Traffic on Wisconsin highways has plummeted in recent weeks with schools and businesses closed as a result of the coronavirus pandemic, and that could have long-term implications, according to a study released this week.

The study from the nonprofit, nonpartisan Wisconsin Policy Forum examined 61 locations where the state Department of Transportation already collects data and found traffic had gone down by 40 percent from 2.5 million vehicles on March 3 to 1.5 million vehicles on April 7.

The declines aren't limited to the southeastern part of the state, which has been hit the hardest by the pandemic. When separated by region, all areas of the state have seen traffic decrease by at least 36 percent.

"From a public health perspective, this may be a positive indicator that residents in all parts of Wisconsin are staying home when possible to help prevent spread of the virus," the study says.

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The data include only highways, which means the extent to which traffic has declined on local streets isn't entirely clear, the study says. But highways that function as thoroughfares in Madison and Milwaukee have shown drops similar to the statewide average.

The decline in traffic seems to coincide with Gov. Tony Evers' decision to close schools on March 13, the study says. By the time Evers' stay-at-home order was introduced on March 24, traffic volumes had already fallen.

Since March 24, the amount of traffic on the highways has been relatively stable, which suggests residents "already had sharply curbed their use of highways, even before the state closed or curtailed the operations of many businesses and strongly encouraged residents to avoid nonessential travel," the study says.

Wisconsin State Patrol Sgt. Luke Newman has noticed fewer vehicles on the highways too, especially around times that would be busy under normal circumstances.

"The commuter traffic is less than it normally has been, which is nice that people can move a little more freely and a little easier to and from their work, if they have to go to work," he said.

With schools and many businesses closed, rush hour traffic has significantly dropped off. In Madison and Milwaukee, 44,000 vehicles were counted between 7 a.m. and 8 a.m. on March 30 — fewer than half the 98,000 vehicles during that same time period on March 2.

The data aren't yet available to determine whether the drop in traffic has actually led to fewer crashes, the study says.

"If fewer crashes are indeed taking place, it is likely fewer injuries and fatalities are occurring as a result, though that is not certain," the study says. The authors noted that if people are driving faster on clearer highways that could lead to more devastating crashes.

Newman has noticed a trend toward fewer crashes but said officers have stopped some vehicles driving at higher speeds lately because of a lack of traffic.

The sharp drop in driving could significantly reduce state gas tax collections, the study says, although the full impact won't be known until more data are collected.

"The loss of gas taxes will further exacerbate longstanding funding challenges for highways and other transportation infrastructure," the study says.

The Wisconsin Policy Forum also found that the steepest declines were among passenger vehicles, while transport trucks experienced a much smaller dip in highway use.

The study poses the question: How long will this trend last? Higher levels of traffic could return in a matter of weeks or months if restrictions begin to be lifted, the study says. But other factors, including high unemployment, continued health concerns and a long-term shift to working from home, could continue to have an impact.

"As with virtually all elements of the COVID-19 crisis, it is too early to determine the long-term impacts it will have on transportation policy and budgets," the study says.

Contact Chris Mueller at 920-996-7267 or cmueller@gannett.com. Follow him on Twitter at @AtChrisMueller.