Location may be everything in real estate, but when it comes to trailer tracking, it's just a starting point. As important as it is to collect updated position reports from the trailers in your fleet, these systems are actually a communications channel, and location is just the initial information being relayed over that channel. As many are finding out, the real value of a trailer tracking system lies in exploiting that communications channel to deliver a wide range of information.

“Our initial view of a new technology's value is always narrow at the onset,” says Dr. Joseph Salvo, manager of the Pervasive Decisioning Systems Laboratory at GE Global Research. Trucking is still in the process of defining how it will use trailer tracking, but the potential is there “to make trailer systems not just a tracking device, but a real window into logistics operations,” says Salvo.

The key to realizing that potential is filling the communications channel with useful information. Capturing that information will require a wide range of sensors that are inexpensive enough to install on large numbers of trailers, flexible enough to accommodate a variety of operations and equipment types, and reliable enough to provide trustworthy data.

Currently there are four types of sensors available with most trailer tracking systems on the market: a cargo sensor that indicates whether or not a trailer is loaded; a hook/unhook senor that can tell if a trailer has been picked up or dropped; a door-opening sensor, and a motion sensor that can determine if a trailer starts to move.


All of the cargo sensors now available use ultrasonic or acoustic waves to determine trailer status, returning a loaded signal if they detect an object as small as a 4-ft. sq. cube. They are relatively low in cost and, more importantly, drain little power from the tracking system's limited battery life.

Although they're proving useful in truckload-type operations, the ultrasonic devices do have a number of drawbacks. They are not accurate enough to measure available capacity on a partially loaded trailer, and they have to be tuned to fit differences in trailer materials and construction. Also, accuracy is affected by changes in temperature, humidity and distance from the sensor, leading some designs to measure only the front 20 feet of a trailer to determine loaded status.

New technologies, however, promise to improve cargo-sensor accuracy without compromising power consumption or cost. Within the month, the GE Veriwise system is expected to introduce a cargo sensor that projects infrared lines down the entire length of a trailer looking for objects. The main benefits of infrared are that it's unaffected by temperature and humidity, and is accurate for longer distances. GE has also demonstrated a camera link that offers a snapshot of the trailer's interior.

TransCore says it will also introduce a new, more accurate cargo sensor for its GlobalWave system later this year. Although unwilling to provide details at this point, Dave Sward, GM of the GlobalWave products, says it will not be an ultrasonic or acoustic device.

Further out, a new technology called “ultra-wideband” could provide highly accurate data on a trailer's load, according to Craig Boddy, vp-mobile asset tracking for Teletouch, which offers two different trailer tracking systems. Actually under development as an extremely low-power, short-range wireless communications technology, ultra-wideband could also be used to fill a trailer with energy that could be read much like radar, says Boddy.

The hardware for door sensors is much simpler, using a magnetic or contact switch to detect a trailer door opening. The difficulty is figuring out how to use that information. In fact, most trailer tracking providers say they offer door sensors because prospective customers always ask about them, although very few actually install them once they've decided to set up a tracking system.


“We find that most customers initially say they want to know when trailer doors are opened,” says Sward. “But in practice, doors are opened a lot, and the challenge becomes determining the difference between a routine opening and a significant one.”

The most practical use for door sensors at this point is with high-value cargo moving in sealed trailers, since any opening would be significant. If a system allows over-the-air programming, some fleets are ordering door sensors and turning them on only when a trailer is carrying such a load, Sward adds.

Similarly, hook/unhook sensors are simple magnetic switches placed near the kingpin that are only valuable if a fleet can figure out a way to sort and filter that information. Knowing when or where a trailer is picked up or dropped has great potential value in many operations, but it requires a good deal of back-office work to realize that potential.

The value of the fourth common sensor, a motion detector, isn't always as readily apparent to many fleets. Sometimes built right into the tracking unit itself, a motion detector is the only practical way battery-powered systems can offer geofencing on a timely basis.

There's a common misconception that a trailer system will immediately send out an alert if it enters or leaves an area established as a geofence by the fleet, says Boddy.

All units actually calculate their own position using signals from the GPS systems or acquire some information from the GPS signals. That information then has to be transmitted over a wireless network to a host system. Waking up the unit to determine location and to transmit it consumes battery power, so under normal circumstances most fleets limit position reports to once or twice a day. That means a fleet won't be told a trailer has crossed a geofence until that scheduled transmission.

By turning on the unit if it senses movement for a predetermined period, the motion detector brings geofence alerts closer to real-time, at least if a trailer is supposed to be parked. At that point, a fleet can determine whether the movement is a legitimate one.

Despite their availability, use of these four sensor types, either singly or in combination, is still fairly low, according to system providers. Part of the reason is the added cost, but a broader explanation is that many fleets are still struggling with how to find value in the information trailer sensors provide.

“The benefit [from wireless communications] comes from turning [vehicle] data into information a fleet can act on,” says Mike Brown, vp-marketing for Aether Systems, which offers two different trailer tracking systems.

Figuring out how to extract that benefit isn't always immediately obvious. “A door opening alert tells you one thing, but if [the system] tells you it's opening in the wrong place, that tells you something much more valuable,” says Brown.

And if you combine that information with a dispatch system, “you now know who's suppose to be picking up that trailer, what route it's supposed to be taking, what moves are prohibited and so on,” he says. “Now you have the information to determine if that door opening is inconsistent with what should be happening.”

Add in other systems already on the trailer, and sensors begin to offer an even more complex information matrix. For example, Terion's system and a hook/unhook sensor linked to the PLC multiplex communications networks found on newer trailers “can send you the ID for the tractor that just picked up that trailer,” says Todd Felker, Terion vp-sales and marketing. The fleet's dispatch system can use that information to make sure the right tractor has picked up the right trailer and send out an immediate alert if there's a mistake. “You've got a hook/unhook on steroids,” says Felker.

The same principle is used by resellers of the GlobalWave system to integrate it with refrigeration unit electronics for remote access to reefer unit monitors, controls and diagnostics.

A broad range of new sensors nearing commercial release can only increase the importance of having some type of wireless communications channel on trailers. Links for tire-pressure monitoring are likely to be available for most systems in the near future, as are at least basic temperature sensors. And specialized sensors for niche applications are not far behind.

SkyBitz, for example, is not only getting ready to release cargo temperature sensors, but it will also soon offer interfaces for both tire inflation monitors and engine controllers, says Roni Taylor, executive vp-marketing. Working with the government on security demonstration projects, it has also already run field tests with both nuclear material and intrusion sensors for marine cargo containers that can communicate even from deep within a ship's cargo hold over wireless local area networks.

But perhaps the most interesting of the new sensors under development are RFID readers. With Wal-Mart, the Dept. of Defense and other major consumers of trucking services now pushing for routine use of RFID, marrying RFID readers with wireless tracking will allow trailer systems to create manifests as trailers are loaded or unloaded, and transmit that information back to fleets and their customers. GE has already publicly demonstrated an integrated RFID/trailer-tracking unit, and all the other providers say they are working on similar systems.

“In the trailer environment, RFID is a natural fit,” says Brown. “It may not be the next step [in sensors], but everyone can see the value in knowing what's loaded in a trailer at what location.”

Combined with the other sensors both currently available and in development, RFID capability would certainly make it easier to see the real value of trailer tracking as the most aggressive fleet operations attempt to claim to a central role in the development of true supply chain visibility.