Blackmarsh Road Roundabout
Location: St. John’s, NL, Canada
Client: City of St. John’s
Duration: 2015
Key Staff: Michael MacDonald, Kevin MacDonald
Project Description
In 2015, Harbourside Engineering Consultants did the detailed design on one of the first roundabouts in the city of St. John’s Newfoundland.
Past planning by the City of St. John’s, with respect to the construction of the Team Gushue Highway, identified much needed infrastructure investments at nearby intersections. These investments were aimed at helping with traffic congestion and providing a streamlined, efficient traffic network. The goal was to accommodate this new piece of modern highway infrastructure in the city.
As transportation engineers, Harbourside understood that these types of intersections (adjacent to the highway) needed to provide for safe, efficient movement of traffic. At the same time, they had to be designed in a user-friendly way for pedestrians, drivers, cyclists, trucks and other road users. Further, this type of “gateway” intersection had to promote economic development in this area of St. John’s. This could be accomplished by creating a sense of local identity that would bring more people to the area.
HTC investigated the options of either a roundabout design or a signalized intersection for the Blackmarsh, Empire, Redmond intersection. In both cases, the intersection was to provide a prominent gateway feature for this area of St. John’s. The city determined that the final design would be a roundabout. This was clearly the best option to provide all users (vehicles, trucks, pedestrians, cyclists) with a safe, high-capacity intersection.
Harbourside’s Role
Before beginning the detailed design of the Blackmarsh roundabout, Harbourside needed to collect several data points. These data points included traffic flow, cost considerations, and more.
Harbourside tested the traffic performance of the intersection for current and projected traffic flows and future proofing consideration.
The selection of the final layout balanced and optimized the following parameters: Operations, safety, access management, geometry, aesthetics, environment, costs and public feedback.
Harbourside considered not only capital costs considerations but also analyzed life cycle costing. This included the following: Construction costs, maintenance costs (such as electricity and snow clearing), collision costs and congestion costs (time loss, fuel consumption, emissions etc.)
Harbourside detailed the intersection layout and geometric design, street grading and stormwater design, and the intersection/corridor lighting. Visualizations of the final appearance of the completed intersection were rendered using computer-generated animations.
HTC created the layout and design of all signage and pavement markings.
Harbourside handled the production of tender documents (drawings and specifications). These required little to no changes from submission to final execution.
Unique Challenges
The geometry of this roundabout proved particularly complex. In addition, many residential properties were in proximity to the intersection. This meant that several driveways, and Municipal services were in the vicinity, requiring robust traffic control during construction.
Social Impact
The original intersection was an operationally complex situation that did not take full advantage of its function as a major gateway into the West End. Nor did it take advantage of its placement as a major access point from the Team Gushue Highway. This redevelopment project not only improved the safety of the intersection but also introduced an aesthetic that welcomes citizens and residents into the West End along Captain Whalen Drive.