Two police officers are being prosecuted and another is under investigation for driving offences in which data from vehicle "black boxes" are being used against them.

The cases come as courts here explore the use of speed data from airbag control systems on some cars and manufacturers prepare for the possible introduction of black box technology on all new models.

Yesterday the police revealed prosecutions against two of their number over crashes involving police vehicles from which airbag data were retrieved, and said a third was being investigated after another incident.

Crash investigation national adviser Inspector Mark Stables told the Weekend Herald that information from airbag control modules was being considered as part of the investigations.

"It's not the be-all and end-all but rather another tool in the crash investigator's tool box," he said of the data, which could be retrieved only by sending the modules to the United States for analysis.

He did not have details of the crashes, but said none involved police pursuits.

Another recent case involved Hawkes Bay man Allan John Hohaia, 50, who is to be sentenced next month after the data suggested his high-powered V8 Holden Commodore Clubsport was travelling at 98km/h half a second before impact with another car in which the driver suffered multiple injuries.

Vehicle black boxes are controversial in the US, where a bill before the House of Representatives includes a requirement for data to be stored at least 60 seconds before airbags are activated, and for 15 seconds afterwards.

Although most modern cars already have black boxes in some form, these are primarily to help manufacturers improve safety features, and lawyers for victims of crashes in the US involving unintended acceleration of Toyota vehicles have accused the manufacturer of blocking access to data.

Mr Stables said access to airbag control module information in New Zealand was, so far, limited to Holden VE series Commodores (which made up the backbone of the police patrol fleet), Hummer SUVs and some Chrysler vehicles.

Even so, that means owners of about 20,000 vehicles could find the information used against them if involved in high-speed crashes, and the Motor Industry Association expects the number to grow with technological developments.

"Once we get into that situation, privacy and so on comes to the fore, but we have these issues with technology all the time," said association chief executive Perry Kerr.

Mr Kerr said his organisation was unlikely to take a position on the issue "because it will be driven by overseas suppliers and legislation in other countries".

But Privacy Commissioner Marie Shroff said many drivers might not know their vehicles had technology which could be used to prosecute them, and it was important for them to be aware of that.

Automobile Association spokesman Mark Stockdale said his organisation accepted the use of such information for criminal investigations but would be concerned if it became a standard tool for traffic enforcement or for insurers refusing to pay out for minor transgressions.

Ministry of Transport communications adviser John Summers said it had yet to evaluate the technology so had no proposals for "mandating its use at this time".

But he said the Government's 10-year road safety strategy favoured working with the motor industry to promote vehicle safety technologies as they became available.

Hohaia's lawyer, Catherine Clarkson, said he had been unaware the data collection technology existed in his car, and she considered using information for purposes for which it was not intended a breach of the Privacy Act.

Although the police obtained the information under a warrant, she said the document did not specify the removal of a mechanical part from the car, and US court cases had established such data could not be retrieved without the owner's consent.