Two men walk past vintage Mercedes-Benz cars at the Techno-Classic classic car fair in Essen Thomson Reuters By Edward Taylor and Jan Schwartz

FRANKFURT (Reuters) - German carmakers are considering the use of aircraft-style "black box" data recorders in self-driving cars, a contentious idea in a country worried about surveillance, but potentially a crucial step in getting the new technology on the road.

Mercedes-Benz and BMW are among automakers to have developed autonomous or semi-autonomous cars, along with technology firm Google.

But while some features, such as assisted parking, are commercially available, legal questions are hampering the roll-out of other technologies, such as automatic overtaking on motorways, and fully self-driven cars remain prototypes.

Installing an aircraft-style data recorder could help to address some of these questions by giving manufacturers and insurers clarity over who is liable when an autonomous car gets into a crash.

The issue is being debated by Germany's "roundtable on autonomous driving", a group hosted by government officials.

The group aims to ensure Germany does not lose its edge in car manufacturing and includes automakers, lawyers, privacy advocates and insurance executives tasked with identifying shortcomings in Germany's regulation, technological know-how, and legal framework.

"Whether cars should have a black box is one of the items being discussed," a person familiar with the deliberations, who declined to be named, told Reuters.

With 90 percent of accidents caused by human error, engineers at automakers are convinced cars should be given more leeway to intervene and help drivers in a dangerous situation, much in the same way computers help pilots land planes.

But a crucial issue to resolve, and one being debated by a subgroup of the roundtable, centers on liability.

German law does not distinguish between a car in an accident which was driving semi-autonomously or completely without driver input, even though there is an enormous difference technologically, and from the level of driver involvement.

To determine whether a car, its driver, or a third-party was primarily responsible for an accident, insurers and carmakers want to collect car data, including its speed and inputs from sensors, cameras and the driver.

Insurers could also use the data to draw up policies.

"We could create insurance premiums more tailored to a certain risk profile," said Martin Stadler, an expert for automotive matters at German insurer Allianz.

Who gets to gather vehicle data and how, though, is highly controversial in a country haunted by a history of surveillance from the Gestapo secret police and East Germany's STASI.

More recently, revelations by former U.S. intelligence contractor Edward Snowden that Chancellor Angela Merkel's cell phone and mass internet traffic was being monitored, prompted calls for even tighter privacy safeguards.

KEEPING THE SOFTWARE FIRMS AT BAY

Information about the location and speed of a car could also be attractive to advertisers and communications companies who could use the data for their own commercial purposes.

German carmakers say they want to take a restrictive line on how data from autonomous and semi-autonomous cars is used, a move that could make it harder for software and telecom companies trying to make inroads into the auto industry.

"We accept that personal data belongs to the customer, and that we are not entitled to do with it whatever we want," Thomas Weber, head of development at Mercedes-Benz told a conference on innovation last month, a comment which observers took to be a thinly-veiled swipe at Google.

"The fact that we take these issues more seriously than some other companies is an opportunity for German industry," he said.

Germany's Auto Industry Association VDA is holding talks about whether it is possible to reach a common position on how to deal with vehicle data rights, Weber said.

The roundtable hopes its stance on data security and other matters will form a template for a "European position" which other manufacturers can adapt. To promote its views, it has already held presentations at the United Nations and European Union.

Its position on data appears to be gaining traction.

"Ultimately the person who generates the data, the driver, should have the final say over how it is used," Allianz's Stadler said.

Earlier this month, Peter Mertens, Senior Vice President, Research and Development at Volvo Cars, told a conference: "Our view of autonomous driving is not to gather personal data and use this for business. Our vision is to make driving safer."

(Editing by Mark Potter)