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Study shows California traffic improving as rush hour peak spreads out after Covid restrictions

Flexible working arrangements may have made commutes better since than pandemic, researchers say.

(CN) — As surreal as 2020 was, one of the most uncanny parts was the normally clogged freeways of California being almost barren.

As vaccines rolled out and people began heading back to their offices, the freeways seemed to return to their jammed equilibrium. But a study published in the journal PLOS ONE on Wednesday found that traffic is actually getting better as peak rush hour times are now spread out. 

Using data collected over six years from over 3,600 sensors embedded in California freeways and some rural highways by the California Department of Transportation, researchers at the University of North Carolina found that while the number of cars traveling on the road is still similar to pre-pandemic figures, people are not traveling at traditional rush hour times as much as they were prior to the pandemic. And, they posit, this means traffic and congestion problems haven’t been as bad as they once were. 

“The Covid-19 pandemic caused massive reductions in automotive travel and thus in traffic congestion, but now traffic volumes have returned to near-pre-pandemic levels. However, congestion is caused not by overall traffic volumes, but by volumes at the peak hours. Even if traffic volumes return to pre-pandemic levels, differences in the temporal distribution of travel demand may lead to changes in congestion levels. Traffic flow is highly nonlinear. A small reduction in peak demand on a congested roadway can cause outsized reductions in traffic congestion,” the authors say in the study. 

Whether this means there isn’t a traditional rush hour when people used to have to drive to work in the morning and back home in the late afternoon and early evening, or rush hours are just more spread out, depends on specific roadways, said Matthew Bhagat-Conway, assistant professor of city and regional planning at the University of North Carolina at Chapel Hill, and the lead author of the study. 

“What we found is that the demand is more spread,” he said. 

Bhagat-Conway and his co-author found that before the pandemic, from 2016 to 2019, rush hour traffic meant a large amount of cars on roads at the same time, which caused congestion and a decrease in the flow of traffic. Post lockdown, defined as Feb. 16 to Aug. 18, 2022, starting on the day that the state’s mask mandate was lifted, the “peaks” of traffic have spread out, reducing congestion and gridlock.      

Why is still up for debate, Bhagat-Conway said, but the data strongly suggests it could be because some people continued to work from home, and the flexibility of work schedules since the pandemic’s stay at home orders were lifted.  

City planners and traffic engineers design roadways, like freeways and highways especially, around peak hour travel, not overall travel, Bhagat-Conway said. Municipal governments across the country spend billions of dollars of taxpayers' money each year trying to maintain, construct, and add onto roadways to make a dent in traffic and road congestion. Expansion of existing roadways, the study points out, come with significant problems, including pollution, accidents, and using valuable land which often affects and displaces low income communities and communities of color close to freeways and highways.

The audience for this study, Bhagat-Conway said, are those city planners and traffic engineers.

He asks if traffic patterns are changing “whether we necessarily need to make the same investment in infrastructure that we might have otherwise?”

“Public agencies use traffic counts for a wide range of planning activities — anything from determining whether additional lanes or infrastructure such as traffic lights are needed, to whether there is space on a road to add safe bicycling facilities without causing gridlock for motorists, to what mitigations developers are required to provide for their projects,” the authors of the study state. “In the wake of the pandemic, these factors may be changing. Using pre-pandemic factors that are no longer correct could lead agencies to overbuild infrastructure, leading to increases in cost, greater climate impacts, and ultimately induce more driving due to more widely available infrastructure. Public agencies should carefully consider future expansion plans, and consider planning for lower peak demand than they might otherwise based on pre-pandemic data. Even if travel continues to increase post-pandemic, if that travel is distributed differently, additional roadway capacity may not be warranted.”

Bhagat-Conway said he hopes to lead another study in a few years to see if the results of this one holds up. He believes they will, because traffic data has stayed fairly consistent between 2021 and 2022, and survey data shows that people expect their employers to continue to allow them more flexible work arrangements into the future.  

Categories / Regional, Science

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