Whether or not a trailer is untethered or tethered to a tractor with or without a tractor-based mobile communications system, the trailer-based UTT system allows a trucking company to track a trailer's location, status, and cargo by providing the trailer's position. The trailer's position can be configured to be reported to a trucking company as often as every 2 minutes; however, as the frequency of the positioning report is increased, messaging costs increase. As a result, while en route, a tractor-trailer with a mobile communications system on the tractor typically utilizes that system for positioning information at a more cost effective rate, such as one position per hour. When the tractor-based mobile communications system is not working or available, the UTT system can track the tractor-trailer en route with more frequent updates of positions. The UTT system is a critical stand-alone location tracking system for untethered trailers.

One functionality tested in the pilot test was to capture connection and disconnection events and transmit notifications via the UTT system cellular communications to dispatchers. The event notifications provide details of the connection and disconnection event, including position, time, status, and identity data to a cellular network. This functionality was enabled through the use of a satellite-based mobile communications system on the tractor for the trailer connection and disconnection event only.

The UTT system may also be configured to establish geo-fence boundaries around individual UTT system terminals that transmit event notifications to dispatchers if the trailer violates the geo-fence. A geo-fence is an electronic boundary that a user can create to monitor trailer location and movement. Geo-fences may be created, viewed, and edited visually on a Web-based interactive map. For example, a user could locate a trailer on a map and draw a geo-fence around the trailer position by clicking and dragging a mouse. The geo-fence may be assigned to a trailer or to groups of trailers. Geo-fences may also be removed or inactivated for trailers or groups of trailers at any time.

Once the geo-fence is set and configured to provide an alert, the UTT system will send a notification to the user if the trailer crosses the geo-fence boundary. The UTT system will send an alert when a trailer exits or enters the boundary through an email or pager notification. Since the UTT system provides a trailer specific geo-fencing capability, it is unaffected by separate geo-fences of nearby trailers.

The UTT system also provides an on-board geo-fence with event-driven exception reporting. Exception-driven reporting will allow the UTT system to monitor trailer position and check for geo-fence breaks frequently, but only send a message if a geo-fence break is detected. Frequent checking for geo-fence breaks without sending frequent messages lowers messaging costs and increases battery life.

As a part of the UTT system, an ultrasonic cargo sensor detects the presence of cargo in the trailer by indicating if the trailer is unloaded or loaded. A cargo event is defined as the transition from completely unloaded to partially or completely loaded or vice-versa. The UTT system terminal wakes up to check the cargo status at a predefined frequency. Utilizing event-driven exception reporting, a status message is sent only when the cargo status changes.

As another part of the UTT system, a magnetic door sensor monitors for an open or closed door event on the trailer. A door event is defined as the transition from open to closed or from closed to open. The trailer door sensor can work in conjunction with the cargo sensor, so that only those door state changes that might affect cargo are sent to the user. For example, it is possible to configure the system to send door open events if there is cargo in the trailer and to ignore door open events if the trailer is empty. For the pilot test, only trailers with a single set of doors were monitored, and a door opening alert was sent when the trailer was loaded.

An overview of these technologies is shown in Figure 2 and described in Section 2.

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