Abstract Manager

The intersection of Cedar Street and Dewdney Trunk Road in Mission presents a unique challenge for urban planners. The intersection's complex geometry features a skewed west leg with a steep 8% grade, while the north approach reaches a 10% grade. In addition, heavy truck traffic complicated the design, especially with a school on the northwest corner and plans for future active transportation connections to a nearby park. To further complicate matters, the intersection had to be raised by 350-400 mm to accommodate future sanitary main upgrades. These constraints required a delicate balance between vehicle flow, pedestrian safety, and future infrastructure needs.

To address these challenges, the City of Mission engaged Associated Engineering to explore two design alternatives for the Cedar Street corridor: roundabouts and signalized intersections. The goal was to determine which option best meets performance, safety, and cost requirements while accommodating utility upgrades and active transportation connections. Associated Engineering developed conceptual designs for both options at key intersections, including Cedar Street/Dewdney Trunk Road and Cedar Street/Rosetta Avenue.

A major challenge emerged when assessing the feasibility of a roundabout at the Dewdney Trunk Road intersection, due to the steep grades and limited land availability. These constraints raised concerns about meeting the necessary design requirements, especially for larger vehicles like buses and emergency vehicles. To provide an effective design, the team carried out traffic modelling and a safety review to compare the roundabout and signal options. The study also considered the need for future utility relocations and the potential impact on surrounding properties. After thorough analysis, it was determined that a signalized intersection at Cedar Street/Dewdney Trunk Road was the more cost-effective and feasible solution, given the property constraints and the complexity of the existing terrain.

One of the key takeaways from this project is the importance of considering local conditions (particularly topography and limited space) when deciding between roundabouts and signalized intersections and allocating space for lanes and multi-use pathways. The study highlights how traffic analysis, safety evaluations, active transportation connectivity, and property limitations can inform decision-making in constrained urban environments, enabling municipalities to implement practical and cost-effective solutions that prioritize both safety and efficiency. This presentation will provide valuable insights for transportation planners and engineers working in confined corridors, focusing on how to address complex challenges when limited space and steep topography complicate intersection design.