Abstract Manager

The Province of Manitoba prioritized this infrastructure improvement project located west of Portage la Prairie, specifically focusing on the interchange at Provincial Trunk Highway (PTH) 1 and PTH 1A, as well as the nearby PTH 1 Overpass over the Canadian Pacific (CP) Railway. Constructed in 1968, the existing interchange structure had exceeded its design life and exhibited significant deterioration in all bridge elements. The interchange is a vital component of the Trans-Canada Highway network, facilitating traffic flow for increasing industrial development and the agricultural sector.

The project was driven by critical structural deficiencies and safety concerns, the bridge's substandard vertical clearance which led to a history of collision incidents and girder damage. Operational safety reviews identified further risks, including deficient acceleration lanes, tight ramp radii, and a history of collisions at the adjacent Road 40W intersection. Additionally, the project faced significant geotechnical challenges due to high plasticity clay soils, creating risks of settlement that complicated the design of embankments and profiles.

The primary objective was to replace the aging grade separation structure to improve traffic operations and structural integrity. Key goals included increasing the vertical clearance to at least 5.4 meters to prevent future collisions and bringing the interchange geometry up to modern standards to enhance safety. The project also aimed to accommodate the specific access needs of Long Combination Vehicles (LCVs) and large agricultural equipment, to extend the service life of the CP Railway Overpass by 15 to 20 years through rehabilitation.

The design transformed the existing trumpet interchange into a modified diamond interchange featuring roundabout ramp terminals. This methodology involved constructing a new two-span grade separation structure with precast prestressed concrete box girders and optimizing the vertical profile to minimize embankment fill and settlement risks. Two 60-meter diameter roundabouts were introduced to maintain traffic flow while managing traffic speeds. Truck aprons were installed both along the inside and outside of the roundabout lane to accommodate oversized  vehicles. Simultaneously, the CP Railway Overpass underwent intermediate rehabilitation, including deck replacement and the widening of the underlying service road to 10 meters.

The proposed design successfully addresses structural deterioration, safety deficiencies, and operational constraints while accommodating future traffic and agricultural needs. By closing the hazardous Road 40W intersection and re-routing access via the new roundabouts, the project ensures the continued reliability of this major transportation artery and safely integrates diverse user groups.