A new study has found that ride-sharing servicesresult in much more pollution than other kinds of private and public transportation.Ride-sharing trips also draw passengers away from more environment friendly methods of travel,like public transportation, walking or biking, the study found.Several studies in recent years have suggested that ride-sharing services like Uber and Lyftcan worsen traffic problems in cities, which continue to have high rates of private vehicle ownership.The new study, carried out by the not-for-profit group Union of Concerned Scientists,represents an attempt to center on how ride-sharing services affect pollution.The research examined the effects of ride-sharing services on seven of America's largest cities.Overall, the researchers reported that ride-sharing trips now "result in an estimated69 percent more climate pollution on average than the trips they displace."The study notes that the same passengers could have chosen to travel by bus, train, bike, scooter or on foot.One of the big reasons they give for this result is that ride-sharing vehicles are often driven with no passengers in the car.This happens when drivers are either waiting for rider requests,are on the way to pick up passengers or are driving in between pickups.This situation, known as "deadheading," takes up about 42 percent of all ride-sharing driving activity, the study found.The researchers said that deadheading results in about 50 percent more carbon dioxide than one person driving in a private vehicle.Both Uber and Lyft do offer a choice of a "pooled" ride, which involves drivers picking up additional riders during the same trip.The study urges services like Uber and Lyft to work to increase the amount of pooled rides.It also urges the two companies to increase the number of electric vehicles on the roadand to improve connections to public transportation centers.Both Uber and Lyft have said in the past that most studies on the subject overstate the effects of their services on pollution.They have noted that the majority of vehicles on the road belong to private individuals or companies.Uber told Reuters news agency in a statement it had no comment on the latest report.But the company said it aims to be part of the solution to address climate change by working directly with cities.The statement added that Uber would continue to promote pooled trips and other means of transportation.Lyft told Reuters in a statement that the study made misleading claims about ride-sharing.But the company said it shares the goals of increasing the number of pooled rides and putting more electric vehicles in service.Both companies already operate businesses that offer electric scooters and bikesand have begun to include public transportation information in their systems.In some cities, they have also promoted vehicle electrification.