The Washington Post and DC.Streetsblog both report on a new study which estimates the potential savings in carbon emissions from car-sharing are relatively modest (see exhibit). The study was prepared by Rand Corporation for the US Department of Energy.
Car-sharing differs from car rental in a number of respects. With sharing, rentals are short term, fees are usually charged hourly, and cars are parked close to members’ dwellings or workplaces. It’s also much more reliant on automated systems for booking and accessing vehicles. And it’s up to members to keep cars clean.
Compared to owning, sharing reduces drivers’ emissions in three ways. First, drivers cover fewer kilometres, largely because standing costs like depreciation are incorporated in the hourly tariff. The perceived cost of driving is considerably higher and acts as a disincentive to low value trips.
Second, car-share vehicles are more fuel efficient. That’s partly because they tend to be newer, since they rack up kilometres fast and hence are turned over relatively quickly. It’s also partly because members can match the size of vehicle to the task. Owners on the other hand usually purchase a vehicle large enough for the most demanding task, notwithstanding that most of the time a smaller vehicle would be adequate.
The third reason is fewer vehicles need to be manufactured in the first place. One estimate cited by Rand is each car-share vehicle replaces between nine and thirteen privately owned vehicles.
Rand say car-share use is very low in the US at present – only 0.27% of drivers are members of a scheme. However they estimate there’s potential to expand to around 4.5% of the nation’s drivers. To put that in perspective, it’s roughly equivalent to half of all inner city drivers in a city like Melbourne using car share.
Surprisingly though, 4.5% penetration would only reduce total light vehicle emissions in the US by a measly 0.6%. Even if 12.5% of US drivers shifted to car share – a hugely ambitious target at present given the many obstacles to this form of tenure – Rand estimate the reduction would only be 1.7%.
That scant pay-off is primarily because the sort of people who currently use car share weren’t big drivers to begin with. They didn’t own many cars and they didn’t cover a lot of kilometres before becoming car-share members, so the reduction is from a small base.
There’re a couple of points to make about this. One is that some of the benefits – such as incorporating at least some standing costs into operating costs – can be achieved without resort to car-share. For example, vehicle registration could be loaded into the price of petrol or picked up using transponder technology. However the biggest component by far – depreciation – couldn’t.
Another point is car-share has other important benefits. For example, it reduces the amount of space devoted to on-street parking and the level of traffic in city streets. It also gives residents who want to drive a cheaper option than owning a car.
The most important point though is that Rand appear to have under-estimated the potential reduction in car use associated with sharing. Existing car-share customers were previously low car users, but if the market can be broadened to 4.5% of drivers and perhaps ultimately to 12.5%, then it will necessarily be attracting drivers at the margin who were previously much bigger car users. The reduction in emissions and fuel use would accordingly be larger.
I don’t think the low emission reduction is in any event a deal breaker. It’s neither necessary nor feasible to reduce the emissions associated with all activities by the same amount i.e. equiproportionately.
Better to prioritise effort on emissions-reducing activities where the ratio of pain to gain is more favourable and where the overall contribution is large e.g. shifting electricity generation from coal to renewable sources. Of course it’s pertinent that sharing doesn’t actually increase emissions.
Car-sharing still faces many problems, like insurance for younger drivers and access to parking spaces. The characteristic low density of most US suburbs makes it hard to provide viable parking within walking distance of dwellings and work places. Rand sound a cautionary note:
A 1994 study predicted that the market potential in Germany was 2.45 million members; however, ten years later, the market stood at 70,000….More than a decade ago, observers noted that actual membership rates were only 3 to 8 percent of projections of membership levels from a decade earlier….