Car sharing hasn’t taken off here the way it has in cities such as Portland and Seattle, and one of the reasons is cost — the state can charge a $3-a-day surcharge every time the car changes hands. That fee was designed for conventional rental cars, not vehicles that typically rent by the minute or hour so the driver can run a few errands. When the surcharge equals nearly a third of the typical hourly rate, it’s no surprise that customers are discouraged from signing up.

Advocates have tried and failed the past two legislative sessions to lift or prorate the state surcharge, arguing that charging the flat fee multiple times a day is unfair and has stunted the industry’s growth in Hawaii.

Right as they are about that, though, car-sharing advocates also recognize that they aren’t getting anywhere. So now they’ve smartly switched gears, backing companion bills in the state House and Senate that would create and apply a new surcharge specifically for car-sharing organizations.

This is a fair compromise. Lawmakers must settle on an equitable amount for the fee — as of yet undefined — keeping in mind that we should encourage affordable alternative modes of transportation and boost the chances that this environmentally sound practice will spread beyond the few Hawaii college campuses, military bases and businesses where it thrives now.

The timing is right, too, as an affiliate of German carmaker Daimler announced that it wants to establish its popular Car2go service in Honolulu. There’s no timetable yet for when the fleet of 150 Smart cars would get rolling, but if Car2go does enter the market, it would be by far the largest such operation in the state. The cars would be tiny, though, no small consideration for a potential customer who needs a temporary ride precisely because whatever cargo they’re carrying is too large for the bus.

Other companies offer full-size vehicles by the hour, including Enterprise CarShare, which has operated car-sharing programs at Marine Corps Base Hawaii, Hawaii Pacific University and the University of Hawaii-Manoa. Enterprise charges members of the car-sharing group an application fee, an annual membership fee and about $10 an hour to rent a full-size sedan, which drivers pick up and drop off at a designated spot.

On the U.S. mainland and in Europe, car sharing appeals especially to urbanites for whom parking is scarce and expensive, and who can get around mainly by foot, bicycle or mass transit; they pay to use a car only when they truly need it. The same should be true on Oahu.

The market is small now, but there’s obviously room for growth as the redevelopment of Kakaako adds more high-rise housing to the urban core and the rail transit project proceeds. It’s easy to imagine a future rail commuter needing to run a few errands in town after work, before heading home to Leeward Oahu on the train. Even now, many loyal patrons of TheBus need a car from time to time, whether for work or recreation.

SB 2731 and HB 1894 emphasize the potential of this local market, but visitors likely would appreciate the service, too, if they could pick up and drop off an inexpensive, short-term rental car in Waikiki after touring the islands for a few hours.

Car-sharing groups shouldn’t be completely exempt from a state surcharge, but neither should they pay more than their fair share.

Recognizing this unique niche with an appropriate fee should be a priority for any lawmaker who claims to be committed to environmental sustainability and flexible, affordable transit options.