The humble smartphone could throw a spanner in the works of the car sector’s post-crisis turnaround, with the big manufacturers facing a long-term threat from apps that make it easier and cheaper to share or hire vehicles than to buy them.

Investor sentiment is on a knife edge. Car sales are back in recovery mode in most major European markets, yet the fragility of the turnaround could yet be exposed by another economic slowdown while investors have flagged the potential danger posed by web-based services further down the road.

The rise of the likes of car hire app Zipcar and car-pooling rival BlaBlaCar are expected to present new challenges to mass-market carmakers such as Ford, GM, Volvo, Renault and Volkswagen while presenting fresh opportunities for existing rental networks.

Online taxi business Uber is another seeking a slice of the market with its UberPop operation, which links private drivers to passengers, though the U.S. company faces legal challenges in countries including France and Germany.

Cathie Wood, chief executive of ARK Investment Management, is among the growing band of investment professionals expecting a significant behavioral shift among the car-buying public.

“Thanks to web-enabled services like Zipcar, Uber and Lyft, household vehicles are beginning to feel like the stranded assets they are: high in cost but utilized on average only 4 percent of the time in a 24-hour day,” she said.

The realization of such by consumers could eventually prove costly for carmakers. Specialist automotive consulting house AlixPartners says that every vehicle in a car-sharing network represents about 32 scrapped decisions to buy.

Heavy Backing

ARK Investment Management, meanwhile, says that a rise in car-sharing to 5 percent of all journeys could almost halve U.S. auto sales.

At this early stage, the projections remain a little nebulous and like-for-like comparisons between auto sales and car-share figures are particularly difficult. But it is clear that the trend is gathering momentum and there appears to be no shortage of backers keen to tap the austerity zeitgeist.

French billionaire Vincent Bollore unveiled plans to park 3,000 electric cars on London’s streets by 2016 as part of a car-sharing project announced in March. The Bollore group, which also operates car clubs in the French cities of Lyon and Bordeaux, said it would invest 100 million pounds ($157 million) on the U.K. initiative.

At a global level, the trend has the potential to slow automakers’ annual revenue growth to less than 2.5 percent from 3 percent between 2014 and 2020, according to Yasmina Barin, analyst at Swiss bank and fund management group SYZ.

The initial outlay for a vehicle and running costs that have soared for young drivers because of elevated insurance premiums are another factor in the growth of car-sharing or rental apps.

Uber’s latest funding round valued the company at $40 billion, broadly equivalent to the combined market capitalization of Peugeot, Fiat Chrysler and Volvo.

Gary Paulin, head of brokerage firm Aviate Global, said the trend would also benefit car hire companies such as Avis Budget Group and Hertz but could be more challenging for the traditional carmakers.

“The big listed automakers will need to adapt,” he said.

The market’s potential has certainly not been lost on Avis, which runs the Zipcar scheme that says it has more than 870,000 members in various locations around the world and in October launched operations in Madrid.

Hertz, meanwhile, has expanded its 24/7 car rental service to Europe and expects the number of vehicles included in the service to rise to about 500,000 by 2016, from 35,000 today.

On the Bandwagon

Among the manufacturers, some have been quicker to respond than others.

BMW became the latest entrant in London with this month’s launch of its DriveNow car-sharing service in partnership with rental firm Sixt. The scheme is already up and running in the United States, Austria and Germany.

Volkswagen’s Quicar is present in Hanover, while Daimler’s car2go operates in cities including Rome and Berlin, running 12,500 cars for a million customers.

SYZ analyst Barin believes that carmakers could still cope with the car-sharing phenomenon because the smaller cars used in such schemes might have to be replaced quickly and manufacturers could focus on producing such vehicles.

Yet for all their efforts to limit sales erosion, the manufacturers are likely to be left competing in a shrinking overall car market as a new breed of driver emerges.

“I thought about buying a car,” 28-year-old London-based PR executive Claire Rumbellow said, “but decided it would be cheaper and more practical to use a car-sharing scheme because I use a car only once a week at most.