Telecommuting and stay-at-home restrictions for the COVID-19 pandemic created a noticeable impact on traffic, according to findings by the Maricopa Association of Governments (MAG). In March, MAG began tracking the amount of time commuters are stuck in traffic each day. Using speed data to determine congestion and travel time delay, the data cover all major freeways and most of the arterial streets in Maricopa County. “Traffic congestion is pretty much gone,” said MAG Executive Director Eric Anderson in mid-April. “As nonessential workers began telecommuting and people began staying home and off the roads, the overall traffic volume in the region was reduced by one-third during the first month of the pandemic. Daily congestion delay dropped by 50 percent,” he said. The data found that travelers experienced no significant congestion during any time of the day in April. Passenger car traffic saw the steepest decline. “This is likely the result of not only fewer people going to work, but a decrease in all trips, such as people taking their kids to school, going shopping, visiting friends, or driving to entertainment destinations,” said Anderson. Unlike passenger cars, MAG found that daily traffic for heavy trucks remained relatively consistent. This is likely because shipments of groceries, fuel, medical equipment, home deliveries and other such freight were not significantly interrupted. While it is still too soon to say with certainty, the reduction in traffic may have led to air quality benefits as well. MAG compared nitrogen dioxide emissions over the Valley during March 2019 and March 2020. Satellite data from six miles above the earth showed a 21.56 percent reduction in these emissions, which is clearly visible in the images. MAG Environmental Director Lindy Bauer said it is premature to say for certain how much of the impact is related to COVID-19, but in general, higher vehicle speeds and less congested roadways can help reduce emissions from vehicles. “There may be more emission reduction benefit from the fact that there are a lot fewer vehicles operating on the roadways right now than from the increase in vehicle speeds,” said Bauer. However, because nitrogen dioxide is a precursor to the formation of ozone, Bauer and other Valley air quality experts are hoping the reductions will result in lower summer ozone concentrations. “Since half of the nitrogen oxide emissions that contribute to ozone formation are from cars and trucks, we hope that a reduction in all types of trips will have a positive impact in the upcoming ozone season,” said Bauer. “Once more data is available to help understand what the effects of COVID-19 are, or have been, on air quality, there may be opportunities to study or understand how air quality during COVID-19 impacted public health.” Once the pandemic is over, MAG will continue to encourage people to telework and to avoid single occupant vehicle trips as effective air quality measures. “This unprecedented period may have demonstrated to employers and employees alike that teleworking is an effective alternative to work trips, or how some nonessential trips can be combined to reduce overall driving,” said Bauer. Due to heavy public interest in the findings, MAG created a web page with the information at azmag.gov/COVIDimpact . The information is updated weekly.