Unattended truck scales - first developed for quarrying, mining, and agriculture - are cropping up at municipal waste sites. Here's a report on what's needed to make them work, where they're performing well, and when to upgrade to one or not.

By David Engle

During the Windows-powered 1990s, weighing of garbage trucks became so automated that some waste managers began asking themselves: Do we need that scale attendant at all? The reason for discarding this person was, of course, to save on payroll - an enticing thought for cash-strapped governments. For a relatively small up-front investment in hardware and software upgrades, an occupied scale house can be transformed into an unoccupied one. "It's a no-brainer," observes Greg Barton, general manager of Compro Systems Inc., a software firm in St. Albans, WV (www.comprosystems.com). "Many times, the unattended system pays for itself in just a couple of months" by eliminating one or more full salaries indefinitely.

Cutting employees isn't always appealing, however, and waste managers who reject the wisdom of it are prone to cite the mantra "a truck scale is like a cash register" ringing up thousands in annual fees. The notion of leaving the "till" wide open without a clerk to oversee it is simply a nonstarter. As Dylan Hardy, marketing manager of scalemaker Mettler-Toledo International Inc. (www.mt.com) puts it, "So much money is tied up in a scale that many municipalities don't ever want to leave it unattended." Other strong arguments for retaining the services of the scale-house occupant include environmental laws that might require someone to inspect waste content being dumped, an expressed lack of confidence in drivers' ability or willingness to use an unattended interface, the perception that "little would actually be gained by eliminating an attendant anyway," and finally, the peace of mind in knowing that "some live person is on hand" to deal with the occasional inevitable problems.

Hence several softened versions of the "unattended" theme arise, such as the part-time-absent attendant, the dual-scale station equipped with both manned and unmanned units, and the remote-control attendant. The latter arrangement leverages the operator's oversight by adding an intercom, a Web cam, and/or a closed-circuit video to allow several stations to be overseen and monitored from afar. As Barton boasts, "We've set up systems where one of the scales is miles from the main computer, and we'll actually tie the scale-side hardware and camera systems into a company's WAN (wide area network) and transmit that (data) from miles away to a centralized point." From a single command post, a scale manager can interact with drivers via a speaker and/or view what's happening on multiple screens.

A far more common approach is to add quasi-unattended capability in order to supplement rather than replace the human operator. Typically this means installing a new, more automated scale to ease the load at a hectic landfill or transfer station without increasing staff. Still another strategy is to retrofit a site for extended operating hours in order to smooth out the traffic and eliminate early- and late-day peaks and resulting wait times. By automating nearly all of the weighing, you can assign one operator to handle the volume that used to require three or four attendants - and that operator might have time left over for doing more skill-intensive administration.

Ultimately, perhaps the determining factor on unattended configurations will be the nature of the traffic you need to process. "Unattended scales," says Barton, "are perfect wherever hauls are consistent and repetitive, where prices are set for the haul, and where data changes only minimally from haul to haul. You don't need to track anything else (for example, waste content or source data), but you just want to know how much tonnage they're bringing you on a daily basis." Thus, fully or partially unattended scales wind up being most practical at high-traffic transfer stations needing after-hours access, notes Ronnie Ricketts, sales manager at Cardinal Scale Manufacturing Company of Webb City, MO (www.cardet.com).

The least appropriate customers and application scenarios, Barton continues, are those with "lots of different haulers and companies coming in, one shot or just a few times." He also notes that if you have a lot of residential customers' trash, it's very hard to go unattended and adds that, for liability reasons, HAZMAT wastes should always be processed at attended sites. Ricketts points out, "The more complex the trash operation, the more you'll gain by improving the automation," yet greater complexity also means "you reach a point early on where a scale-house operator is necessary." He estimates that 20-25% of all his truck-scale customers are using unattended scales in various configurations.

Making the Upgrade: What You'll Need

Unattended scales operate very much like attended ones, with the major difference being that, because no operator is present, machines and software must do certain functions. An analogy might be a coin-operated automatic car wash or a walk-up ATM terminal. Typically you'll simply retrofit an existing site, perhaps when the scale is due for replacement or overhaul anyway. In order to run without any human intervention, a scale will typically need all or most of the following modifications or additions.

Access Control and Security

An entry gate will open if the arriving driver possesses, for example, an access code, a key, a "swipe" card device, an employee ID badge, or a radio-frequency (RF) or barcode reader, depending on the hardware and software selected. (However, even gate security is not absolutely necessary or universal: One remote transfer station in Florida reportedly uses an honor system.)

Site Modifications and Traffic Control

You'll need to plot out carefully how trucks will approach the scale and maneuver through the site, absent a human traffic director. Typical solutions are directional arrows or signs, red and green lights, posted instructions, routing loops, ground sensors, motion detectors, and motorized gates. Some sites must plan for scale approachways that are bidirectional - which, naturally, add to the engineering challenge. At many sites it's also common for varied trucks to be handled differently (i.e., some shunted to the attended scale, others to the unattended). This condition too will require careful forethought and planning.

As the truck rolls onto the platform, scale-mounted vehicle position sensors and remote scale displays will give the driver feedback. "A yellow light means he's not yet in position and he must realign or pull forward," notes Jim McLean, truck scales sales manager at Active Scale Manufacturing Inc. in Brantford, ON (www.activescale.com). Wheels on all axles must rest fully on the scale, of course, "with nothing hanging over," either innocently or on purpose. "A red light means he's on and being weighed; a green says he's through and may depart," he explains.

Some scales use an electric-eye beam system, not allowing weight recording until the truck's position breaks the photo eye but flashing a message, such as, "Reposition truck. Front wheel off scale." Notes Ricketts of Cardinal, "Because there's no one to tell the drivers if they're on the scale or not or if an axle is slightly off, you need to mark very, very clearly the outline of the scale to let the drivers know where they are. You should even go so far as to install siderails so that there's no way they can be off the side."

Meanwhile the gating or signaling system must ensure that only one truck approaches the scale at a time and waits patiently until others are fully cleared. Some site operators prefer loops or other gates. The latter require motors, belts, and barriers. "You're going to break these things too," McLean points out, and for this reason he prefers traffic signals. "There's less maintenance with lights. About the only thing that goes wrong with them is that you have to replace the bulb all the time." But they're relatively very cheap compared with gate components.

Also, in order to zero the scale for the next weighing, a loop detector or other sensor must be added. At a recent installation in Ontario, McLean's solution was to cut grooves into the scale's concrete approach pad and insert detectors; as a truck exits, it presses the levers, zeroing the scale and turning a traffic light green for the next hauler.

Another important element, Ricketts notes, is the overall space. "You've got to have ample staging area for people to get on and off and to clear the scales in order to park, if need be, so that the trucks behind them can get on the scale without holding things up. There's no operator out there saying, 'Hey, you go park there.' You've got to have simple instructions or lines, or whatever, indicating ample parking room."

Ricketts points out that some unattended landfills risk being hit by illegal HAZMAT or radioactive waste dumping. Several sites have protected themselves by installing surveillance cameras to take registered snapshots of every weighed load. Geiger counters can detect radioactive material and will thwart the weighing/dumping process if triggered.

Finally, if you make a mistake in positioning the driver interface or intercom poorly, notes Mettler-Toledo's Hardy, "You've got a bulls-eye there because trucks like to run into them. That's what happens most often." Some sites protect the interface from collisions by locating it away from the driveway paths. In such an approach, the driver will need to exit the cab during weighing and walk over to the interface; you might have to pour concrete sidewalks, erect a catwalk, or do other minor landscaping, notes Ricketts.

Appropriately Customized Software

Inside the personless scale house a whirring computer still resides, continuously accessing its database of registered vehicles. Software for this advanced automation is now readily available from many vendors. Your program should be both customizable and upgradable for changing needs. In fact, Charles Goen, division director for the MIS/Scales and Drop-off Division of Lake County, FL's Department of Environmental Services, believes software is probably the most critical factor in configuring an unattended scale. "Find yourself a programmer with the experience, ability, and willingness to write customized code to accomplish what you want," he advises. "(Look for) someone who will work with you almost as a beta tester because every solid waste situation from county to county is different. If you try to buy it off the shelf and then just use it without modifying it for your specific needs, you're making more work for yourself instead of less."

Scanning or Reading Devices and a Driver Interface

Profiles on each arriving truck - e.g., the identifying number, owner, route, driver, trash type, and tare weight - are typically preentered in a database. Then when the vehicle rolls past the entryway, an assortment of technologies can be used to detect the identity, such as bar-coding on fenders; an affixed RF transponder; driver-manipulated badge cards, swipe cards, and proximity cards with RF implants; or addressable key fobs (as on personal vehicles). Finally, at the low-tech end, you might opt to install numeric keypads for the drivers' manual input.

Barton says the "preferred, most automated" systems require only that the driver respond to traffic lights, which tell him that he is successfully logged on to the system (such as via the RF signal). "He pulls up to the scale, is weighed, logs his load, and goes on his way. He can be on and off the scale in 15 or 20 seconds. It's very efficient."

A variation here might include the display of the trucks identifying information on a screen, such as "You are vehicle XYZ, carrying such-and-such waste." The driver would then confirm the accuracy by punching Enter, keying in a two-letter code to alter or record the load type, or responding to an "A" or "B" option. Then he would await the transaction ticket output.

If you're evaluating the tradeoffs of using RF-embedded cards versus bar-coded trucks versus manual driver input, and so on, you should note that, as Gary Zoerner of Sarasota, FL's solid waste office tells us,  it is relatively easy for a driver to associate the wrong card with the wrong truck or load. Also, some municipalities reportedly have had serious trouble with RF transponders in environments with high-magnetic fields (as in some transfer stations with scrap metal processors) or when the transponders are subjected to the punishing impact of rolloff debris. On the other side of the issue, however, four users of RF transponders in Canada - including Active Scale's McLean and the City of Toronto - report that RF signalers are quite reliable. It would seem that the method for automated data input might face differing vulnerabilities, depending on the specific environment.

Several of the sources we talked to strongly agreed with Goen's general advice to keep the automation as simple as possible, meaning, "The less human intervention the better." When Lake County first installed its unattended scale, drivers had to begin the weighing process by touching a credit-card–size RF transponder on the interface. "(Next) the readout prompter would ask him for a source code, material code, customer code, and all this other stuff," he recalls. Even this basic interaction was problematic. "So we went and laminated all the two-digit codes on all the cards and gave these to the drivers. All they had to do was punch the codes in. They could use these cards for multiple routes and multiple commodities. I'm telling you that was way too much." Over time, the data-entry procedure was streamlined and simplified so that all load and route information was preentered. "All the driver has to do is make sure he grabs the right card for the route that he's delivering," says Goen. Automation has once again made life much easier.

Contingency Planning

What happens if the unattended scale fails? Or if a heavy rainstorm leaves you doubting whether it's still on-line? You need to prepare backup procedures in order to minimize any potential loss of revenue or downtime. For example, Lake County decided that if a particular truck's weight and load aren't properly recorded at the scale (for whatever reason), a substitute value based on historical averages for that truck and route would be acceptable to both parties. At nearby Sarasota County, Zoerner installed an intercom phone to handle trouble calls, and later (after a truck collision wiped out the phone) simply posted his office number. "Problems are inevitable but not insurmountable," he says.

Driver Training

Dealing with an automatic system isn't particularly difficult, but it does require that some orientation course be given to each current and future driver. A certain level of sophistication and comfort with modern technology helps, but unfortunately, observes Hardy, "Not everybody is fully up the curve on the latest tech and software systems that interact with unattended solutions. So resistance is there as well." One vendor told us that a scale with a cumbersome interface suffered repeated vandalism from drivers "who couldn't cope with it." Ricketts agrees. "If a driver gets flustered, a line starts to form and drivers will drive off. The city will be losing revenue." Hence, his advice: "Keep it very, very simple for them."

Following each new installation, Cardinal likes to conduct training classes not only for the scale department employees but also for all the drivers and other selected stalwarts. The latter will then take responsibility for the ongoing updates and follow-through with future staff. If scores of drivers are working multiple shifts, schooling might require a full week initially, notes Ricketts. Naturally your course should give heavy emphasis to what to do if things go wrong.

When drivers are expected to interface with machines instead of people, the combination of simplicity, full automation, and good training will be critical to your success.

Scheduled Maintenance Visits

Since an attendant might not be present, someone must do routine periodic visits, if only to change the printer paper. To avoid someone making a special trip, maintenance can be dovetailed with the handling of a trouble call.

Take note, too, of the impact from inclement weather. McLean points out that an unmanned pit scale, following a heavy rainstorm, "may require someone to look down the hatch and, if water has accumulated, to pump it out." This work and other enclosed-space or potential methane gas exposure might necessitate additional training for OSHA safety compliance.

Systems Implementation

How are these unmanned systems being implemented in the real world? For a look, here are several cases studies.

The Cities of Hamilton and London, ON

Active Scale has installed unattended systems for several Canadian cities, and when we talked to sales manager Jim McLean in mid-2003, the firm was in the throes of designing one for the city of Hamilton's landfill. It will weigh the anticipated light traffic load from 25-50 franchise trucks arriving daily from a transfer station. "The general public doesn't come here," notes McLean.

High-level automation was the overriding design priority. RF transponders on each truck will signal the identity, serial number, and gross and tare weights and allow gate access; drivers will merely key in their specific waste material for the load. Correct alignment for weighing is ensured by gates, which respond to position sensors.

The scale's software was custom-designed by PC Automation of Toronto (www.pcauto.com; for more on this firm, see "Ultimate Software: What Are Available, What They Will Do" in the July/August 2003 issue). Tare weights and other data on each vehicle are preentered, eliminating the need for outbound weighing; on occasion, however, the driver's interface will display a message to "update your tare weight" on a future visit.

Nearby, for the city of London in southern Ontario, Active Scale also upgraded two archaic scales long overdue for replacement, adding components for unattended use. A primary goal, says Wesley Abbott, manager of waste disposal special projects for the city, was to extend the station's hours of operation in order to relieve the strain on a busy scale house. You can make one employee much more productive and efficient with the addition of these unattended automation features, he says.

Based on several years of operational experience in the unattended mode, Abbott's tip to other would-be implementers is to think through how different vehicles are going to flow at your facility, especially if you'll be processing them at both attended and unattended scales. The task of directing traffic becomes even more complicated when, for example, a light signals green or red to indicate a truck's weighing status - while a gate system is simultaneously opening and closing. On initial trials at the London landfill, some drivers were pulling forward when a gate rose but hesitating at the scale's red light - apparently not grasping the indicator's meaning. "You have to give it lots of thought as to when a signal is triggered and when it is not," Abbott emphasizes.

Sarasota County, FL

Sarasota operates two unattended scales - one at a transfer station taking in only a few dozen trucks a day, and a second at a landfill handling 75-100 vehicles daily, where it's paired with an attended version. Both of the unattended scales receive only regular or recurring accounts, those being city residential trash trucks from North Port and Venice and a fleet of 40 Waste Management trucks franchised for either residential or construction waste. On all of these repeat customers, a database has stored the preentered tare weights and truck ID numbers, and the trucks are bar-coded on side fenders. As each vehicle approaches the scale, ground sensors open and close gates to control the traffic flow. A scanner reads the bar code. Drivers pull forward slowly to arrive at an interface box, which flashes the ID number that was just scanned. When prompted, the driver taps a keypad to confirm the correct reading and, in some cases, is given an "A" or "B" option to indicate the specific load type for that day - for example, residential trash or rolloff waste. Once weighing is completed, the interface issues a transaction ticket, and the driver is on his way, describes Gary Zoerner, senior account administrator for Sarasota's Central County Solid Waste Disposal Complex.

Farther south, the county's remote, wholly unattended transfer-station scale has no gate security; there's only limited traffic to control. Drivers proceed slowly between barricades in order to mount the scale platform. Zoerner notes that a few collisions have knocked the scale off its pins or occasionally bumped and damaged the barcode scanner.

As for the decision to go unattended, considering that the station receives only light volume, "We really didn't have much choice," Zoerner remarks. "It would have been a scheduling and monetary nightmare to put an attendant down there. So an unattended scale really was the answer. It allowed us to use an old existing facility (a defunct landfill) which we could continue to get some use out of and save the taxpayers' money."

Regarding operational stability, Zoerner reports that basically everything works fine now but concedes that an assortment of problems plagued the scales several years ago. One major headache was a very slow dot-matrix printer churning out transaction tickets. Impatient drivers would tear off the sheets before the printer was done, causing jams and sometimes disabling the system for hours. Also, characters painted on a numeric keypad tended to wear out quickly due to repeated use or abuse. Ultimately Zoerner replaced the pad with a very quick touch-screen interface and installed a thermal-paper printer similar to those at ATMs. This combination solved most of the problems. "It's nice, clean, neat, and fast" - with total processing time well under two minutes per vehicle, he says. "For the most part, everybody is quite happy with it."

Mishaps still occur two or three times a week at the fully unattended site. When they do come up, the driver calls a trouble number emblazoned on the interface; problems are usually easily fixable. For example, the scale-house computer sometimes freezes up due to drivers excessively hitting the Enter button and/or unresolved software glitches. This or other problems necessitate that Zoerner drive 10 mi. from his office to fix them. "When it's down, it's a pain, and it always will be a pain," he admits. Even so, the system has paid for itself in the first year in labor alone, he maintains. On the whole, unattended operation at both sites "has been awesome and great for saving manpower." The fully automated scale at the landfill "also saves us from having a long, long line during peak parts of day - the first thing in the morning, at the lunch hour, and in a last spurt around 4 p.m." Having an attended scale nearby at the landfill also makes it easy for the operator to fix any problems.

Zoerner's tip to would-be adopters: If you're using a video monitor display interface, consider the effect of bright sunlight, which can make screens unreadable. He points out that installing shade hoods or awnings may be precluded if the truck must pull up close.

Lake County, FL

Unlike nearby Sarasota, this central Florida county wasn't looking to save on a scale attendant so much as trying to moderate rush-hour spikes causing long wait times at the tipping floor, says Lake County's Goen. Scales at the busy landfill and incinerator are manned from 7:30 a.m. to 5:30 p.m. daily. Automating them for unattended access during early-dawn and nighttime hours has boosted efficiency and productivity, he says. "Instead of cramming all the tonnage into a daytime hour block, we can spread it out." During the attended portion of the day, processing can be either fully automated by the system or fully attended by the weighmaster.

Thanks to the new automation features installed two years ago (and still being honed operationally), average waiting time for the franchise haulers and municipal trucks has been shaved from its original 25- to 40-minute delay per visit, down to only seven to 10 minutes.

Lake County's configuration of the unattended scale technology was typical: The routine data on residential trash carriers (three franchises) were preentered into the database; the information seldom varies in load content or routes. Drivers then were issued plastic cards with RF signalers encoded with their route profile. Some who drive multiple routes in different trucks were given multiple cards (which they must keep properly sorted out on their own). At the facility gate, drivers touch the card to an RF reader to gain access and initiate the weighing sequence. Goen's tip on issuing costly swipe cards or RF transponders and so on: "Don't given them to individual drivers but to a single person, such as a supervising route manager, who will be responsible for their inventory and correct use." Then if cards are lost or abused, you can charge the hauler for the replacement.

Goen sums up with a piece of advice that perhaps best expresses why transfer stations that are largely automated to offer extended hours of access are certain to grow in appeal: "The more you keep trucks out on their route, the better it is. You don't want them bunched up at the scales."

La Mesa, CA–based writer David Engle specializes in construction-related topics.

MSW - September/October 2003