Uber and Lyft have weathered criticism about pollution and traffic congestion for years, but it’s been difficult to get an exact gauge about how much ride-hailing contributes to daily emissions. A new study released today claims to have a more precise answer to this question.

According to the Union of Concerned Scientists, ride-hailing trips today result in an estimated 69 percent more climate pollution on average than the trips they displace. In cities, ride-hailing trips typically displace low-carbon trips, such as public transportation, biking, or walking. Uber and Lyft could reduce these emissions with a more concerted effort to electrify its fleet of vehicles or by incentivizing customers to take pooled rides, the group recommends.

“trips must be pooled and electric [and] displace single-occupancy car trips more often”

“However, those strategies alone will address neither the increases in vehicle miles traveled nor rising congestion concerns,” the report says. “For ride-hailing to contribute to better climate and congestion outcomes, trips must be pooled and electric, displace single-occupancy car trips more often, and encourage low-emissions modes such as mass transit, biking, and walking.”

It’s a tall order, but both Uber and Lyft have shown a willingness to reduce their carbon footprint. So far, their methods include introducing bike- and scooter-sharing services, integrated public transportation scheduling and ticketing into their respective apps, and incentive programs to get drivers to switch to electric cars.

Lyft rolled out a multimillion-dollar investment to become a completely carbon-neutral transportation service through the purchase of carbon offsets, while Uber explored providing cash incentives to some North America-based drivers who use electric vehicles.

But despite these efforts, the vast majority of trips that take place on both Uber and Lyft’s platforms are in gas-burning vehicles. The companies have tried promoting pooled rides, but customers have shown a reluctance to share their trips. Their efforts to better connect to mass transit have been slow and piecemeal at best. And their bike and scooter sharing services are subject to local regulations and market conditions, and as such can be unreliable.

A more systemic effort to address climate pollution has yet to emerge from either Uber or Lyft. And the solutions they’ve proposed so far are unlikely to address the core problem with ride-hailing: it is often more convenient and less expensive than other, less-polluting transportation options.

Update February 25, 11:39AM ET: “We want Uber to be a part of the solution to address climate change by working with cities to help create a low carbon transportation future,” a spokesperson said. “To unlock the opportunities we have to reduce emissions, we will continue to invest in products and advocate for policies that reduce car ownership, promote more pooled trips and support greater adoption of bikes, scooters, green vehicles and the use of public transit.”

Lyft, meanwhile, dismissed the report as “misleading.”

“This report, like many before it, makes misleading claims about rideshare,” a spokesperson said. “Lyft encourages the use of shared rides, was the first rideshare company to put public transit information into our app, and last year, made one of the largest single deployments of electric vehicles in the nation. We are eager to continue this work in partnership with cities, to advance shared, sustainable transportation.”