Oulu introduces rare traffic sign to reduce congestion

The northern Finnish city of Oulu will begin using a rarely seen traffic sign in May, replacing “lane ends” markings with “lane merge” signs to improve traffic flow at eight key intersections.

According to a report by Yle, the new signs require drivers to follow the “zipper principle,” where vehicles alternate from merging lanes without a clearly defined right-of-way. The change aims to reduce bottlenecks by encouraging equal use of both lanes before merges.

Saija Räinä, Oulu’s traffic director, explained that previous “lane ends” signs led to congestion as drivers avoided the terminating lane, overloading the continuing one. “Often, queues build up on the through lane while the ending lane remains underused—mostly just for overtaking,” she said.

The new signs will be installed at intersections where lanes previously ended, including major routes like Linnanmaantie, Tulliväylä, and Valtatie 22. Räinä acknowledged the transition may cause initial confusion but stressed the importance of adjusting speeds to the new system.

Unlike the old “lane ends” sign, which clearly assigned right-of-way to the continuing lane, the “lane merge” sign shifts responsibility to both drivers under the zipper principle. Temporary warning signs will alert drivers to the change during May’s installation period.

Finland introduced the “lane merge” sign in its 2020 traffic law update, but its use has been limited until now.