“In order to explain our results, we pointed out the fact that the proportion of individuals who use Uber is quite small relative to the number of drivers in a given county,” Mr. Brazil said.

Teasing causation from correlation is tricky

Most studies, like Ms. Peck’s, have noted a correlation between Uber services and lower rates of alcohol-related accidents. A 2015 report from Temple University found that Uber was associated with a decrease in motor vehicle homicides in California. A report this year from researchers at West Carolina University also found that Uber service rollouts led to declines in fatal accident rates across the country.

But none of these reports has been as unequivocal as the one Uber itself released in 2015. It stated that in several major cities, Uber ridership peaked at times when drunken driving accidents tend to happen.

It also found that in Seattle, the introduction of services was associated with a 10 percent decrease in arrests for driving under the influence. And in places where Uber was launched in California, it reported, the number of alcohol-related crashes every month decreased by 6.5 percent among young drivers.

“Several independent studies have shown Uber’s presence in cities can help reduce drunk-driving,” a company spokeswoman said. “We’re glad to provide an alternative to drunk driving that helps people make safer, more responsible choices.”

Ms. Peck, whose research used collisions data from the New York Department of Motor Vehicles and the state’s Department of Transportation from 2007 to 2013, agreed that the growing body of research suggests ride-hailing services lead to less alcohol-related car accidents.