The Short Answer
Trailer communication is challenging because an articulated vehicle combines two separate vehicle sections that need to exchange information whilst remaining capable of being repeatedly connected, disconnected and interchanged.
On a rigid vehicle, cameras, sensors and other safety equipment can remain permanently connected to the equipment receiving their information. On an articulated vehicle, that communication pathway has to cross the tractor-trailer interface and continue working as vehicle combinations change.
The challenge is therefore not simply transmitting information. A practical communication system also needs to account for vehicle interchange, the detachable physical interface, different vehicle specifications, demanding operating conditions and normal coupling procedures, whilst ensuring that information from trailer-mounted safety equipment reaches the correct tractor.
These requirements help explain why several different engineering approaches to tractor and trailer communication have developed over time.
Why Is Communication More Difficult On An Articulated Vehicle?
On a rigid vehicle, the cab and body remain part of the same permanently connected vehicle.
A rear-mounted camera, for example, can be connected to an in-cab monitor or recording system through wiring that remains in place throughout normal operation.
An articulated vehicle is fundamentally different.
The tractor and trailer are separate vehicle sections designed to be disconnected and reconnected. Any safety technology that needs to communicate across those vehicle sections therefore has to accommodate a connection that is temporary by design.
That creates an engineering challenge that does not arise in the same way on a rigid vehicle.
The Vehicles Are Designed To Separate
One of the fundamental difficulties with tractor and trailer communication is that the two sections need to communicate whilst connected, but must also remain easy to separate.
A communication pathway therefore cannot simply be treated in the same way as a permanent cable running between two points on a rigid vehicle.
It has to cross the tractor-trailer interface in a way that still allows the normal coupling and uncoupling process to take place.
Every time the combination separates, that communication relationship is broken. When another combination is formed, the relevant communication pathway needs to be available again.
The ability to disconnect is therefore not an unusual event the communication system needs to tolerate. It is a fundamental part of how the vehicle is designed to operate.
Tractors And Trailers Are Interchangeable
In many fleets, a particular tractor is not permanently assigned to a particular trailer.
A tractor may work with several trailers during a week or even during the same day, whilst an individual trailer may operate with many different tractors during its working life.
This means trailer communication cannot always be considered around one fixed vehicle combination.
Where interchangeability is required, the communication architecture needs to operate across the different combinations the fleet expects to use.
A solution that works effectively between one tractor and one trailer may become more difficult to manage if each new combination requires additional connections, configuration, pairing or driver intervention.
The challenge therefore increases as communication moves from a single vehicle pairing to a fleet-level requirement.
The Communication Pathway Has To Cross The Tractor-Trailer Interface
Safety information generated on a trailer may need to reach a monitor, warning device or recording system installed on the tractor.
That information therefore has to cross the physical interface between two independently manufactured vehicle sections.
The existing tractor-trailer connections already perform essential vehicle functions, so additional safety-system communication has to be accommodated in a way that works alongside the vehicle’s normal operation.
Engineers therefore need to determine how the information will cross that interface.
A separate physical data pathway can be introduced, information can be transmitted wirelessly, or an existing pathway can be used to carry appropriately encoded information.
Each approach addresses the same physical divide in a different way.
Vehicles And Connections Operate In A Demanding Environment
Trailer communication also has to work in the environment in which commercial vehicles actually operate.
Vehicle wiring, connectors and equipment can be exposed to vibration, movement, temperature changes, moisture, dirt and repeated coupling and uncoupling.
Components and connections therefore need to be selected, installed and protected with the operating environment in mind.
This matters because the communication pathway forms part of a working vehicle rather than a fixed installation in a controlled environment.
Reliability depends not only on how information is transmitted, but also on how the complete communication architecture performs throughout normal vehicle operation.
Mixed Fleets Add Another Layer Of Complexity
Commercial fleets are rarely made up of vehicles that are completely identical.
Tractors and trailers may come from different manufacturers, have different specifications, enter the fleet at different times and remain in service for different periods.
Safety equipment may also be added retrospectively rather than designed into the vehicle when it was originally manufactured.
A communication approach therefore needs to be considered in the context of the vehicles that actually make up the fleet, rather than one idealised tractor and trailer combination.
This becomes particularly important where fleets want compatible safety equipment to operate consistently as different vehicles are introduced, replaced or interchanged.
The System Has To Work Operationally As Well As Technically
A trailer communication system can be technically effective but still create practical difficulties if it introduces additional steps into normal fleet operation.
Where trailers change regularly, any requirement to make an additional communication connection, pair equipment, select a trailer or carry out another process has to be repeated as part of the vehicle’s operation.
The more frequently combinations change, the more important those everyday interactions become.
Communication architecture therefore needs to be considered not only in terms of whether information can be transmitted, but also how the system behaves during normal coupling, uncoupling and trailer interchange.
For a fleet, operational simplicity can be just as important as the underlying method of communication.
Safety Information Has To Reach The Correct Vehicle
Successful transmission alone is not enough. The information also has to reach the equipment associated with the correct vehicle combination.
This becomes particularly important in busy depots or yards where several equipped tractors and trailers may be operating close together.
A physical communication pathway establishes that relationship through the connected vehicle infrastructure. Wireless systems need another means of ensuring communication is established with the intended vehicle.
Different technologies address this requirement in different ways, but the objective is the same: information generated by equipment on a trailer needs to reach the tractor operating with that trailer.
Why Has Trailer Communication Become More Important?
The underlying tractor-trailer interface is not new, but the range of safety technologies that may need to communicate across it has increased.
Vehicle safety requirements have also evolved. Regulation, industry standards, accreditation schemes and individual fleet or customer requirements can all influence the safety equipment fitted to commercial vehicles.
Modern commercial vehicles can use rear and side cameras, proximity sensors, recording systems, driver warning equipment and other safety technologies.
Some of these functions are contained entirely within one vehicle section. Others require information generated on the trailer to reach equipment on the tractor.
As the range of safety technologies has developed, the communication architecture behind them has therefore become an increasingly important part of system design.
The challenge is no longer simply where a camera or sensor can be fitted. It is also how the relevant information will move between the different sections of the vehicle.
How Can Tractor And Trailer Communication Be Achieved?
There are three main engineering approaches to communicating safety information between a tractor and trailer:
- dedicated data cabling
- wireless communication
- Vehicle Safety Powerline Communication
Dedicated data cabling creates a separate physical data pathway between the relevant equipment.
Wireless communication transmits information through the air rather than through a physical data connection between the vehicle sections.
Vehicle Safety Powerline Communication uses existing OEM power wiring as the pathway over which appropriately encoded safety information is communicated.
Each approach addresses the same underlying tractor-trailer communication challenge in a different way, with different considerations for installation and operation.
Why Was Vehicle Safety Powerline Communication Developed?
Vehicle Safety Powerline Communication provides another way of addressing the difficulties created by communicating across connected or changing vehicle sections.
Rather than requiring a separate full-length data pathway between those sections or relying on wireless transmission, VSPC uses existing OEM power wiring as the communication pathway.
The existing power wiring continues to perform its normal electrical function whilst also providing the pathway over which appropriately encoded safety information is communicated.
X-Wire is SCC’s patented implementation of Vehicle Safety Powerline Communication.
In articulated applications, this allows compatible safety equipment to communicate across the tractor-trailer interface without requiring an additional data suzie for the safety-system communication pathway or wireless pairing between the connected vehicle sections.
Final Thoughts
Trailer communication is difficult because an articulated vehicle requires reliable communication between vehicle sections that are deliberately designed to separate, reconnect and interchange.
The communication pathway has to cross a detachable physical interface, operate in a demanding vehicle environment, accommodate different vehicle specifications and work within normal fleet procedures. Where vehicles are interchangeable, it also needs to continue operating as individual tractor and trailer combinations change.
Dedicated data cabling, wireless communication and Vehicle Safety Powerline Communication represent different engineering responses to those challenges.
Understanding why the challenge exists makes it easier to evaluate those approaches separately from the cameras, sensors and other safety equipment they support.
X-Wire is SCC’s patented implementation of Vehicle Safety Powerline Communication, developed to provide a consistent communication architecture for compatible safety equipment across connected or changing sections of vehicles and equipment.
