Construction of a freeway interchange unlike any other in metro Toledo is scheduled to start early next week.

Workers at the Central Avenue interchange on I-475/​U.S. 23 in Sylvania Township will start by repaving the freeway’s shoulders and repainting lane stripes so traffic can be shifted to the right, while new lanes are built in the median, said Phil Senn, the Ohio Department of Transportation’s project engineer. 

Archbold-based Miller Brothers Construction has a $38,921,841.26 state contract.

The initial work will require nighttime lane closings, Mr. Senn said.

But while widening the freeway from four lanes to six between Central and Bancroft Street is a part of the project, it’s not the centerpiece.

That will be the completely new interchange layout: a “single-point urban interchange,” a design tailored to high-volume arterial streets that features a central, six-way intersection that handles all left turns.

Central Avenue will be realigned where it crosses I-475/​U.S. 23, to minimize the amount of new right-of-way needed for the project and to reduce lane and ramp closings by building the roadway in the existing interchange’s grassy infield areas.

The project “addresses capacity and safety in this area, and sets us up for future widening of the corridor,” Todd Audet, ODOT’s district deputy director in Bowling Green, said two years ago during a meeting.

A public meeting, to explain the project to nearby business owners and residents, will be Thursday at 1 p.m. at Southview High School, 7225 Sylvania Ave.

The project also will include rebuilding Central between I-475 and the western end of a recent project to add turn lanes to Central’s intersection with Holland-Sylvania Road, Mr. Senn said.

Lane restrictions on Central will start next year. When that ends, Central will have a median divider from Holland-Sylvania to McCord Road, with gaps at selected intersections.

“There will be little to no impact to Central Avenue this year,” Mr. Senn said.

Next year also is when extended ramp closings are planned at the interchange for tie-ins, he said.

“There may be some minor closings this year to tie in temporary work,” he said. But next year the southbound interchange ramps will be closed for up to nine days and the northbound ramps for up to five, plus later three-week closings of the northbound exit and southbound entrance.

No ramp closings will occur during holiday weekends or the annual ladies’ professional golf tournament in Sylvania, Mr. Senn said. The contract requires penalties if ramp closings run long.

Also included in the contract is a late-2016 “interim completion” deadline by which the interchange’s final traffic layout must be in place, he said.

Single-point urban interchanges offer the functions of a traditional cloverleaf design while taking up less land and eliminating the weaving and merging a cloverleaf has.

While the Central Avenue single-point urban interchange is the first to be built in the Toledo area, several have been built in metro Detroit and the Columbus and Cincinnati areas. An example closer to Toledo is at I-94’s U.S. 24 interchange near Taylor, Mich.

The “single point” refers to a central intersection on the surface street that handles all left-turning movements.

A traffic-signal array has three basic green phases: for through traffic on the surface street, for traffic turning left from the exit ramps, and for traffic turning left onto the entrance ramps.

Traffic turning right onto the freeway entrance ramps typically does not have a stoplight; instead, it normally yields to traffic entering those ramps via left turns.

Traffic turning right from freeway exits may have a signal or a yield sign. If it has a signal, such traffic typically gets a green light during the same phase as the green for traffic turning left from the surface street onto the freeway entrances, because those movements don’t conflict.

The single-point design improves traffic flow by eliminating conflict points, allowing simultaneous left turns, and reducing time between signal phases. 

It also can create a softer angle for left-turning vehicles, useful at sites with significant tractor-trailer volume.

While saving space and improving efficiency compared to cloverleafs, single-point urban interchanges are relatively expensive to build because the central intersection requires a larger bridge — either for the freeway passing overhead or, in this case, for building the intersection directly above the freeway.

The I-475/​U.S. 23 widening to Bancroft will extend work that’s under way at the junction of I-475 and U.S. 23 just north of Central.

That $14.3 million project, which features construction of a new ramp for through traffic on southbound U.S. 23 and separating traffic flows for the Central exit from southbound U.S. 23 and westbound I-475, is set for substantial completion this fall and is on schedule, said Theresa Pollick, a spokesman at ODOT’s Bowling Green district office.

Contact David Patch at: dpatch@theblade.com or 419-724-6094.

First Published July 27, 2015, 4:00 a.m.