Corrupting a governor

| May 29, 2007

Today’s speed governors are far from being tamperproof. Making that a reality, though, would involve substantial costs.

Of the thousands of comments filed on the two petitions to govern truck speeds at 68 mph, one of the least debated topics is whether governors can be truly tamperproof. What appears to be a simple, password-protected system is, upon closer examination, not so simple or well-protected.

This already is a concern for many fleets, according to preliminary results from a study done this spring by the American Transportation Research Institute. In the study, 30 percent of fleet executives said they consider driver tampering with speed settings to be an issue. Moreover, 78 percent would fire or otherwise punish a driver for tinkering with the governor.
It’s a hot issue for manufacturers, too. “Our principal concern with the proposal is the suggestion that speed limiters be ‘tamperproof,’” wrote Robert Clarke, president of the Truck Manufacturers Association.

For example: To properly calibrate the governor with the speedometer, the electronic control module may require reprogramming after a change in tire size or rear axle ratio.

Another TMA concern is the cost of retrofitting all vehicles back to the 1990 model year, a tall order requested in the petition by Road Safe America and 10 fleets. (The American Trucking Associations’ petition calls for the mandate only on new trucks.)

Vehicles built in the early- to mid-1990s may require mechanical governors that TMA says would cost $1,000 to $1,500 per truck, depending on brand. “These devices are not tamperproof and can easily be reset,” Clarke wrote.

What TMA calls the simplest approach – securing the password more effectively – still would allow mechanics to make changes. Fleet managers could decide they wanted drivers to run faster than 68 mph, and order it done across the board, or a driver with the right influence in the shop could get his way.

A more secure approach would be to “modify ECM software to provide a fixed road speed limit that is not readily accessible to vehicle owners — i.e., make this a factory password-protected feature,” TMA says. In that case, anyone who wanted the governor adjusted would have to go through the manufacturer.

The most ironclad approach, TMA says, would be “Creating new engine control system hardware and software to ‘hard-wire’ existing vehicles.” Under such a system that’s separate from the ECM, it’s not clear how – or if – it could be adjusted to accommodate a change in wheel size or axle ratio.

Based on those levels of changes, TMA estimates the per-vehicle cost of retrofitting the 1 million trucks built since 1990 at as little as $100 or as much as $2,000. This means a price tag for U.S. fleets of anywhere from $100 million to $2 billion, plus the expense of software and hardware development borne by the vehicle manufacturers.

Even if regulators reject the retrofit proposal and focus on new trucks, the “tamperproof” challenge remains.

One way to access the ECM is with a plug-in tool specially programmed to communicate with the device. An alternative is with a computer equipped with special software. In some cases, the ECM can be instructed to disable the password requirement, ideal for a one-truck owner-operator who’s not concerned about ECM access or who would rather not bother with a password.

Comments are closed. strives to maintain an open forum for reader opinions. Click here to read our comment policy.