131,675
SR 99 closure Week 1 134,842 +2.4%
SR 99 closure Week 2 124,426 -5.5%
SR 99 closure Week 3 137,915 +4.7%

 

It’s too early to say how overall annual ridership will be affected. The recent snowstorm reduced ridership for about two weeks. We’re pleased to see that, based on these extrapolations and smooth traffic overall, transit played a major role in keeping people moving during the biggest closure of a highway in Puget Sound history.

How did we estimate ridership?

Metro has automatic passenger counters on about 50 percent of its fleet. To calculate ridership estimates, it usually takes months of observations and rotating the fleet around King County in order to produce a reliable estimate of ridership – both for totals and daily averages by route.

But during the SR 99 closure Metro collected samples on the 41 most affected routes and compiled sampling data weekly.

Math part: We tallied trips and riders to establish a “January 2018 average” for each of the 41 routes. We then observed as many trips as we were able to using buses with passenger counters. We calculated an average (sometimes plugging in data on an unobserved trip by using a data from the previous month) and multiplied it by the number of scheduled trips and extrapolated an unofficial average daily total. We also calculated average “standby” bus ridership for the extra buses that were temporarily added to the schedule to compensate for traffic congestion.

January 2018 Week 1 Week 2 Week 3
Route Corridor Sched. Trips Summary of Ridership Sched. Trips Summary of Ridership Sched. Trips Summary of Ridership Sched. Trips Summary of Ridership
15 15th/Elliott 22 1,509 22 1,448 22 1,193 23 1,517
17 15th/Elliott 17 1,159 19 1,227 19 1,025 19 1,250
18 15th/Elliott 16 1,120 17 1,187 17 865 17 1,142
19 15th/Elliott 11 347 11 370 11 317 11 341
24 15th/Elliott 81 2,310 82 2,338 82 2,118 82 2,287
33 15th/Elliott 79 2,177 79 2,122 79 1,871 79 2,119
D Line 15th/Elliott 230 14,465 234 14,371 240 13,495 234 14,521
5 Aurora 176 8,419 186 8,573 186 7,857 187 8,421
26 Aurora 87 3,005 87 2,984 87 2,599 87 3,185
28 Aurora 98 3,316 101 3,436 101 3,070 101 3,514
E Line Aurora 230 17,472 259 16,816 259 16,257 258 17,667
62 Dexter 162 7,629 163 8,431 163 7,884 163 8,412
101 I-5 south of downtown 97 4,766 122 4,689 121 4,488 121 5,023
102 I-5 south of downtown 14 1,013 22  1,454 22 1,292 22 1,479
143 I-5 south of downtown 14 583 14 543 14 486 14 543
150 I-5 south of downtown 130 6,068 132  6,163 132 5,728 133 6,578
157 I-5 south of downtown 7 209 7 242 7 194 7 217
158 I-5 south of downtown 12 564 12 540 12 540 12 566
159 I-5 south of downtown 9 367 9 337 9 251 9 351
177 I-5 south of downtown 18 566 18 489 18 360 18 513
178 I-5 south of downtown 15 454 15 417 15 345 15 461
179 I-5 south of downtown 19 811 19 692 19 599 19 746
190 I-5 south of downtown 15 405 15 391 15 344 15 380
192 I-5 south of downtown 8 134 8 120 8 121 8 148
193 I-5 south of downtown 14 487 14 453 14  427 14 466
21 Viaduct/1st/
4th		 157 4,885 162 5,040 162 4,722 164 5,142
37 Viaduct/1st/
4th		 7 183 8 171 8 162 8 180
55 Viaduct/1st/
4th		 22 1,081 23 844 23 678 23 903
56 Viaduct/1st/
4th		 17 821 19 666 19 727 19 822
57 Viaduct/1st/
4th		 8 424 10 409 10 423 10 472
113 Viaduct/1st/
4th		 11 242 11 227 11 213 11 241
116 Viaduct/1st/
4th		 17 635 17 530 17 466 17 624
120 Viaduct/1st/
4th		 164 8,430 186 8,442 187 7,989 185 8,832
121 Viaduct/1st/
4th		 37 992 37 802 37 745 37 927
122 Viaduct/1st/
4th		 14 508 14 411 14 365 14 431
123 Viaduct/1st/
4th		 9 355 9 273 9 262 9 282
125 Viaduct/1st/
4th		 78 1,694 78 1,479 78 1,433 78 1,457
131 Viaduct/1st/
4th		 81 3,125 82 3,443 83 3,044 81 3,333
132 Viaduct/1st/
4th		 80 2,793 80 2,965 81 2,762 81 2,941
C Line Viaduct/1st/
4th		 238 12,214 255 12,694 255 12,069 254 13,434
WT – Vashon Water Taxi 12 1,003 12 1,128 12 964 12 1,088
WT – West Seattle Water Taxi 24 754 58 2,291 58 1,906 58 1,983
40 Westlake 177 12,180 192 13,191 192 11,773 193 12,974
*Total
estimates
(average
figures
were
rounded
to the
nearest
whole
number)		 2,734 131,674 2,920 134,839 2,928 124,429 2,922 137,913