For weight-sensitive fleets, the upside of maximizing payload is that it makes every trip worthwhile and increases profits. The downside is that cutting it too close raises the threat of stiff penalties for overweight law violations. In addition, there is the risk of serious liability claims for accidents involving overloaded vehicles.

According to one industry study, 58% of vehicles are still check-weighed at commercial platform scales. This results in lost time spent driving out-of-route miles to the scale, plus the cost of using the scale.

Given the very real possibility of discovering that the vehicle is overweight and must be driven back to the depot for load adjustment, plus the costs of any citations incurred along the way, it's possible for a truck operation to pay thousands of dollars in weighing fees a year per vehicle.

The risk of overloading can be eliminated through the use of electronic on-board weighing systems. They've been in use for more than a decade by some vocational applications, including logging, dump truck, mining, and refuse.

On-board weighing systems are now being used more frequently by the freight-hauling sector, as the costs of purchase and installation are coming down and the costs of check-weighing at commercial scales are seen as excessive.

The new generation of on-board weighing scales is easy to install, simple to use, and relatively inexpensive. And top-of-the-line models offer multiplexing capabilities, such as computer/printer interfaces and satellite communications links.

The Air-Weigh 5200 Series scale is calibrated to be accurate for all weights and gives net payload, GVW, and axle group weights. This electronic scale, which works in conjunction with the air suspension, weighs LTL shipments separately using a special tare function, and prints its own weight tickets. The 5200 allows fleets to swap trailers between tractors without recalibration and uses RS 232 ports to interface with other communications equipment.

The following models are available: a tractor-only kit; a trailer add-on kit; and a dual sensor processor kit for use on air suspensions that include both left and right height control. Optional features include a weight receipt printer package and an OmniTRACS interface cable that connects the scale to QUALCOMM's satellite communications system.

The satellite link can be used to provide a basic text message of weight receipt information. It also provides dispatch with the ability to identify and divert the closest available truck with room for the load, confirm actual weight of the shipment right at the loading site, and transmit the billing data for EDI paperless billing.

The AW 4610 is a complete tractor-trailer kit that converts air pressure in the air springs into on-the-ground weight, which is displayed in 100-lb. increments. Once calibrated, the Air-Weigh system weighs each axle group to within 200-300 lb. It takes about four hours to install the system.

The price of the AW4610 has recently been reduced to $985. The manufacturer claims that the lower price, combined with the time saved by not having to stop at scales, allows fleets to realize substantial paybacks. Air-Weigh says that many of its customers save as much as $10,000 per year per truck by maximizing payload and saving scale fees.

E-Z Weigh load monitors (manufactured by Matronic Engineering), which are suitable for tractor-trailers with air suspension, are available in 11 different configurations. When the system plugs into the air suspension, air lines connected to air pressure bags transmit the pressure to an electronic console that computes the vehicle's weight. This information is sent electronically to the digital display unit mounted in the cab or on the trailer. Systems used on trailers are weathertight.

Stewart-Warner Instrument makes a line of 100-psi air-suspended gauges designed to measure load weight on virtually any medium- or heavy-duty tractor-trailer. The gauges are suited for internal or external mounting and measure in 2-lb. increments. Typically, they are tied into a vehicle's air suspension between the height control valve and the air springs. As load weight increases, the rising air-suspension pressure registers on the gauge.

Easily visible and simple to use and maintain, Model 82396 mounts externally on the trailer and features a sealed, water- and rustproof Lexan housing. Some models, with easy-to-read analog face dials, are illuminated for internal mounting.

The original Vulcan on-board scales were developed more than a decade ago for use in the logging industry and have been particularly favored by timber, refuse, mining, and agriculture applications, as well as general trucking. The first two-wire, 12V digital system for on-board applications, the V200 meter and electronics system virtually eliminated the cable and moisture problems in the truck/trailer connector that were associated with failure in other electronic systems.

The Vulcan range now includes the V500, a four-channel electronics system using new single-line technology; fifth-wheel and single point load cells; a new center-hanger design for multi-axle suspensions; an air sensor for air-ride suspensions; and the V600, which provides an interface port to on-board printers and computers.