Congestion on Twin Cities freeways dropped slightly over the past year according to an analysis of metro area freeways released Tuesday by the Minnesota Department of Transportation.

MnDOT defines congestion as traffic flowing at speeds less than or equal to 45 miles per hour, and the percentage of time freeways were congested during morning and afternoon rush hours decreased from 23.7 percent in 2016 to 23.2 percent in 2017, according to the 2017 Metropolitan Freeway System Congestion Report .

The half-percent drop came as the seven-county area's population rose from 3.04 million people to 3.08 million, the report said.

"Population growth is one of several factors that affects congestion levels," said Brian Kary, director of traffic operations at MnDOT's Regional Transportation Management Center. Gas prices, transit ridership, road construction and the number of vehicle miles traveled, which generally goes up when the economy is doing well, also play a role, he added.

MnDOT collected data from more than 4,000 in-pavement or roadside radar sensors in October 2017 and compared the data to previous years. The agency used October because it is the month that represents regular traffic patterns.

The year saw the completion of projects such as Hwy. 610 through Brooklyn Park and Maple Grove, additional lanes opened on I-694 through Shoreview, the opening of the new St. Croix Crossing linking Hwy. 36 with western Wisconsin and completion of construction on I-94 between downtown Minneapolis and Brooklyn Center and downtown St. Paul and Maplewood.

"As a department, we target congestion hot spots through various construction projects—large and small—and employ strategies to help alleviate ongoing congestion on our metro freeway system," Kary said.

Freeways were more likely to be congested during the morning rush hour, defined as 5 to 10 a.m. During those five hours, 127 miles of freeway flowed at 45 miles per hour or slower for at least one hour. Several routes saw congestion of 2 hours or more, including westbound I-94 from I-35E to Hwy. 280, eastbound I-94 through the Lowry Hill Tunnel, northbound I-35W from the Minnesota River to I-494 and westbound I-494 between Cedar Avenue and I-35W in Bloomington.

Major highways commonly plugged up included southbound Hwy. 169 from Brooklyn Park to the Crosstown and northbound Cedar Avenue from Eagan to Minnesota River.

In the afternoon from 2 to 7 p.m., congestion was most severe on both directions of I-94 between the Lowry Hill Tunnel and Hwy. 280, which was jammed for more than 3 hours. Other pinch points with more than 2 hours of congestion included eastbound I-94 from Hwy. 280 to I-35E in St. Paul, northbound Hwy. 169 from Hwy. 55 to I-94 in New Hope and Brooklyn Park, and westbound I-694 in Shoreview. More than 171 miles of highways and freeways were congested for at least 1 hour a day.