NCC Weekend Bikedays reduced pollutants and noise, Carleton study says

Carleton University professor at Civil and Environmental Engineering Liam O'Brien oversaw the study that was published in the Canadian Journal of Civil Engineering.  Photo by Spencer Colby /POSTMEDIA

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A recent Carleton University study has found that closing Queen Elizabeth Driveway to vehicles reduces particulate air pollution by 60 per cent and noise by 50 per cent.

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The research was overseen by Liam O’Brien, a professor of civil and environmental engineering at Carleton, even though his usual area of expertise is buildings. It was published in the current issue of the Canadian Journal of Civil Engineering.

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An avid cyclist who lives downtown and chooses not to own a car, O’Brien was inspired by the National Capital Commission’s Weekend Bikedays program, which reserves a stretch of Queen Elizabeth Driveway (and other parkways) for “active transportation” use by pedestrians and cyclists instead of motorized vehicles.

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In the summer of 2026, that has meant both lanes of the QED are closed from Fifth Avenue to Somerset Street between 8 a.m. and 8 p.m. on weekends and holiday Mondays.

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O’Brien knew he preferred biking on a car-free roadway, but his scientific mind wanted “concrete and objective” evidence on why it was better. The NCC’s Bikedays initiative made for a “natural” experiment, he said in an interview.

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“That’s when you have two conditions that naturally occur without the intervention of the researcher, where you can really compare two different scenarios,” the 44-year-old professor said.

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“In this case we could compare what people experience with cars and without depending on whether cars are allowed to drive there on a given day.”

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O’Brien suggested the idea to student Kabir Patel, an engineering undergrad, who ran with it. Devices to measure noise and particulate matter were rounded up, as well as a Health Canada expert in the subject, Ryan Kulka. Two master’s program students from France who happened to be visiting also participated in the research.

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Data was gathered over six days of similar weather conditions in June and July 2025. The roadway was closed to motorized traffic on three of those days and open on the other three. Measurements were taken three times a day at 12 locations along the 2.2-kilometre stretch of the Driveway between Pretoria and Fifth.

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Overall, the study showed greater benefits to car-free streets than simply giving people extra space to exercise. It’s a much healthier environment, O’Brien noted, with less pollution in the air and fewer noise disruptions. When traffic excludes vehicles, it also brings down stress levels and makes conversation with companions easier, he added.

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The research team came up with a composite noise–air pollution index that indicated a 60-per-cent decrease in overall exposure.

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A file photo from Saturday, July 22, 2023, shows cyclists on a motorized-vehicle-free section of Queen Elizabeth Driveway in Ottawa. Photo by Ashley Fraser /POSTMEDIA

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At a time when Ontario’s Bill 60 has forced the removal of Toronto bike lanes and a rethink of Ottawa’s cycling plans, it’s helpful to have data supporting car-free streets, O’Brien added.

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“It’s actually a way better business experience and way better for tourists and locals alike if we give some space back from cars to people,” he said.