Updates are sorely needed because scales in place for more than 20 years are too short to measure rigs up to 53 feet long, according to the Mississippi Department of Transportation.

"The new platforms are longer — allowing the entire truck to be weighed," said Willie Huff, director of MDOT Law Enforcement. "The old ones do that but are shorter, causing some verbal instruction from the officer to the driver about moving the truck a little back or forward."

As with the old scales, the new sensors will be under the paved ramps running beside the scale office. The upgrades to install new sensors over about six more feet of ramp are set to begin this month, along with new sensors for the agency's pre-pass system, which works like a toll tag system to allow drivers with permits in good standing to keep on trucking past the scales with telemetry logging their data.

Companies recognized by the agency who use pre-pass still may be pulled over randomly as part of a pre-set percentage in the computer-run system to check for proper paperwork, fuel, registration and weight to ensure quality, Huff said.

Scales to be addressed in the overall $3.6 million project include those along Interstate 10 in Hancock and Jackson counties, Interstate 59 in Pearl River County, Interstate 55 in DeSoto County, U.S. 78 in DeSoto and Itawamba counties and U.S. 72 in Tishomingo County. All are expected to be complete by June 30.

Fewer trucks passed the scales in fiscal 2009 than in 2008 due to the economy.

MDOT Law Enforcement statewide staff of 206 monitors weight of commercial vehicles on all interstate highways in Mississippi and on highways without scales. It also has the authority to make arrests for more serious violations of the law, including offenses involving illegal narcotics on trucks deemed suspicious during checks, thanks to a move by the Legislature in 2004 to allow the agency to access information like a trucking company's status to operate in the state.