And then there were two.

For the past decade, the stoplights between interstates 694 and 35E along Hwy. 36 have been steadily disappearing, replaced with interchanges or overpasses to keep traffic moving along one of Washington County's major commuting corridors. It's part of the Minnesota Department of Transportation's ongoing effort to essentially turn that stretch into a freeway to downtown Minneapolis and St. Paul.

In 2005, the McKnight Road interchange was completed. That was followed by the Margaret Street overpass in the same year, the Rice Street interchange upgrade in 2011 and the English Street interchange last year. By the end of summer, the $13.8 million Hilton Trail interchange, replacing another set of stoplights near Pine Springs, will be completed just east of I-694.

That leaves stoplights in the Hwy. 36 corridor at Hadley Avenue in Oakdale and at Century Avenue (Hwy. 120), the border between Oakdale and North St. Paul. And their days are likely numbered.

A major question is what the redesign will look like. Those plans will include the additional complication of figuring out how the Gateway State Trail, the busiest bicycle and pedestrian route in Minnesota that runs parallel to Hwy. 36, will fit in.

The Washington County Board on Tuesday got its first look with MnDOT officials at the results of a study narrowing the redesign to two alternatives estimated to cost between $28 million and $36.6 million.

The more expensive alternative would include building interchanges at both Hwy. 120 and Hadley Avenue; the other would have an interchange at the more heavily-traveled Hwy. 120 and an overpass at Hadley Avenue.

The local governments involved in planning and funding the projects — Washington and Ramsey counties, Oakdale and North St. Paul — all support the two-interchange proposal. In fact, cutting off direct access to Hwy. 36 from Hadley Avenue would run counter to Oakdale's Comprehensive Plan and Washington County's Transportation Plan.

"We think this is an important project, and it's important for the east metro," said Wayne Sandberg, Washington County engineer.

It's not just a matter of making sure traffic keeps moving. There also are safety concerns. The two intersections have an accident rate — measured both in the number of crashes and their severity — that is more than double the average for similar intersections in the Twin Cities. The Hwy. 120/36 intersection is ranked No. 4 among the 200 worst intersections in the state, and the Hadley Avenue crossing is No. 95, based on data from 2009-11.

The interchange proposals call for a "compressed diamond" at Hwy. 120, and a "folded diamond" — essentially a half-cloverleaf — at Hadley Avenue, designs aimed at minimizing the need to take land for the right of way. Even so, the entry/exit ramps at Hwy. 120 would require removing a Dairy Queen and other small businesses, including a Starbucks coffee shop.

The design at Hwy. 120 would preserve the $1.3 million Gateway Trail bridge that was completed three years ago. The interchange at Hadley Avenue includes plans for a tunnel on the trail, which has to be slightly realigned.

Though the timing of the project is not directly linked to the increased traffic flow expected with the opening of the new bridge over the St. Croix River at Oak Park Heights in late 2016, Sandberg said it is a response to urging from U.S. Rep. Betty McCollum, D-Minn., to develop a long-term vision for Hwy. 36. McCollum had opposed the bridge in Congress, in part, because of increased traffic volumes on the highway.

McCollum's support could help the county secure a federal Transportation Investment Generating Economic Recovery (TIGER) grant for the Hadley Avenue interchange, Sandberg added, which would pay 80 percent of the cost.

If the county is successful in securing that grant, planning and development would be put on the fast track, much like what happened with Forest Lake's recently-completed Broadway Avenue reconstruction project, Sandberg said.

Mills Fleet Farm, which owns a large retail store, gas station and carwash at the corner of Hadley and 36 and stands to benefit from the project, has offered to donate land valued at $2.4 million. That shows how important both projects will be to economic development in the area, said County Commissioner Ted Bearth, whose district includes Oakdale.

Neither a timeline nor a definite source of funding for building the interchanges has been set. The projects are not yet in the funding pipeline from either MnDOT or the Metropolitan Council, but Hwy. 36 improvements are a priority for both agencies, said Karen Scheffing, a planner who led the study for MnDOT.

The highway is a prime candidate to be added to the MnPass toll system from Interstate 694 west to downtown Minneapolis, and could be an eventual route for bus rapid transit. The Metropolitan Council will begin a comprehensive study early next year of Twin Cities roadways best suited for conversion to freeways, Scheffing said, "and Hwy. 36 will probably be high on the list."