A major commuter highway that bisects Washington County is being transformed to eliminate stoplights and pesky traffic bottlenecks, but five controlled intersections will remain within 4 miles of a new St. Croix River bridge.

The four-lane Hwy. 36, which runs west from Oak Park Heights and Stillwater to Roseville in Ramsey County, is seeing substantial upgrades this summer at two outdated intersections. The Hilton Trail project at Pine Springs, leading to Mahtomedi, will eliminate one of nine stoplights on Hwy. 36. The massive reconstruction of the English Street interchange in Maplewood will remove another.

"It's a critically important traffic corridor," said County Engineer Wayne Sandberg. "It's going to carry a lot of traffic. It's a major commuter highway."

The Minnesota Department of Transportation (MnDOT) has come under criticism in recent years from some mayors and U.S. Rep. Betty McCollum for what they said was a lack of Hwy. 36 planning in advance of the new St. Croix River bridge, which is to open in late 2016. The new bridge at Oak Park Heights, replacing the 1931 Stillwater Lift Bridge, would funnel increasing numbers of vehicles onto Hwy. 36, according to MnDOT projections.

The Lift Bridge currently supports fewer than 20,000 crossings a day. Many motorists using the bridge are Wisconsin residents commuting to work in Minnesota.

"Stillwater is a free-standing growth center all on its own," said Tom O'Keefe, a MnDOT planning manager. One of the complications of planning for Hwy. 36 traffic volume, he said, is that many drivers crossing into Minnesota tend to disperse onto other roads and to major employers such as Andersen Windows in Bayport.

O'Keefe said MnDOT has a 20-year plan for Hwy. 36 but "that is constrained to expected revenues."

McCollum and the mayors have been critical that the sheer cost of the bridge project — estimated at $690 million and shared by Minnesota and Wisconsin — will leave traffic needs on Hwy. 36 and nearby Interstate 94 underfunded.

"Residents along Hwy. 36 have long awaited projects to address current congestion along the corridor," McCollum said. "I am hopeful the upgrades underway this summer will bring improvements to safety and community access as well as relief to some frustration caused by daily traffic bottlenecks. Concerns remain about the long-term plan for other sections of the corridor that are at or above capacity — even as residents brace for the impact of projected growth in Wisconsin traffic, following the completion of the new St. Croix crossing."

The $17.3 million English Street project will eliminate a serious traffic bottleneck, but until late August motorists will have to take long detours around the site. At Hilton Trail, which leads north into Mahtomedi, the $13.8 million project has led to traffic diversions on temporary roads through the construction zone.

Both projects are scheduled for completion later this fall, with minor landscaping work planned next year.

That will leave seven stoplights on Hwy. 36, all of them in Washington County. Two of them in Oakdale — at Hadley, and at Century where Oakdale meets North St. Paul — are being reviewed in a new MnDOT traffic study.

The study commissioned for those intersections is significant because of concerns for safety along the popular Gateway Trail. A new pedestrian overpass opened over Century in 2010, but trail users still must cross through several lanes of oncoming vehicles at the Hadley intersection.

The Minnesota Department of Natural Resources has funding to build a bridge at Hadley, but that construction must be coordinated with a new traffic plan for that intersection, Sandberg said.

The stoplight-controlled Oakdale intersections, long on the radar for improvements, funneled about 28,000 vehicles daily last year. That number is expected to grow once the new St. Croix River bridge opens.

"Anywhere we have a stoplight we're going to have a backup," said Sandberg, who has been working with MnDOT and city leaders along the highway to unravel long-standing traffic snarls.

The Oakdale study to determine possible solutions will continue through the fall of 2015, but no funding is available yet for reconstruction.

Meanwhile, any possible elimination of five stoplights in the Stillwater area — all congregated in a stretch from Lake Elmo Av. in Lake Elmo to Osgood Av. in Oak Park Heights — depends on negotiations involving cities, Washington County and MnDOT.

"Different communities have different plans and visions," Sandberg said.

Two stoplights closest to the new bridge, at Osgood and at the Oakgreen/Greeley intersection, will remain. Those intersections, however, will be rebuilt to improve traffic flow with adjoining frontage roads as part of the bridge project.

Sandberg said Hwy. 36 is "critically important" to Washington County residents and improvements become more urgent because the county is projected to grow by 130,000 residents by 2030. Once the bridge opens, he said, "the big fear is that Wisconsin is going to grow" and Hwy. 36 will see far more traffic as a result.

For now, he said, "we're focusing on the intersections and bottlenecks."

Kevin Giles • 651-925-5037