“You can’t get too much slower than that, I don’t think,” he said.
Also between 2015 and 2016, travel speeds during the peak morning commute on I-205 slowed from 48 mph to 25 mph.
From 2011 and 2016, the number of crossings on the I-205 and Interstate 5 bridges went up by more than of 24,000 per day, but fewer cars are actually getting across during the morning and evening peak hours because of the increased congestion.
“This is similar to pouring water through a funnel, if you pour too much water all at once it’s going to back up and overflow on you,” Robins said. “What we’re doing is we’re putting too many cars across the bridges at one time.”
The congestion also affects C-Tran’s travel time during its commuter service into Portland. In an interview with The Columbian, C-Tran spokeswoman Christine Selk said buses traveling from Fisher’s Landing Transit Center during the peak morning period are supposed to reach downtown Portland in 26 minutes, but the actual average travel time is just under 40 minutes.
“We are constantly talking about commuter service and the challenges that we are up against when it comes to travel times into and out of Portland,” she said.
The data also show people leave earlier and later to avoid the worst congestion, but that makes the peak traffic periods last longer than before.
Also, as traffic slows on the highways the traffic delays begin to slow traffic at some intersections of major arterials, such as Fourth Plain and Andresen Road, Fourth Plain and Highway 500 and Highway 500 and Falk Road.
The data are compiled as part of an annual congestion monitoring report called the Congestion Management Process. The document provides data to local agencies to they can in turn develop strategies to address the issues.
At the next RTC meeting, staff will present information on traffic in Northwest Oregon. RTC staff will also present more specific data about where the bottlenecks are occurring throughout the corridors.
