Abstract Manager

The Highway 401 Expansion project was a design-build project to widen a 18km long segment of the 401 from the Credit River in Mississauga to Regional Road 25 in Milton. The highway mainline was widened from 3 lanes to 5 lanes or from 3 lanes to 6 lanes in the express/collector sections.  The project, with a total budget of $640M, was designed and built under a very aggressive schedule.

Highway 401 in the Greater Toronto Area is the busiest and most congested highway in North America. The segment that was widened carries approximately 180,000 vehicles on average per day. Given the high traffic volumes and the highway’s importance for the economies of Canada and the United States, there was a requirement to maintain 3 lanes of traffic per direction and access to all interchange ramps during most of the day, 7 days per week. Lane and ramp closures were restricted to the overnight hours to limit impacts to motorists.

Maintaining the required lane and ramp access during construction proved to be one of the more challenging aspects of the project. Construction was staged to widen the highway on the outside (Stages 1A to 1E), then traffic was shifted to the newly constructed portion to allow for the reconstruction of the median portion (Stage 2A to 2C). Multiple temporary ramp alignments were necessary for each of the sub-stages at each of the 6 interchanges to accommodate the shifting work zones.

With the project awarded in April 2019 and the completion of the expansion in late 2022, a design-build model was used to allow work to commence with just a staging concept. Staging was developed in detail as the work progressed. This dynamic staging design was made possible through strong collaboration between the construction and the design teams. The traffic staging design team worked with the construction team to plan each sub-stage and developed the staging drawings to be submitted for approval.

This dynamic staging design saved a significant amount of time to complete the project on time. Though this often resulted in a high-pressure environment, with no float in the schedule, the team was able to meet the necessary timelines, and all lanes were opened for use by the end of 2022.