For more than a month, governors in a vast majority of states have urged people to stay indoors and away from one another, critical measures needed to slow the spread of the coronavirus.

But as the lockdowns drag on, the weather gets warmer and some states move to reopen, researchers at the University of Maryland have found that more people across the country are going outside, that they are doing so more frequently and that they are traveling longer distances.

The changes in behavior, tracked using cellphone location data, have been measured in the past two weeks and can be seen in all but three states.

Starting in mid-March, when most stay-at-home orders were announced, fewer people went out and people also made less frequent trips, according to the research. For weeks, the numbers held steady. Then, starting on April 14, the data showed people increasingly going out, a trend that continued through Friday, said Lei Zhang, director of the Maryland Transportation Institute at the University of Maryland, College Park, which is leading the research.