Abstract Manager

The Saskatchewan Ministry of Highways commissioned KGS Group to design a unique at-grade solution for a rural intersection on Highway 1 within Saskatchewan. The existing at-grade intersection is composed of a divided, high-volume primary highway and a low-volume local access road. Commercial development northeast of the project is driving an increase in the number of turning vehicles, specifically truck traffic. An interim at-grade solution was required to improve intersection safety while delaying the construction of a costly overpass until traffic volumes supported a grade-separated solution. Members of KGS Group were responsible for all three phases of this project, including functional planning through to detailed design and construction administration.

The Functional Planning phase began in 2020. Five different intersection alternatives were evaluated to improve traffic operations and safety. These alternatives included a directional island, increased median storage, median development, collector/distributor road, offset lefts, and a Restricted Crossing U-Turn (RCUT). The offset lefts, with a single lane roundabout north of Highway 1, was the selected design. This concept improved safety and operational efficiency by separating left-turn movements into two distinct T-intersections, allowing motorists to focus on one direction of travel at a time and is oriented to allow drivers to make their left-turn movements while travelling towards their desired destination as opposed to forcing drivers to backtrack.

The Design phase of this project was completed in 2023-2024. The 60m diameter roundabout was designed to accommodate a WB-36, as large truck traffic from Highway 1 and farm equipment would need to navigate the roundabout. Central and outside truck aprons were critical to allowing large truck movements while keeping the roundabout low speed for passenger vehicles. The offset left intersections, as well as the ramps leading to the roundabout, were designed to allow vehicles to accelerate as needed when diverging from or merging onto Highway 1. PG-64 asphalt binder was selected to increase rutting resistance due to decelerating and turning truck traffic.

The Construction of the offset lefts intersection took place in 2025, bringing its own challenges. Constrained to tie into Highway 1 while both roadways remained open, a temporary detour was constructed from a segment of the new onramp lane. Maintenance of the surface drainage through shallow grade change required precise culvert installation and ditch grading.

With this project now completed and the intersection fully operational, this design could be a case-study for future low cost, at-grade, twinned highway intersection treatments.