Traffic crawls through the Highway 26-Interstate 90/39 interchange in Janesville on Wednesday afternoon. Freer-flowing traffic is expected when work on the interchange is completed at the end of the month.

JANESVILLE—Annoying traffic jams where Milton Avenue passes under Interstate 90/39 are temporary, a Department of Transportation spokesperson said Wednesday.

Only two of the three lanes of traffic are open in each direction at the underpass, and turning lanes also are closed, Steve Theisen of the DOT said.

The situation will get better when work is completed on the Kettering Street traffic signals at the end of next week and even better when lanes are opened and work is completed on the interchange, possibly by the end of the month, Theisen said.

Theisen said the work requires traffic to travel on pavement that doesn’t have traffic sensors, so the signal lights’ timing is not what it should be.

Some fine tuning of the traffic signal timing will be needed once the lanes are operating as designed, and after that, Theisen predicted “a vast improvement from what you see out there today.”

Weather could interfere with plans, but the intention is to have everything operational by Halloween, Theisen said.

The underpass is a diverging diamond, which is the first to be built in Wisconsin. It goes over the interstate at Avalon Road southeast of Janesville. The one at Highway 26 opened Aug. 31.

In a diverging diamond, traffic is diverted to the opposite side of the road, which allows exits and entries onto the Interstate without drivers having to worry about oncoming traffic. Traffic lights control the flow of traffic. The system is said to be much safer.

On Milton Avenue/Highway 26, the diverging diamond is between Morse and Kettering streets.

The Interstate 90/30 project is scheduled to be entirely complete by December. The project spans 45 miles from the Wisconsin/Illinois state line to Madison and it included the construction of 11 interchanges. The interstate was expanded from two lanes in each direction to three lanes in each direction, and to four lanes in the Janesville area.