Combating Carbon Emissions on the Road through Car Sharing

By KJ Keijan Zhao

At the 2015 Paris climate conference, 195 countries set out to limit global warming to two degrees Celsius above pre-industrial levels. To achieve that goal, national leaders targeted the production and consumption activities that contribute most to surging carbon emissions. Among others, transportation constitutes 23 percent of global emissions caused by human. Road transport dominates global transport emissions (73.9 percent) with light-duty vehicles (e.g. passenger cars and light trucks) the biggest contributor within that category, making up more than half. Moreover, ownership rates of these light-duty vehicles show an upward trend, due to a positive relationship with GDP per capita [as shown in Figure 1 below]. As light-duty vehicle ownership becomes more prevalent, the associated carbon emissions make sustainable and innovative transport solutions not only important, but also urgent.

Figure 1. Worldwide Vehicle Ownership and GDP per capita
Source: The World Bank and International Road Federation

Car-Sharing as a Solution

In Europe, North America, and Asia, car-sharing has become an innovative and increasingly popular option. Car-sharing is a service that allows members to gain short-term access to vehicles. Unlike owning a vehicle, car-sharing implies variable costs on top of gas, such as an hourly or per-mile rate for use.  

There are two main ways that car-sharing mitigates carbon emissions: it can substantially reduce private vehicle ownership and facilitate a low-mileage lifestyle. For example, in the Netherlands, car-sharing lowered carbon dioxide emissions by around 175 to 265 kilograms per user per year about 8 percent to 13 percent of the vehicle emissions. In North America, studies show an even greater reduction of carbon emissions [Figure 2].

Figure 2. Annual Change in GHG Emissions in North America
Source: Mineta Transportation Institute

There is a counter argument, though: increased access to vehicles could incentivize more people to drive, and in turn, increase carbon emissions among those who do not own vehicles. Still, the substantial reduction of carbon emissions outweighs any small increase resulting from enhanced vehicle access.

In addition to reducing carbon emissions, car-sharing could address some common challenges in creating sustainable transportation systems. Financially, while environmental externality issues generally require government intervention, car-sharing uses private and social sector resources and may ameliorate the burden of government expenditure on mitigating carbon emissions from transportation. Moreover, as sustainable transport solutions often rely on technological change which requires substantial upfront investment, car-sharing may alleviate some financial stress in developing the transport system. Behaviorally, the user fees for car-sharing may incentivize drivers (especially owners of vehicles) to re-evaluate the necessity of driving and change their habits of driving in a non-radical manner. Such a moderate change may meet less resistance from drivers, given that green consumers are not the majority yet. The financial and behavioral factors further demonstrate the advantages of car-sharing in supporting the transition of the transport system.

However, the effectiveness of car-sharing in reducing carbon emissions in a specific locale depends on a few conditions. First, the quality and type of cars adopted in car-sharing schemes determine the amount of emissions mitigated. Since car-sharing organizations tend to offer a variety of cars, the proportion of vehicles with low emissions to those with high emissions affects the actual environmental benefits accrued. Second, the demographic characteristics of the region may influence the magnitude of impact of car-sharing schemes, as car-sharers tend to be younger (25-40 years old) and more educated  (bachelor’s degree or more) than the general population. Finally, car-sharing is a single part of the larger transport network whose success depends on other complementary services provided. Studies have shown that the quality and quantity of public transport and exclusive parking lots for car-sharing users are positively correlated with the utilization of car-sharing services.


To limit a country’s contribution to global warming, transitioning to a more sustainable transport system is crucial. As car-sharing can lead to a significant reduction of carbon emissions with moderate behavioral change and high financial viability, it can play a key role in this transition process. Considering the organizational and regional factors that may impact the effectiveness of car-sharing, I recommend the following strategies:

  • To increase the proportion of high-efficiency vehicles in car-sharing schemes, for example, by cooperating with producers of electric vehicles
  • To understand and address barriers certain demographic groups (e.g. the age group above 40 and the education group below bachelor’s) face in participating in car-sharing
  • To establish and strengthen other transportation strategies that are complementary with car-sharing, such as public transport

KJ Kejian Zhao is a Master of Development Practice (MDP) candidate at UC Berkeley.