OAKLAND, Calif. -- If there is a success story to be found in the auto industry's campaign to bring the most popular smartphone apps to the dashboard of the car, it is Pandora.
To date, more than 12 million drivers have activated the streaming music service. This summer, when J.D. Power and Associates released a survey showing many in-car technologies were going unused, Pandora was the exception: More than half of drivers surveyed reported using it within the first 90 days of buying a car.
Yet this popularity has come at a price.
Pandora, catering to automakers' varying specifications and visions, has spent large amounts of money and time to make its service compatible with dozens of brands and nearly 200 models. Some cars require a cable; others connect to Pandora wirelessly. Some rely on a smartphone; others don't.
"When you talk about the variety of ways to implement our technology, I think we've done every one possible," Pandora's chief technology officer, Chris Martin, said in an interview at the company's headquarters here. "Some of these are going to win, and some of these are going to lose."
Pandora can afford it, but smaller app developers cannot, so they're waiting for the auto industry to settle on a set of developer-friendly norms that can give cars the same versatility as smartphones.
Pandora sees cars as a big growth opportunity. The service claims just a 2 percent market share for listenership in the car, compared with 9.5 percent outside the car.
"There's a lot of upside there," Pandora Vice President Dominic Paschel told analysts in July, warning that it's "going to take some time for technology to work itself out, for people to figure out how to use it, for the best listener experiences to overcome the weaker ones."
The lack of a standard hurts that experience. Consumers can search Pandora's website to find out whether their car supports it. If the answer is yes, the website has no instructions; it urges them to "ask your local dealer or check your owner's manual."
Getting an app to work with diverse devices is a widespread problem for developers, said Owen Grover, general manager of Pandora rival iHeartRadio.
To get an app to work with a TV, for instance, developers can add the app to DVD players, gaming systems and set-top boxes such as Roku. Some devices will proliferate and some will disappear, but developers can't predict which are which.
"It's very easy to point to the automakers and say, 'Come on, everybody has got their own walled garden,'" Grover said. "But at the end of the day, Samsung has the same issues. Sony has the same issues. There are all kinds of nascent technology platforms."
As a result, larger app developers have no choice but to try everything.
"It's not up to iHeart to decide whether the OEMs will let Apple and Google wedge their way into the connected-vehicle experience," Grover said. "We're focused on the fact that there isn't one single pathway into the vehicle. We are not waiting for some fairy dust to get sprinkled on the process to make our lives easier."
If the process doesn't get easier, though, automakers may find themselves more vulnerable to systems such as Apple's CarPlay and Google's Android Auto, which offer the economies of scale that developers such as Pandora and iHeartRadio lack.
Consumers want something that "just works," Julius Marchwicki, a Shanghai-based director of connected-vehicle services at Ford Motor Co., said in an interview.
"Companies like Google and Apple are doing a really good job," Marchwicki said. "They bring a really good ecosystem to our vehicles, and they are, in many ways, the incumbents when it comes to working with developers."
This desire for a common approach is why Ford has encouraged other automakers to adopt SmartDeviceLink, Ford's interface for linking a smartphone to a car. In June, Toyota Motor Corp., which has not revealed any plans to offer CarPlay and Android Auto, announced it was looking at using SmartDeviceLink.
If a smartphone with Pandora is plugged into a car with SmartDeviceLink, the Pandora app will appear on a car's native infotainment screen, complete with Pandora's signature thumbs-up and thumbs-down buttons.
"Automotive companies compete very fiercely for sales and selling points, so going to other automakers and saying, 'We have this technology that we think you'd like,' is a difficult proposition," Marchwicki said. "It took us a significant amount of time, but we're starting to see some traction."