Recent data from traffic analysis company Inrix reveals that Seattle-area Microsoft employees returning to the office three days a week are impacting commuters’ speeds on major roadways.

Inrix monitored travel speeds on key routes such as SR 520 and I-405 during specific weeks, indicating a noticeable decline in speeds due to the increased presence of Microsoft’s 50,000 employees commuting between Seattle and the Eastside.

The analysis showed a significant drop in travel speeds on SR 520, particularly on weekdays, with Tuesday, Wednesday, and Thursday experiencing the slowest speeds at just over 30 mph.

During the morning commute, speeds between Tukwila and Bellevue decreased by up to 35%, while the evening commute saw drops of 27% between Bellevue and Tukwila, and 21% northbound between Bellevue and Lynnwood.

Despite Microsoft’s new policy requiring employees to be in the office three days a week, the specific days are determined by individual teams and managers, with certain roles exempt from the mandate.

Relief for the region’s congested roadways is expected with the upcoming opening of Sound Transit’s Crosslake Connection on March 28, providing a light rail link between Seattle and the Eastside, including downtown Bellevue and the Redmond Technology station at Microsoft headquarters.

Previously: Microsoft’s new RTO policy started on Feb. 23, bringing back Seattle-area workers for three days a week.