Changes to I-405 may be causing shifts, not just improvements, in congestion

Congestion on I-405 may not have improved since the express toll lanes and new ramps opened, so much as it’s shifted in some areas.

Though the Washington State Department of Transportation is seeing less congestion overall, it is reporting some congestion is actually just shifting.

For example, the new “braided” ramps that connect I-405 to SR 522 may have reduced a “major bottleneck in the northbound lanes during the evening commute.” However, WSDOT reports that some of the congestion moved farther north along the highway. That means that the travel times between Bellevue and Bothell have improved, but Bothell to Lynnwood, between Beardslee and SR 527, are experiencing more congestion in the evening.

Related: Drivers might not be warming up to I-405 tolls lanes

According to WSDOT, “It takes time for any big project to get up to full speed and we still expect it will take traffic six months to a year to reach full efficiency as drivers continue to adjust to the I-405 express toll lanes.”

The department has also seen a change in the time when congestion is the worst, which is why some people report that traffic seems to have worsened since the express lanes opened. There is more traffic earlier in the afternoons and more often on the weekends.

“While this is a win for drivers going the entire distance along the corridor, it certainly explains the frustrations some drivers who drive a shorter portion of I-405 are experiencing,” WSDOT says.

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Additionally, travel times on northbound I-405 during the weekdays have increased between 9-10 p.m. Compared to October 2014, there has been increased congestion at time on Tuesdays, Wednesdays and Thursdays.

The 17-mile trip from Lynnwood to Bellevue improved in general purpose lanes during the morning commute, WSDOT reports.

Despite the shifts in congestion, travel times during the third week of the express lanes have “improved slightly” overall.