For those who drive in and out of Portland every day, the findings of the Washington State Department of Transportation’s latest corridor capacity analysis might be the least shocking bit of news all week.
An improved economy and lower unemployment in the Vancouver area meant more people drove more miles and spent more time stuck in traffic along interstates 5 and 205 and state Highway 14 during 2016 than they did two years before.
The findings were published last month in WSDOT’s 2017 Corridor Capacity Report, the agency’s comprehensive yearly analysis of the performance of state highways.
“Traffic at specific locations on the corridors worsened from 2014 to 2016, with morning and evening weekday commutes experiencing moderate to heavy congestion on a daily basis,” the report reads. “Delay increased 83 percent throughout the corridors between 2014 and 2016.”
WSDOT studied the highways from the I-5/I-205 split down to the two bridges that cross the Columbia River. The analysis of Highway 14 was new to this year’s report; it includes the stretch of highway between Camas and the Highway 14/I-5 interchange.
“Combined routine congestion on the I-5, I-205, and (Highway)14 corridors in the Vancouver area increased from nearly three hours in 2014 to 11 hours in 2016,” the report reads.
The report also estimates that in 2016, morning commuters who traveled the 7.5-mile stretch from the I-5/I-205 split down to the Columbia River suffered the region’s highest costs due to congestion when measured by wasted time and burnt gas. Those drivers spent about $725 per passenger vehicle annually, the report finds. Return trip congestion costs weren’t measured because the traffic is experienced on the Oregon side of the river.
Average travel times for I-5 morning commutes through Vancouver increased by up to five minutes, while reliable travel times went up by as much as four minutes. For example, the average trip in 2014 from the I-5/I-205 split near Northeast 134th Street to the Columbia River took about 16 minutes, increasing to 21 minutes in 2016. On the same road, the reliable travel trip went up from 31 minutes in 2014 to 35 minutes in 2016.
When traffic gets worse and drivers slow down, fewer vehicles can make their way through the roadway network. To find out exactly how bad it was, WSDOT measured vehicle throughput on I-5 near Fourth Plain Boulevard, on I-205 near 10th Street and on Highway 14 near South Lieser Road. Throughput at those locations ranged from 100 percent down to as low as 56 percent.
The volume of cars moved through the system varied by travel direction, time of day and location. At Fourth Plain, nearly half of the corridor’s capacity was lost at 6:35 a.m. during the peak morning commute because congestion was so bad. Notably, traffic slowdowns in 2016 started earlier and were more intense than they were in 2014; but 2014’s congestion periods lasted longer.
Roadway congestion impacted not only commuters but also goods moving in and out of the state. Truck traffic accounted for a combined 18 percent of daily traffic volume on I-5, I-205 and Highway 14.
Compared with 2014, fewer commuters used public transit to travel the region’s major corridors.
On average weekdays, 1,650 people rode public transit along I-5 and I-205, a 19 percent drop from the estimated 2,025 who took public transit in 2014. WSDOT suggests that decline stemmed mostly from cheaper gas and a better economy.
