McNamara Drive Roundabout Design
Location: Paradise, NL, Canada
Client: Town of Paradise
Duration: 2018 to 2021
Key Staff: Michael MacDonald, Kevin MacDonald, Robin King
Project Description
In 2018, the town of Paradise, Newfoundland, made considerable investments into improving its road networks. This investment required expertise in transportation engineering. The goal was to improve traffic flow throughout the town. As part of this initiative, a roundabout was planned for the intersection of Topsail Road and McNamara drive.
Harbourside Transportation Consultants provided the design of the new roundabout on McNamara Drive, which would also grant access to the new Intermediate School in Paradise. The work entailed upgrades to the intersection, the access road, and the services to the new school. These services included water main installation, storm water collection and conveyance, and wastewater collection.
Harbourside’s Role
To determine the best possible design for the area, a multi-phase approach was taken. HTC began with a Life Cycle Cost Analysis, leading to the preliminary design phase, followed by the detailed design, and finally the preparation of the tender documents for construction.
Life Cycle Cost Analysis. A life cycle cost was completed for the intersection to evaluate different types of traffic control and lane configurations. Three different options were included in our proposal. These were:
Option 1: Status quo. A signalized intersection with the existing lane configuration and timings.
Option 2: A signalized intersection with the addition of a dual left turn lane on the McNamara Drive approach, signal upgrades and an updated timing plan.
Option 3: A multi-lane roundabout.
The life cycle costs were compared over a 20-year period using several benefit and cost parameters. These included planning and construction costs, post opening costs, auto passenger time, truck time, and safety. The roundabout was identified as the preferred option for the intersection.
Preliminary Design. The preliminary design reflected the “best value” approach to mitigate potential cost issues in the future. The horizontal geometry of the roundabout was developed and optimized with respect to capacity, safety, construction costs and property impacts. The vertical profile, sight distances, utility locations and property lines were all considerations that influenced Harbourside’s optimization strategy.
Detailed Design. The final design included the horizontal geometry of the roundabout and the approaches. This extended out to a point where roadway rework was necessary. Our design package was complete with signage and pavement marking drawings, sight distances and landscaping restrictions (sight triangles). Entry angles, and entry path curvature analysis for the roundabout were developed in AutoCAD with diagrams and included turning movement diagrams for the design vehicle. Vertical design (road profiles, cross-sections and pavement elevations) where developed in Civil 3D, along with lighting layout drawings, and the location of storm drainage inlets.
Tender Package. After the detailed design was finalized, a tender ready package was completed with specifications, contract drawings and tender quantities. Harbourside is known for its attention to detail, with little to know changes to our drawing packages. Construction was undertaken by Farrell’s Excavating.
Unique Challenges
Safety was paramount in the design of the McNamara Roundabout. With the expectation that there would be heavy foot-traffic from youth from the Intermediate school, sightlines had to be as wide as possible. Visibility on approach was key, without infringing on property lines. In addition, special attention had to be paid to the installation of water mains, and wastewater collection from the new construction.
Social Impact
The design and construction of the McNamara roundabout helped improve Paradise’ overall road networks and provides accessibility to the new Intermediate School. With the focus on easing traffic flow, and enhancing safety, it allows for transportation by foot or by car throughout the town.
