Traffic signal optimization helps alleviate congestion and improves pedestrian safety along Saskatoon’s 22nd Street

The City of Saskatoon has a growing population and a traffic network that is under constant pressure to keep up with increased demand. 22nd Street is a major arterial roadway that is key to mobility in the city. A long railroad track separates the east and west sides of downtown and trains pass through three times per day, causing traffic delays of a half hour or more. In addition, with nearby residential developments along 22nd Street, at some locations, pedestrians avoid using the signaled crossings to get to the other side of road.

For a busy corridor such as 22nd Street, this practice had led to tragic accidents and fatalities. The City faced the challenge of solving the difficult issues of increasing traffic volume along 22nd Street, improving traffic management, and providing a safer environment for pedestrians. The City retained Associated Engineering to identify potential solutions. 

Early in the project, the Associated team recognized the value of involving City staff in the design process to improve our understanding of the issues and collaborate in the development of solutions. The pedestrian crossing issue had cost many lives. The City’s mandate was to create a traffic system that provides a safer road user experience for pedestrians, cyclists, and other active transportation users, while offering better service to all vehicular road users. Associated Engineering worked with the City to develop a priority sequence that would be followed to come up with a strategy. The priorities would be i) Pedestrians, ii) Intersection Operations, and iii) Traffic Flow. 

The project team collected data, created analysis files, and prepared tables and charts to define problem areas, such as collision patterns or non-compliance of signs and markings. Traffic Systems Discipline Lead, David Booker, advises, “We visited key sites at various times during the day to evaluate existing operational conditions. We then prepared an initial observations table to define deficiencies along the road.”

“Our traffic engineers employed various tools to complete an analysis of traffic operations, assessments of safety hazards, intelligent transportation system practices, and advanced traffic controller programming. Receiving support from the City to accept non-traditional timing practices was also very valuable.”

Most traffic engineering professionals are familiar with traffic tools such as Synchro, Vistro, and Vissum. However, TranSync is the newest analysis tool for signal coordination. A network Measures of Effectiveness (MOE) was developed through the Centre for Advanced Transportation Education and Research at the University of Nevada. Associated is the first engineering or consulting company in Canada to use this advanced program and Saskatoon has become the first municipal user of the software in Canada.

Traffic analysis tools alone cannot resolve issues. Creativity is required to come up with the right solution.

“Controlling traffic is like controlling a river. Once the road network is full, traffic will go wherever it wants. The key to successful signal timing is the control of traffic.”

Eliminating, or at least minimizing randomness, reduces unsafe conditions along a traffic network. From arrival rates and coordination patterns, to providing sufficient green time for each movement, and in the case of 22nd Street specifically, pedestrian timing and response, control is achieved through time-of-day plans which adjust the on-street timing of signals as volumes and composition of traffic change.

But changing signal timing by time-of-day was only the starting point. Traffic control tools were used to develop a robust solution. David tells us, “We developed Multiple Double Cycle patterns across the network. Local Zero Override allow really short-cycle lengths, and we used Pedestrian Recall by time of day so that during peak times pedestrians would not have to push the button as an automatic call was placed for them.” Vehicle platoons were kept compact, so each group could receive coordinated green signals as they approached each intersection. 

The final result is an efficient traffic network that makes people a priority over vehicles and leads to a 20% reduction in both delay and vehicular stops across the network throughout the day.

Our key personnel on the project included Jon Medori, David Booker, Ellen McLaughlin, Sabrina Chan, Erica Mthembu, Judy Yu, and Laurel Richl.