Denny Way Mode Share

By JASON LI

King County Metro's Route 8 is the slowest and least reliable bus route in the entire city. That was proven this summer when hundreds of transit advocates outwalked and outdanced the bus doing the slowest things we know during our Race the L8 event. The reason for this is painfully obvious: buses are constantly stuck in the traffic towards the I-5 entrances that brings Denny Way to a standstill. Despite all of its issues, Route 8 still manages to attract 7,000 daily riders. This makes it Metro's eighth most popular route and is a testament to how vital it is as the only east-west bus route between downtown and the ship canal.

That's why the Fix the L8 campaign has been advocating for bus lanes on Denny Way for years, including writing a three part series for the Seattle Transit Blog earlier this summer. We were honored to have been able to stand and speak with City Councilmember Alexis Mercedes Rinck when she echoed our call for full-length two-way bus lanes on Denny via Better Bus Lanes campaign. She even secured majority support in City Counci for this with councilmembers Hollingsworth, Saka, Juarez, and Solomon as co-sponsors. This issue has even prompted responses from representatives in every level of local government, including County Councilmember Teresa Mosqueda and State Representative Julia Reed.

Unfortunately, SDOT seems content on allowing Route 8 buses to continue festering in traffic. It recently announced it has decided to forgo bus lanes where they are most needed along Denny Way. This decision was predicated on a fundamentally flawed traffic study, which assumed that zero drivers would switch to taking transit or switch to alternate streets after bus lanes are installed or seek alternate routes. Despite the glaring error, the study did still include some incredibly insightful data, revealing that the Route 8 riders match drivers headed to Capitol Hill on Denny Way and even outnumber drivers headed to I-5 S when combined with pedestrians as shown below.

Eastbound Denny Way mode share for May 2024. +" indicates the count is likely an underestimate

Data Analysis

Let's start by using SDOT's traffic study to set a baseline for eastbound drivers at Denny / Stewart / Yale. 341 drivers cross the Denny overpass and 396 tuning towards I-5 S between 5 PM and 6 PM. Interestingly, the 635 drivers headed west are able to meet 85% of the combined total of eastbound traffic despite only having a single lane available.

Vehicle counts at Denny / Stewart / Yale (SDOT Route 8 Study, pages 140 & 160)

For bus riders, King County Metro's data shows that there were 1,285 eastbound Route 8 riders between 3 PM and 7 PM in May 2024, the same month that SDOT's traffic counts were performed. This averages out to 321 per hour, which is just under the 341 drivers traveling east over I-5 reported by the traffic study. However, we are comparing an hourly average of bus riders between 3 and 7 PM with drivers between 5 to 6 PM, which severely underrepresents bus riders. It's unclear how much higher bus ridership is during that specific peak hour, but it would certainly be enough to result in bus riders outnumbering drivers, even if you exclude the small percentage of eastbound riders boarding east of I-5. Additionally, riders east of I-5 would still benefit from the improved reliability that a bus lane would bring to their arrival times.

The vast majority of eastbound Route 8 riders board along Denny Way (SDOT Route 8 Study, page 20)

Furthermore, there's another major factor suppressing ridership numbers for Route 8: all the people who have given up on it and just walk instead because it's so much faster and more reliable. Page 140 of SDOT's study shows that there are 346 pedestrians accessing the sidewalk crossing I-5 at the southeast corner of Denny and Stewart. It's unclear what percent continues east onto the Denny overpass, but even a conservative estimate of 50% combined with bus riders would result in people outside of a car headed east on the overpass heavily outnumbering those doing so in a car. Not only that, they would also combine to even outnumber the 396 drivers on eastbound Denny headed to I-5 S.

Pedestrian counts at Denny Way and Stewart St (SDOT Route 8 Study, page 140)

Commentary

It's obvious that there is enormous demand for Route 8, but even we were surprised to find out that Route 8 ridership outnumbers both drivers headed to Capitol Hill and drivers headed to I-5 South. This shows that a bus lane would have extensive benefits. But what about the delay that drivers would experience?

The biggest negative impact would be to drivers continuing east over I-5 to Capitol Hill. They would be caught in the same I-5 traffic on Denny Way that currently stymies buses. However, buses would now be free of that traffic, and these drivers are the ones who could most readily benefit from a fast, reliable bus. If bus lanes unlocked a modest average speed of just 7.5 mph, buses would be able to travel twice as fast as current speeds reported in SDOT's study, and travel between Seattle Center and I-5 in just 8 minutes.

Once drivers realize just how fast of a commute taking the bus would unlock, they would surely start leaving their cars at home rather than experience the same delay and frustrations bus riders deal with today. This would certainly induce massive mode shift, but SDOT's study failed to consider this and ruled out bus lanes while completely ignoring the benefits of them. Nevertheless, a bus lane would still benefit more people than it would delay even without any mode shift, which the study and SDOT failed to recognize.

But what about drivers headed onto I-5? The Yale on-ramp is so inefficient that it would still remain the bottleneck even after bus lanes are installed. This is reflected by the fact that the single westbound travel lane at Stewart can support 85% of the combined traffic from the eastbound lanes. If even a fraction of drivers switch to transit, a single eastbound lane west of Fairview could fully support all remaining eastbound car traffic. Once you combine the aforementioned mode shift to Route 8 with what that the upcoming Federal Way and cross-lake 2 Line Link extensions would bring, achieving that mode shift is more than guaranteed, and I-5 drivers would consequently only experience negligible delays.

We're not alone in this line of reasoning either. We have now found a surprising ally from the agency that is most qualified to speak on highway traffic: WSDOT. State Representative Julia Reed checked in with them and let us know that WSDOT is unconcerned" about the potential impacts a bus lane would have on I-5 and that [t]he state's ready to talk prioritizing transit on Denny."

In summary, bus lanes would not result in meaningful delay for I-5 drivers. The drivers primarily impacted would be those headed east across the Denny overpass. However, they are the ones who could most easily take advantage of that shiny new bus lane and leave their car at home to enjoy a faster commute than they have today. All this while also benefitting the massive number of existing bus riders and pedestrians that greatly outnumber both I-5 and Capitol Hill drivers. Bus lanes are an obvious choice on Denny Way. SDOT needs to install them immediately, and stop punishing the plurality of people on Denny Way who are travelling in a climate- and community-friendly way.