The Honolulu Police Department should stop using automated license plate readers, which gather vast amounts of data on innocent people, until it has sufficiently explained how this intrusive technology will improve public safety and has developed stringent policies to prevent abuse.

The HPD installed the high-speed cameras on three police vehicles about two weeks ago and is using them to identify stolen vehicles, a department spokesman told Honolulu Star-Advertiser reporter Rob Shikina.

The cameras are capable of photographing thousands of license plates per minute. The information collected is run through a database that can signal whether a car has been reported stolen or potentially been involved in another crime — a reasonable and legitimate use of the technology.

However, the readers can also be used to build a vast database of the driving habits of Hawaii drivers, which could be stored indefinitely and later used for any number of questionable purposes. Indeed, this has happened in other jurisdictions.

The department is working on a policy to govern use of the cameras, but it should have put rules in place before rolling them out, even on a limited basis. There are plenty of case studies to provide guidance, given that police departments in other U.S. cities have used similar technology for years — resulting in serious questions about mass surveillance. The Boston Police Department, for example, stopped using the scanners late last year after an investigation by The Boston Globe and the public-records group MuckRock revealed privacy breaches that underscored how easily the technology can be misused. Moreover, the investigation suggested that Boston police had not used the ALPR (Automatic License Plate Recognition) primarily to retrieve stolen cars — the reason they had cited for needing the scanners — but had gathered and kept vast amounts of data on motorists and their movements.

The American Civil Liberties Union also weighed in last year, with its comprehensive report, "You Are Being Tracked: How License Plate Readers Are Being Used to Record Americans’ Movements." That report, published in July, was based on information from 600 local and state police departments, as well as other state and federal agencies, in Washington, D.C., and 38 states — including Hawaii.

Honolulu Police Chief Louis Kealoha reported that HPD did not have ALPR from 2002 to 2008 (the controversial "Van Cams" designed to catch speeders were scrapped in 2002). HPD got a new ALPR system in 2008, but did not use it until February 2012; it was damaged beyond repair after three months.

In its report, the ACLU noted that license plate readers can serve a legitimate law enforcement purpose when they alert police to the location of a vehicle associated with a criminal investigation. But such "hits" account for a tiny sliver of the license plates scanned, the ACLU found, which means that too many police departments are storing records about innocent drivers. HPD should not be among them. Instead, the department should follow reasonable rules to ensure that officers use the technology without infringing on individual privacy and civil liberties.

Among the recommendations:

» Investigate only "hits" — license plates flagged by the database for violations — and in other limited circumstances in which law-enforcement agents reasonably believe data are relevant to an ongoing criminal investigation.

» Do not store data about innocent people for any lengthy period. Unless data has been flagged, retention periods should be measured in days or weeks.

» Allow people to find out if license-plate information about vehicles registered to them is contained in the database.

» Do not share license-plate reader data with third parties that do not follow proper retention and access principles. HPD must be transparent about what other agencies would have access to the database.

» Any entity that uses license plate readers should be required to publicly report its usage at least annually.

HPD owes the residents of Oahu much more information about this program. Automatic license plate readers have the potential to create permanent records of what and where virtually all of us drive. The overwhelming majority of motorists monitored by these cameras have done nothing wrong. Clear policies and regulations must be put into place now to ensure that law-abiding citizens do not relinquish fundamental rights in the pursuit of car thieves and other criminals.