Transportation study indicates I-5 changes could help
During a presentation to the Wilsonville City Council addressing traffic issues along I-5 and potential solutions, Wilsonville City Manager Bryan Cosgrove quipped: "You can't build your way out of congestion."
But, according to a recent study produced by the City of Wilsonville and the Oregon Department of Transportation (ODOT), construction could at least patch up the swelling bruise.
At the meeting March 5, Wilsonville Community Development Director Nancy Kraushaar informed the City Council about the I-5 Boone Bridge Auxiliary Lane Study's findings. The study assessed existing traffic phenomena in the I-5 bottleneck from Exit 283 to Exit 282A, projections through 2040 and options for addressing traffic issues.
Kraushaar identified three options for quelling traffic in the bottleneck and provided alarming data about the increasingly congested stretch from the Wilsonville Road interchange (Exit 283) to the Canby/Hubbard/Highway 551 interchange (Exit 282A).
Option A would add a ramp-to-ramp lane between the Wilsonville on-ramp and the Charbonneau exit (282B); option B would extend the ramp-to-ramp lane further, from the Wilsonville ramp to the Canby-Hubbard exit and option C would add a second I-5 turn lane to the Canby-Hubbard/551 Highway exit off-ramp to go along with the extra lane from the Wilsonville Road exit to the Canby-Hubbard exit.
According to the study's 2040 projections, the worst traffic in an average day would flow over 20 miles per hour faster if any of the three options are implemented than if no improvements are made and almost 10 miles per hour faster under option C than option B or A. Also, without changes, 79 vehicles would squeeze into a mile-long stretch of a lane by 2040 while option C would diminish that number to 35.
The study group recommends Option C because, according to Kraushaar, it would reduce congestion, resolve weaving conflicts, improve commuter reliability and decrease accidents by 40-60 percent while increasing the construction cost by less than
10 percent, among other reasons.
"It has the most benefit from a level of service and volume capacity standpoint and those are the primary performance measures that ODOT uses to evaluate highway capacity," Kraushaar said.
"We definitely felt like we should recommend C because you're getting much more bang for your buck."
The Oregon Transportation Commission would ultimately determine I-5 changes as well as whether to add seismic upgrades to Boone Bridge, which Kraushaar says would be much more costly than lane changes, but Wilsonville City Council could pass a resolution recommending a proposal to the
Before providing councilors with a recommendation, Kraushaar laid out a gamut of factual nuggets from the study at the work session, most of which could cause Wilsonville residents to wince.
For one, the study indicates that 60 percent of drivers who enter the freeway at the Wilsonville Road on-ramp get off at either the Charbonneau or Canby-Hubbard exits and that the nearest alternative includes a 13-mile detour.
Also, to arrive at their destination 19 weekdays out of 20, a driver commuting within the bottleneck area during nighttime peak traffic must plan for the drive to take three times longer than it would when unimpeded by traffic. However, Kraushaar notes that trip times fluctuate wildly.
"The region is really going toward investing in improvements that provide more reliability. Even if you have to sit in traffic that's better than not knowing what will happen that day," Kraushaar said.
Kraushaar also indicated that the Wilsonville Road on-ramp could cause issues moving forward. The ramp includes a meter that limits the number of cars that can enter the ramp to 1,200 per hour, but the study indicated that the number would be insufficient by 2040. However, OTC could decide to increase the capacity of the ramp.
"Forty percent more drivers will want to get on I-5 at the Wilsonville Road on-ramp than will be able to get through the ramp meter. This is a pretty scary scenario," Kraushaar said.
The study found that the slowest nighttime speeds clocked in around 40-45 miles per hour in 2015 but have plummeted to 30 miles per hour in 2017. Also, vehicle speeds sometimes drop before 3 p.m. and remain reduced until after 7 p.m.
In addition, freight volumes along I-5 are 14 percent higher than other freeways in the region, 26 southbound busses occupy I-5 each weekday and delays lead to $750,000 in economic costs per mile annually in the bottleneck.
"This is something we need to pay attention to because freight plays a huge role in our economic success," Kraushaar said. "We're trying to note that there are a lot of stakeholders here that would benefit from any operational improvements to I-5."
Kraushaar said that according to Metro's model, I-5's traffic volume will increase by 15 percent by 2040 — though she added that this might be an underestimate. She also said the crash rate in the bottleneck is higher than average but that most crashes are minor.
Councilor Scott Starr suggested the idea of preventing weaving on the outermost left lanes of I-5 by changing the left lane to an express lane.
"Going back east and seeing how they do things in New Jersey and New York, they use that express lane a lot. If you aren't going to exit you just go and it seems like it has worked pretty well," he said.
The City of Wilsonville will present the City and ODOT's options in an open house 5 p.m. Wednesday, March 14, at Wilsonville City Hall. The public outreach period of the process runs through May and Wilsonville City Council will likely consider resolutions thereafter.