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| Fig. 1: A Uber prototype vehicle. (Source: Wikimedia Commons) |
Ride-sharing services have become increasingly popular in recent years, with companies such as Uber and Lyft providing several million rides each month. With a significant and growing ridership, these companies are posed to have significant impacts on traffic emissions in the United States. This paper discusses three factors contributing to these impacts.
Ride-sharing services can reduce emissions by reducing unproductive vehicle miles traveled and therefore making more efficient use of the vehicles on the road. Cramer and Krueger compared Uber's service to taxi services in five major cities. Their studies showed that Uber drivers had passengers in the vehicle around half the time that they were working. [1] Conversely, taxi drivers only had passengers around 30-50% of the time they were working. This more efficient use of vehicles on the road can reduce traffic and in turn emissions.
One significant aspect of ride-sharing on traffic emissions is its effect on public transit ridership. Ride-sharing services can act either as a substitute or a compliment to public transit, decreasing or increasing its use, respectively. Hall, et al. argued that ride-share companies act as a compliment to public transit, actually increasing public transit ridership. [2] The authors reasoned that ride-sharing is significantly more expensive than public transit, so that riders will still choose public transit over ride-sharing when possible. They claimed that ride-sharing fill gaps in the fixed-time and fixed-route transit services that would have deterred potential transit riders before. The authors found that ride-sharing firms increase public transit ridership by 5% after two years of operations. Increases in public transit usage positively impact emissions by increasing the number of occupants moved per mile traveled.
In the future ride-sharing firms are looking to use autonomy to improve their services. These firms are currently investing in research to bring about this new technology. One such firm, Uber, has created a fleet of vehicles to support this research, as shown in Fig. 1. Autonomous taxis could provide significant benefits in terms of reducing emissions and reducing fuel consumption. Greenblatt and Saxena claimed that the combination of efficient battery-electric vehicles coupled with autonomy in a taxi service may yield a significant improvement in emissions by 2030. By intelligently matching riders and reducing single-rider vehicles, green-house gas emissions of an autonomous taxi in 2030 are projected to decrease by 87% over its lifetime compared to an internal combustion vehicle in 2014. [3]
Ride-sharing firms have the potential to significantly reduce green-house gas emissions and reduce fuel consumption. By increasing car-pooling, increasing use of public transit, and intelligently increasing the number of riders per trip, they can improve the efficiency of vehicle travel. Combining these current strategies with future technologies promises a great potential for large reductions in emissions.
© John Talbot. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. Cramer and A. Krueger, "Disruptive Change in the Taxi Business: The Case of Uber," American Econ. Rev. 106, 177 (2016).
[2] J. D. Hall, C. Palsson, and J. Price, "Is Uber a Substitute or Complement for Public Transit?" J. Urban Econ. 108, 36 (2018).
[3] J. Greenblatt and S. Saxena, "Autonomous Taxis Could Greatly Reduce Greenhouse-Gas Emissions of US Light-Duty Vehicles," Nat. Clim. Change 5, 860 (2015).
