More than 900 vehicles in Baltimore County, Md., now have GPS units installed, the Baltimore Sun reported. County officials believe the devices save about $100,000 annually on fuel costs by optimizing routes, but others question that figure.

"For a lot of the types of vehicles in a typical city or county fleet, GPS solutions have not been that cost-effective so far," Paul Lauria, president of fleet management consulting company Mercury Associates, told the Sun.

The county purchased their GPS system though NexTraq, paying $100,000 in startup costs and $288,000 in yearly fees. Advocates of in-vehicle GPS technology cite several other benefits that help offset system costs, including increased productivity and reduced vehicle wear and tear.

But some employee groups view the GPS devices as Big-Brother-style supervision, cautioning against using any information gathered by the system in employee disciplinary actions. Managers receive alerts if an employee drives faster than 12 miles per hour above the speed limit, if a vehicle idles excessively or crosses county lines.

The speed-tracking feature in particular has drawn many complaints from workers. "Most people won't admit it, but if you go 55 [mph] on the Beltway, you'll get run over, " said Norman Anderson, president of AFSCME Local 921, an organization that represents truck drivers and heavy-equipment operators.