All the carsharing companies I've seen have pretty subdued logos on their vehicles, sometimes to the point that you could miss them altogether.
Why? One reason may be that in the focus groups that start ups inevitably think they HAVE to conduct, they've probably heard some people saying don't want any logos on the car, while others, who think it will be cool to be driving a shared car, will say they'd be comfortable with "tasteful" identification. And so they put a couple of decals on the vehicle and call it good.
But why not "brand" the vehicles as well? City Carshare started out with the off-green VW Beetles which seemed to me to be a very effective branding strategy. (To this day when I see a green Beetle I think of City Carshare, first, and then Zipcar, which had the same idea about branding.) But, I've long felt that using a graphic element from the company logo in large format on the vehicle could visually "unify" the fleet in the public's mind. And now I've seen a good example - the Dutch Greenwheels logo (above). The graphic element probably ought to something abstract, and ideally "active" or "fun", and not just some big block letters. The element needs to become part of the "style" of the car - like racing stripes. Another benefit of using these large graphic elements could help to visually unify a fleet that's become multi-colored over the years.
And speaking of graphics on cars, it wouldn't surprise if some day we'll see something even more extreme - a carshare that offers 2 classes of vehicles - the traditional car and the standard price and discounted vehicles that are "wrapped" with advertising, either for themselves or for other companies.
