Cornwall Interchange Design
Location: Cornwall, PEI, Canada
Client: PEITIE
Duration: March 2017 – September 2018
Key Staff: Michael MacDonald, Kevin MacDonald
Project Description
In 2016, the Prince Edward Island Government requested funding from Ottawa to redirect the Trans-Canada Highway around the town of Cornwall. The goal was to improve safety standards on this busy stretch of highway, and to mitigate the heavy traffic in-and-out of the region. According to the CBC, in the span of just 4 years (2009 to 2013), the area saw 159 collisions (none of them fatal). The project was to be completed in two phases. Enter Harbourside Transportation Consultants!
HTC provided consulting design services for the new Trans-Canada Highway bypass in Cornwall, PEI. Acting as the primary transportation engineers, the design consultation included two roundabouts, connector roads and interchange ramps. It also included the roadways approaching, and in between the roundabouts. Harbourside’s scope of work was for the preliminary and detailed design of all elements mentioned above. It also required specialized design for all the sectional elements. This included pavement, profile, cross fall transitions, and supporting infrastructure.
With such an important roadway, Harbourside’s attention to detail was critical. We had to see things from every angle.
Harbourside’s Role
Prepared Drawings in CIVIL 3D. This was to define the clearing limits and daylight lines. Our goal was to minimize property requirements.
Designed the interchanges and alignments. This was done in accordance with PEITIE standards, the Canadian Roundabout Design Guide, and the TAC Geometric Design Guide for Canadian Roads.
Developed and optimized the horizontal geometry of the roundabouts. This was done with respect to capacity, safety, construction costs and property impacts. Many considerations influenced this optimization. These include vertical profile, sight distances, utility locations and property.
Provided the horizontal geometry and curb layout for the roundabout. Using this data, predesign was done in AutoCAD.
Detailed design of the connector road and two roundabouts.
Specified sight distances and landscaping restrictions (sight triangles). Harbourside also specified entry angles, and fastest path analysis for the roundabout. This was done using AutoCAD with diagrams for submission to PEITIE.
Developed turning movement diagrams for the design vehicle, as specified by NLDTW.
Provided contract drawings and tender quantities for the roads and roundabouts.
Placement of storm drainage inlets.
Unique Project Challenges
The Cornwall interchange and roundabouts is located near several water sources. Specific attention was paid to nearby streams, water crossings, wetlands, and water transmission mains. It was imperative that, during development, these ecologically vital areas should not be negatively impacted. Minimizing run-off from construction and reducing travel near and around sensitive water sources were prioritized when designing for this project.
Social Impact
The development of the Cornwall interchange and roundabouts has allowed for heavier traffic to come in and out of the Cornwall area. Transportation and vehicular traffic, once ‘bumper-to-bumper’ along this section of the Trans-Canada Highway, now flows smoothly.
Alleviating the congestion has also helped improve tourism in the area.
Our Team
Harbourside’s key staff on this project were Michael MacDonald, and Kevin MacDonald. Michael was one of the lead writers of the Transportation Association of Canada Canadian Roundabout Design Guide.