Weekday traffic on all four major interstates in the Portland area is down 46% from levels last year, according to a report compiled by the Oregon Department of Transportation.

Interstates 5, 405, 84 and 205 are all seeing significant traffic declines, and the freeways are only becoming less congested as the weeks stretch on and our collective memories of a previous life fade away like Mt. Hood in the rear view mirror while driving on U.S. 26 toward Central Oregon.

Traffic on weekends is down even more precipitously, the state report found.

And as Portland police and other law enforcement agencies say that dramatic speeding on surface roads is up considerably, the state data show drivers are taking advantage of the free-flowing traffic conditions to rip through town.

I-5, in particular, is seeing the most significant declines of metro-area freeways. The average weekend traffic was down 64% for the most recent full week of data available (March 30-April 5).

According to Oregon Department of Transportation’s first COVID-19 monitoring report, released Friday, the largest decreases occurred initially on highways and freeways to the coast and mountains. The report looked at the change in traffic patterns in the past month, starting with the week schools closed, then subsequent weeks under a stay-home order as well.

“The largest decreases occurred on Oregon 18, U.S. 26, U.S. 20, U.S. 30 and U.S. 101, which see high use for commute and recreation-based travel,” the state analyst wrote.

Willamette Valley residents, it seems, were by and large avoiding the beach and the mountains, as directed. The drop on Highway 26, for instance, coincided with the city of Seaside’s order closing all its beaches the Monday after spring break tourists flooded in from Portland and elsewhere.

“Week two after the stay-home order reveals further decreases in traffic volumes in I-5, I-205, I-405, and I-84. U.S. 97 and U.S. 197 saw small increases in traffic volume relative to the previous week, likely related to rising truck freight movement,” the report said.

State officials compiled the data from 38 traffic monitoring locations across 13 freeways and highways in Oregon.

Traffic counts on 13 freeways and corridors in recent weeks

With wide open interstates and highways come the speeders.

According to the state data, as every week stretches on and slowly erodes portions of our collective souls, people are driving faster.

For example, average speeds on I-5 northbound during what used to be the afternoon rush hour were up to 60 miles per hour in the most recent week of figures. Back during the week of March 1, the average rush hour speed there was 33 mph.

The state found traffic is “mostly at free flow” across the metro area.

Average freeway speed in the Portland area

Freight traffic is a different story.

The state found that two weigh stations, in particular, have seen large increases in recent weeks: those on I-5 at Woodburn and I-84 near Huntington on the Snake River, roughly 30 miles from Idaho border.

This chart shows increases in orange and decreases in blue.

One way to measure freight traffic is by analyzing weigh stations statewide.

Here’s the full report.

-- Andrew Theen; atheen@oregonian.com; 503-294-4026; @andrewtheen

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