Collision warning systems (CWS) and collision mitigation electronics (CME) are becoming increasingly used in highway trucks, spec’d by operators who are determined to keep operational costs and downtime to a minimum in an increasingly competitive environment. Fleet operators are finding both these technologies to be cost effective with ROI coming sooner than forecast. CME includes technologies such as antilock braking systems (ABS), automatic traction control (ATC), anti-rollover electronics (ARE), and directional stability control (DSC) systems. CME transactions are mainly electronic and make use of the multiplexing capability of the chassis data. Any module with an address on the data bus can be involved in a CME event.

While CME functions to a large extent without driver intervention, most CWS require driver intervention as some point during the progress of a collision avoidance event. Both these technologies have introduced a range of new terms into the language of trucking. This newsletter will focus on CWS and serve as a primer in some of the terms recommended by the TMC. Some of the currently available types of system will be defined, followed by a description of the technology that enables each system to function.

The following CWS are available in highway trucks today:

Headway alert (HAS) – feeds back info to the driver for maintaining a safe following distance to the nearest in-the-path vehicle: that is a vehicle traveling in the same direction and same lane as the truck. HAS is an anti-tailgating system and in automobiles may provide intervention strategies (such as braking the vehicle) when a programmed threshold of distance/speed is breached. Currently in truck applications these are alert-only devices.

Forward collision warning systems (FCWS) – these may use the same detection technologies as HAS but the alert is produced to the operator (as opposed to the data bus) when an imminent collision is projected. They function through a range of 2 meters (7 feet) up to around 200 meters (650 feet). The alert is designed to prompt immediate driver intervention to avoid a collision. Once again, this management of this technology used in automobiles is more likely to be interventionary, that is, capable of aggressive braking.

Blind spot systems (BSS) – provides data located in the blind spot of the vehicle, typically other vehicles traveling at some velocity in an adjacent lane to the truck’s direction of travel. May also be effective as a parking assist. The range is usually 0 to 4 meters (13 feet). BSS is an add-on to an Eaton VORAD system.

Back-up aid system (BAS) – signals data to the driver about objects in the path of a back-up direction while the vehicle is being reversed. While cameras have been used for many years in such applications as school buses and garbage vehicles, these are not considered as BAS. A true BAS uses video technology to produce a video image, along with both a video and audio alert if the back-up is detected as having danger potential.

Lane departure warning system (LDWS) – warns the driver when the vehicle unintentionally departs the lane of forward travel. Intended and unintended lane departures are defined by whether the turn signals are active when a lane transgression takes place. A video camera and processing electronics are usually required to enable a typical LDWS. System accuracy depends on the precision to which the camera has mounted and set up.

To enable CWS technologies, the following electronic technologies are required:

• RADAR (radio detection and ranging) – a radar system transmits streams of RF pulses and detects echo signals bounced from objects in the stream path. Radar is precise and has all-weather capability. It is the enabling technology behind Eaton’s VORAD system. Radar uses frequency shift analysis to accurately determine the velocity of moving objects and this can be undertaken using low level microprocessors.

• LIDAR – (light detection and ranging). A Lidar system transmits light, usually laser beams, and senses reflected light to determine distance. Lidar cannot measure an object’s speed because there is no Doppler shift in light waves. However, with high power computer processing capability, lidar can be used to calculate the virtual velocity of a moving object. The computing power is provided by a new generation of economical programmable logic controllers (PLCs) which pack dense processing capability into minute packages. A disadvantage of Lidar is reduced all-weather capability, so heavy rain and road spray can neutralize the system.

• Ultrasonic – ultrasonic sensors operate with sound waves that fall just outside the range of human hearing. An ultrasonic system transmits high frequency sound waves and senses reflected sound waves. Cannot be used to detect an object’s velocity because sound waves attenuate (decrease in strength) due to atmospheric friction. This wave attenuation also limits the detection range to 10 meters or less. Used in blind spot and back-up aids but not for HAS or FCWS.

• Infrared – these track the heat signature of a target object in order to differentiate it from its surroundings. The heat sensitivity has greatly improved over the past decade so that temperature differences of as little as 2 degrees Fahrenheit can be detected. Current infrared systems are capable of distinguishing light reflecting tape from the background it is pasted onto.

• Vision – we know this as ‘camera’ technology. Because of the recent introduction of low cost, powerful PLCs (see entry under Lidar), vision electronics are becoming common on today’s automobiles. Vision-driven systems use imager engines similar to what you might find in a digital camera. The quality of the imager combined with PLC processing potency enables the system to calculate factors such as relative velocity. Like Lidar, vision-driven systems are lose functionality in poor weather and high spray/splash conditions but they are lower in cost and potentially more comprehensive that its competitor systems.

Most of these collision avoidance systems are virtually maintenance free though the ‘eye’ (viz camera lens) on the two vision driven systems must be kept free of road dirt, salt and de-icing brine. High end systems offer an improved machine-human interface. The machine-human interface includes visual display monitors, LED displays, and audio alerts. Most of the current technologies in truck applications provide audit trails to re-enact event profiles. In some cases, the software may perform some basic crash analyses in the event the alerts did not succeed. This has led to the use of the slightly misleading term black box to describe CWS driver modules.

Sean Bennett February 2010

The terms and acronyms used in this newsletter are consistent with those proposed by TMC RP430 A.