'The three ring circus'

A JOLT News Investigative Series

 
It was 2016 and Tumwater had a problem: too many vehicles were trying to pass through the intersection at Capitol Boulevard SE and Trosper Road SW. If left unaddressed, state regulations adopted as a result of the consequential 1990 Growth Management Act would bar the city from permitting new development in the area.

Had this happened, the city’s Capitol Boulevard Corridor Plan, an ambitious plan to entirely redefine the character of Capitol Boulevard from The Brewery District through to the airport, would be in jeopardy. Improving the throughput of Capitol and Trosper junction was essential.

Artist rendering of Tumwater's proposed Capitol Boulevard Corridor Plan

Courtesy City of Tumwater

A failing intersection meant “chronic congestion is predictable and extends well beyond a ‘peak 15 minutes’ at the end of the workday.” And indeed, regular 30 second delays were recorded at Capitol and Trosper in 2015 and, based on anticipated population growth, were expected to extend to almost two minutes by 2040. 

The single most important intersection in Tumwater is the one at Capitol and Trosper. The intersection’s two streets are each part of the National Highways System, federally designated arterials deemed “Important to the nation's economy, defense and mobility.” Yet, up to 60 cars were queuing at peak times, with expectations that things would get far worse.

The inability of the current design to efficiently move vehicles through the intersection annoyed residents and risked triggering restrictive enforcement provisions of the Growth Management Act. The GMA’s “concurrency” requirement meant the city had to plan to relieve the traffic congestion that already existed before any new development could be allowed. Something had to be done to improve traffic flow through the intersection. But what? 

Responsibility for addressing the mess fell to the Engineering Department within the City of Tumwater. As planning work began on the intersection’s redesign, it was quickly determined that a major impediment to fixing the intersection was that it was too close to the adjacent freeway interchange to and from northbound Interstate 5 (while it’s hard to recall, those entrance and exit ramps used to terminate directly onto Trosper Road, adjacent to the freeway overpass).

The problem was that cars traveling eastbound on Trosper Road didn’t have enough space to queue up for a complete signal light cycle at the intersection with Capitol Boulevard. As a result, cars would block the box at the freeway interchange, which worsened the overall traffic flow in the area. Fundamentally, it wasn’t possible to fix congestion at Capitol Boulevard and Trosper Road without additionally reconfiguring the adjacent intersection at Trosper Road and Interstate 5. And with that realization, a project to rebuild one intersection became a project to rebuild two. 

One of the most creative changes in the project came when it was realized that a new road (and intersection) could be added, which became known as 6th Avenue SW. This short street parallels Interstate 5 on its east side, running between Trosper Road to the north and Lee Street to the south. In the middle of this street is what would become the third intersection to be included in the project — a roundabout, of course — which is where the freeway ramps now terminate. The addition of 6th Avenue created an alternative traffic path that would completely reroute some traffic from needing to traverse the Capitol Boulevard and Trosper Road intersection at all. 

To configure the new traffic plan, sophisticated traffic modeling software was used to test how different traffic configurations would impact traffic flows. Scores of scenarios were tested, even one that necessitated building a new — and quite expensive — new freeway overpass. In the end the option the city selected was three, multi-lane roundabouts. 

These closely linked roundabouts have been called what JOLT reader SecondOtter humorously dubbed "The three ring circus." Clark Griswold would have hated them.

Unfortuneately, roadway construction at this scale doesn’t come cheap. The city had to demolish the Key Bank branch at Capitol and Trosper and an existing eight-unit apartment building atop what would become 6th Avenue. The city even had to subsidize the rent differential for residents forced to move to more expensive housing. Roundabouts take up more space than a signalized intersection, and that land had to be bought, too. Just purchasing the properties needed for the project cost about $5 million. 

But, of course, the costliest expenses for the project were for the engineering work that preceded construction, and the cost of labor and materials for the actual work itself. And Tumwater’s timing couldn’t have been worse.

According to the Federal Highway Administration, the overall cost for highway construction projects has exploded this decade: the National Highway Construction Cost Index rose 88% over the entirety of the project. All told, the complete Capitol Boulevard and Trosper Road Intersection Reconfiguration project came in at just over $20 million. A total of $10,768,988.44 was paid by the city, almost $1,000 for each of the city’s 10,929 households.

In tomorrow’s segment: Epilogue: The Growth Management Act as viewed from one small city’s intersection 

Read previous installments in this series on The JOLT News website: 

Part 1: The Creation of Washington’s Growth Management Act 
Part 2: How the GMA Impacts Local Government Transportation Initiatives
Part 3: Clark Griswold’s nightmare: How Roundabouts Became Traffic Engineers’ Preferred Solution