Researchers from the non-profit organization Union of Concerned Scientists (USA) calculated the increase in CO2 emissions after the start of the massive use of taxi services. Over the past decade, travel using Uber, Lyft, Yandex.Taxi has gone into the billions, and they are carried out using private vehicles with internal combustion engines. Because of this, in large cities in the United States, emissions from passenger cars increased by 69%.
The studies were conducted in Boston, New York, San Francisco, Washington DC and the District of Columbia, based on data from open sources, statistics of the services themselves, information from drivers and information from municipal structures. The idea that moving away from personal transportation in favor of short trips in cheap taxis will reduce traffic in general and emissions in particular has been completely discredited in the study. On the contrary, no matter what service we are talking about, food delivery or group trips, taxis are inefficient everywhere and generate more harmful emissions.
The main reason is the poor logistics of Uber and similar services, where profit is at the forefront. Instead of following optimal routes in a given mode, taxis rush from point to point for the best price. But they only get losses due to the so-called "dead miles" (the distance traveled between the points of disembarkation of the last passenger and the landing of the next). They don't pay anything for them, but the motors run and generate emissions.
It is unlikely that it will be possible to change the business model of services, but everything can be radically changed by replacing the main taxi fleet with electric transport. But how to stimulate thousands of drivers to switch to electric vehicles is still an open question.