At what point might the quest for clean air also become a privacy issue?

As I read Frank J. Bohanan Jr.'s riveting take on the dark side of on-board diagnostics for cars and light trucks in the current edition of "SEMA News," I understood his concern. Unless efforts are made to eliminate the potentially negative aspects of on-board diagnostics, the danger of invasion into the domains of personal and business privacy can only grow.

Bohanan is director of technical affairs for SEMA, the Specialty Equipment Manufacturers Assn., a group representing aftermarket manufacturers of performance, specialty, and accessory equipment. For years SEMA has been struggling with technical issues surrounding the current generation of on-board diagnostic systems, generally known as OBD-II, an electronic superstructure intended to eliminate tampering with emissions-control systems.

Regulatory agencies and environmental groups tend to support OBD-II, largely because they believe it helps reduce emissions levels by ensuring that vehicles with emissions-control problems are repaired quickly.

Vehicle makers have gone along with OBD-II because it makes malfunctions related to emissions systems easier to diagnose and repair.

Until now, SEMA has been primarily concerned about what it sees as the unfair economic advantage OEMs have over the aftermarket with respect to OBD-II technology. The aftermarket is currently unable to obtain crucial software-related information from OEMs that would allow them to develop emissions-control replacement parts that are fully compatible with new vehicles.

More recently, SEMA has become equally vocal about the ethical concerns surrounding the potential privacy abuses related to on-board diagnostics.

If the next generation of on-board diagnostics comes about, Bohanan writes, personal privacy could become a casualty. Here's his reasoning: OBD-III would take future OBD-II technology, which will already have been "enhanced" relative to current systems, and add off-board communications capability. This, in turn, would enable the information in both the OBD-II and other on-board systems to be accessed and acted upon remotely.

With the new system, Bohanan says, vehicles could be monitored on an individual basis. Tracking parameters could include emissions information and vehicle speed, as well as the ability to immobilize vehicles by remote command.

While regulators claim that this would be impractical or undesirable, and heavy-duty diesel-engine makers insist they have no plans to incorporate a new version of OBD-II or its successor into their products, there's always the possibility that it could happen some day.

In fact, studies funded by police agencies make a strong case for what is euphemistically termed a "cooperative technology" -- a means of minimizing the need for dangerous high-speed chases. Indeed, immobilization technology is already required by law in Europe.

Some fleets may take the stand that vehicle monitoring could be a positive thing in that it would raise the bar for the entire industry and force all truck operators to adhere to higher maintenance and operating standards. I don't agree with this rationale, however.

Every American faces severe enough threats to his or her personal and/or business privacy. Every time we make an ATM withdrawal or a credit card purchase that data is recorded. The revelations about ease of access to supposedly confidential medical records are worrisome, to say the least. Much of this data is being used in ways we can only begin to imagine.

If allowed to progress to the next level, says Bohanan, OBD-II could ultimately threaten personal privacy in a very direct way. It would provide a means for state and federal governments, or others, to intrude into our lives via mass suspicion-less searches of vehicles.

It's vital that truck operators keep an eye on this. The industry must do what it can to ensure that engine makers, the Environmental Protection Agency, and CARB keep working to make the air cleaner, but not at the cost of compromising our personal or business privacy.