Highway 1 – Lower Lynn Interchange Improvements address traffic congestion and safety issues
March 30, 2022
The Trans-Canada Highway / Highway 1 is the main route and a critical transportation link for people, services, and goods movement in British Columbia. In the Lower Mainland, the Highway 1 corridor connects Metro Vancouver to the North Shore, the Horseshoe Bay Ferry Terminal, and Highway 99 leading north to the communities of Squamish, Whistler, and Pemberton.
The interchanges immediately north of the Ironworkers Memorial bridge on the North Shore were designed and constructed more than 50 years ago. These interchanges are collectively referred to as the Lower Lynn Interchanges and include Mountain Highway, Keith Road/Mount Seymour Parkway, and the Main Street/Dollarton Highway Interchanges. With age and the growth of surrounding communities, the interchanges required improvements or replacement.
The BC Ministry of Transportation and Infrastructure divided the interchange improvements into four phases. Associated Engineering was responsible for detailed design and construction services for the Mountain Highway Interchange (Phase 1) and the Dollarton Highway/Main Street Interchange (Phase 3). We were also involved in the functional design of the Lower Lynn Connectivity Improvements Project (Phase 2 & 4).
Priscilla Tsang, Senior Transportation Engineer and Deputy Design Manager/Project Manager, tells us, “The projects included improvements to address traffic safety, queuing, and delays."
"The new interchanges will help improve traffic flow and travel times along Highway 1 and the Lower Lynn Interchanges, and upgrade transit and active transportation connectivity and safety.”
Mountain Highway Interchange: Associated provided detailed design and construction services for the new Mountain Highway interchange to improve multi-modal connectivity, capacity, and safety. The project includes a partial diamond interchange; a five-lane underpass; median and shoulder widening; realignment and widening of Mountain Highway; reconfiguration of the Brooksbank Avenue/Keith Road intersection; pedestrian and cycling facilities; and active transportation connectivity improvements, including a new pedestrian tunnel. Our team provided roadway, structural, drainage, and utility designs, as well as traffic engineering.
Dollarton Highway/Main Street Interchange: Associated completed preliminary, functional, and detailed design for upgrading the Dollarton Highway/Main Street Interchange to improve traffic flow and safety. Key components include a new eastbound on-ramp overpass at Main Street, two-retaining walls, on-ramp widening, a Highway 1 eastbound emergency pullout, and sidewalk/multi-use pathway improvements on Main Street. A unique feature of the design is a lane sharing and transit priority traffic signal to control the traffic from Phibbs Exchange and the Dollarton Highway and Main Street on-ramps to Ironworkers Memorial Bridge.
Situated adjacent to other project phases, constructability and schedule optimization were very important to optimize construction sequencing and reduce costs of all four phases. Efficiencies in budget and schedule were identified during value engineering and resulted in cost savings to the Mountain Highway interchange. The design also accommodated the future six-laning on Highway 1 and the replacement of the existing Lynn Creek Bridge in the future.
The geometric design was particularly challenging due to the highly constrained site, steep grades (about 8% on Highway 1 and 9% to 13% for Mountain Highway and the interchange on/off ramps), and close proximity to private properties. A tight diamond configuration minimized the footprint of the interchange.
The Mountain Highway Interchange required extensive retaining walls. Two major soil nail retaining walls were constructed, requiring close collaboration with the geotechnical engineers.
“The walls were finished with a shotcrete ‘rock-type’ facing, which makes them aesthetically pleasing and well integrated into the surroundings.” - Priscilla Tsang
Located within the project area, Keith Creek will be directly impacted by future climate change. Increases in peak rainfall intensities will result in larger peak flow rates, which will require larger infrastructure to safely convey these design flows through the project site. The design has a 20% allowance to account for increases in future rainfall intensities due to climate change.
The design included significant upgrades to pedestrian and cycling facilities along Mountain Highway, including a protected intersection at the Mountain Highway/Keith Road intersection, with separate pedestrian and cyclist crossings, as well as corner build outs to improve safety for cyclists.
Successfully delivering the project required extensive design coordination with the BC Ministry of Transportation and Infrastructure, City of North Vancouver, District of North Vancouver, Greater Vancouver Water District, Greater Vancouver Sewerage and Drainage District, FortisBC, Telus, Shaw, BC Hydro, environmental agencies, the local community, advocacy groups, Vancouver Coastal Health, HUB Cycling, North Shore Mountain Biking Association, Advisory Committee on disability issues, and design teams from the other project phases.
Our key personnel on the project included Ron Gratz, Priscilla Tsang, Shaun Bidulka, Ana Varhaug, David Harvey, Helen Du, Katrin Habel, Josh Thiessen, Jenna Lee, Helen Zhang, Sang Chung, Alfred Kao, Winnie Li, Jason Dowling, Helen Yin, and Siu Fung Ma.
