Measuring Mobility for Travel Efficiency & Carbon Intensity: Case Study of Uber 

Abstract
The lack of a standard approach for evaluating real-world emissions from transportation makes it difficult to understand their climate impact. For example, fuel efficiency is often used as a climate impact metric for conventional cars. Public transit operators, on the other hand, often report on total fuel consumption or CO2 emissions. As the goal of passenger transportation is moving people, we propose two standard metrics that can be applied across all modes to understand climate-related performance:

Travel Efficiency (TE) - passenger distance traveled per vehicle mile traveled
Carbon Intensity (CI) - emissions per passenger-distance

TE & CI aim to capture all of the CO2 emissions resulting from energy consumed from activities to move people and vehicles which include:

(1) Activities to refuel, maintain, service, park or relocate vehicles in preparation for passenger service
(2) Activities to move vehicles to pick up passengers
(3) Activities to move passengers

TE & CI application:
Private vehicle: When applied to private vehicles, drivers are generally considered as a passenger. In the case of someone driving alone (accounting for >60% of all vehicle-miles travelled in the US1), the vast majority of emissions come from (3) moving passengers. In some instances where the driver makes substantial deviations from optimal route, such as cruising to find parking2, emissions from (1) may warrant attention.
Public transit: For a typical transit system, all three activities can apply: (1) drivers/operators move vehicles around the yard or to service centers, (2) vehicles move between the yard and their first/last passenger pick-up location, and (3) vehicles offer passenger trips between stops. In all cases, the driver would likely not count as a passenger.
Ride-sourcing: For ride-sourcing and other on-demand transportation services, emissions can similarly result from all three activities. A driver may (1) reposition to an area of higher trip demand, then (2) accept a trip and travel to the passenger pick up point, and finally (3) pick up the passenger and continue to the destination. In some cases, drivers may also become passengers, such as when using destination-based features to end rider trips near desired locations.


Uber: We plan to share the first TE & CI results as applied to Uber’s platform at the conference. This is a part of Uber’s commitment to sustainable mobility, along with other commitments such as powering all of our US offices with 100% renewable electricity by 2025, and building partnerships with EV charging network companies including EVgo and Powerdot3. We believe reporting the current status of our service is the first step towards sustainable mobility.
TE is defined as the amount of passenger miles generated per vehicle mile. CI is defined as the amount of climate-related emissions required to move a person one mile. Having standard metrics is necessary to measure the current climate impact of transportation systems and to provide guidance on future efforts and policies to improve sustainability. We believe in the potential of on-demand point-to-point mobility to move the needle towards sustainability, with collaboration and partnership with other stakeholders and policymakers.