As technicians, we have become familiar with the passive safety features in automobiles. The changes have focused on improved structural designs and crumple zones along with deformable steering wheels to protect the passengers inside of the vehicle in the event of a collision. Restraint systems have also evolved with items such as smart airbags, passenger presence systems and safety belt pretensioners.
Intelligent restraints systems are able to adjust their activity based on the severity of an accident and an entire book could be written on that subject alone, but this article will focus on the systems that are installed to try to avoid an accident in the first place.
The biggest cause of accidents
The biggest factor in accidents is the human factor. Studies have shown that 65 percent to 70 percent of accidents are due to human failures, 20 to 30 percent by environmental conditions and the remaining small percentage are due to actual mechanical failures. You may have noticed a change in the cabin design of modern vehicles with a heavy focus on the ergonomics of the driver. This is just what it first appears to be – an effort in improving driver comfort. Studies have shown that the more comfortable a driver is in their vehicle, the faster they will react to a pending accident scenario. So there is a direct relationship between driver comfort and vehicle safety.
However, how comfortable is too comfortable? When vehicles come equipped with heated and cooled seats, some with massagers, exhausted and fatigued drivers may tend to fall asleep on the road. It is estimated by the National Highway Traffic Safety Administration (NHSTA) that 2.5 percent of fatal crashes and 2 percent of collisions with injury occur due to drivers who are drowsy.
While all safety systems monitor the vehicle’s parameters, there is one that monitors the driver’s. What’s that little coffee cup icon on the dash of newer Mercedes-Benz vehicles, for example? That symbol means that the Attention Assist safety feature of the vehicle is active. This system monitors the driver and alerts them when they show signs of drowsiness and fatigue. During the beginning moments of the journey, the system creates a profile of the driver’s style (referred to as driver modeling) and then it is used as a reference to monitor changes over time. Tired drivers tend to make minor steering corrections; the system uses the steering angle sensor to monitor steering wheel movement and steering speed. Next the system compares other inputs such as:
· How long has the driver been at the wheel
· Is the operator using devices such as the turn signals, radio inputs or HVAC control, which shows signs of awareness
· External conditions such as crosswinds and rough roads are also monitored to determine if those might be affecting the driver’s actions
If the system determines that the driver is showing signs of drowsiness, a large coffee cup icon (different from the one little icon on the dash) appears on the display, along with an audible tone informing the driver they need to take break.
Vehicles are continuing to use driver modeling to adapt collision avoidance systems to the behavior of the operator. Some factors include the driver’s emotional state, fatigue level, risk acceptance level and driving style (normal, defensive or aggressive). In this way, vehicles are becoming more personalized and can use these inputs when determining a pre-crash condition.
What is a pre-crash condition? By using various cameras, radar and sensors to determine an obstacle’s distance and approaching velocity, a safety module can determine when a crash is imminent and activate the safety devices milliseconds before the impact occurs. For example, pre-crash airbags are larger than standard airbags by nearly 30 percent. By using a profile of the driver, referred to as occupant kinematics, the airbag will be fully inflated by the time the driver moves forward in response to the impact, thus transferring the velocity the driver imparts on the narrow seatbelt to the airbag and its larger surface area. One other benefit is that since the airbag has more time to inflate by being triggered before impact, the velocity that is deployed can be reduced.
Overview of collision avoidance systems
Antilock brakes (ABS) are standard on vehicles sold today, but there are several other systems that work in conjunction with ABS features to help control a vehicle during critical situations.
Brake Assist System (BAS)
This system detects the velocity the brake pedal is depressed to determine the severity of the stop. For as long as the driver holds the brake pedal, the brake system pressure is increased until the wheel speed reaches potential lockup and activation of the ABS system occurs. When the brake pedal pressure is reduced, normal brake system pressure is restored all without the driver ever being aware of the system’s activation.
Automatic Braking Assist
Automatic Braking Assist automatically applies the brakes without input from the driver. This system activates when the collision is unavoidable and the driver has not responded fast enough to the situation. This helps to lessen the severity of the impact. In a low-speed situation, the system may help to avoid the crash altogether. This system can also work in conjunction with the Adaptive Cruise Control system to reduce the vehicle’s speed when it approaches a slower moving vehicle.
Electronic Stability Control (ESC)
Able to detect when a vehicle is about to skid out of control, the ESC system stabilizes the vehicle while cornering. This system uses its main inputs from the steering angle sensor and wheel speed sensors along with inputs from a yaw rate sensor and a lateral acceleration sensor. The system is able to calculate and compensate for both oversteer and understeer conditions. For example, if a vehicle was going too fast into a right-hand turn and the ESC system detected an oversteer condition, where the rear of the vehicle was about to swing outwards, the brake would be applied slightly to the rear wheel on the inside of the curve, in this case the RR and simultaneously the PCM would reduce engine power to bring the vehicle back under control. The driver may or may not notice a skid control symbol on the driver information display, depending on the manufacturer.
Adaptive Front Lighting (AFS)
When most of us think about collision avoidance systems, seldom do we think about the headlights. However, adaptive headlights play a major role in vehicle safety. Xenon headlamps with dynamic cornering lights improve illumination of corners nearly 90 percent. At driving speeds of 10 mph or greater, the headlamps are swiveled in the same direction as the steering wheel up to a maximum of 15 percent. Inputs used by this system are the steering angle and vehicle speed.
Another amazing feature of the AFS system is the ability to adapt to current driving conditions. For example when driving at lower speeds as in city driving, the headlamps are lowered and aimed apart from each other to improve close range visibility. During highway driving, the headlamps are moved closer together and aimed higher to increase the distance visible to the driver.
When turning the steering wheel, the headlight cone expands up to 35 degrees to illuminate objects in the roadway. This can be activated by either a predetermined amount of steering wheel movement in the direction of travel or activation of the turn signal switch.
Ask someone who rides a motorcycle and they will tell you if there is an object in the road you want to avoid contact with, don’t focus your sights directly on it because you will end up hitting it. Instead, you want to focus on an escape path to avoid the object. There is a system that, when a potential collision has been predisposed, at an intersection for example, changes the illuminated area of the headlights and intensifies the brightness on the rear of the vehicle that has just crossed in front of them. The driver will instinctively focus on the bright area and steer towards it, avoiding a collision instead of continuing directly into the cross traffic.
Adaptive Cruise Control (ACC)
Using radar, this system is activated by the driver. Speed is set and so is the distance to the vehicle in front, then the system automatically adjusts itself to the preselected parameters. When the vehicle in front slows, or when approaching a slower vehicle, speed is automatically adjusted by the electronic throttle control and/or limited automatic braking. When there is no vehicle in front, the preset speed is maintained.
Lateral Guidance Systems
Side assist is used to warn drivers of approaching vehicles when attempting a lane change. Warning lamps are sometimes located on the side-view mirrors to help the driver detect vehicles in their potential blind spot. The system also is sensitive enough not to set off a warning for vehicles more than one lane away. However, systems are usually only active at speeds above approximately 40 mph, like regular cruise control systems, so it will not be of assistance in city driving.
Another variation of the Lateral Guidance System is a type of lane assist, referred to as Lane Departure Warning that monitors the vehicle’s ability to stay in the desired lane. A Front View Camera Module is located in the same location as the rearview mirror behind the windshield. The camera is also used for forward collision monitoring and alert systems. Most can detect lane markings at a distance of approximately 200 ft. The vehicle’s position in the lane is displayed to the driver on the information display or the instrument cluster. When the vehicle starts to drift out of its lane, a minute correctional steering adjustment is made, which is also noticed by the driver. On Cadillacs with Active Safety Seats, a set of vibratory pulses is also sent to the same side of the seat as the lane that has been crossed. Some instances will not give a warning to the driver when changing lanes, these include: using a turn signal, an intentional lane change and changing lanes while accelerating or braking.
A warning message will be displayed if the camera cannot detect lane markings due to not being present, rain, snow, etc. or when the camera lens is blocked by dirt, fog or damage to the windshield.
The Lane Departure Warning System can be deactivated by the driver is desired.
Parking Assist Systems
This system uses ultrasonic sensors mounted to the rear and sometimes the front bumpers (2-6 on each) to estimate distance of nearby objects. The sensors emit a frequency that bounces off the object and back to the sensor. The time it takes for the signal reach the object and return to the sensor correlates to the distance of the object. This measurement is referred to as echo time.
There are even some systems that self park. They automatically calculate and adjust the steering for reverse parallel parking maneuvers, while the driver is still in control of the accelerator pedal.
Most vehicles have an on/off or a deactivation switch for the park assist systems, especially the ones that automatically turn on during low speed driving. I often wondered why someone would want to turn off a safety feature, that is until I drove through a carwash with an active system. The audible dings and flashing lights on the display caused by the rotating brushes mimic that of a Las Vegas casino.
Active Safety Seats
These are an alert feature controlled by the memory seat module used on some newer Cadillac and GM driver seats. It activates a haptic (vibratory) alert when a situation occurs that requires the driver’s attention. It can be used with parking assistance, lane departure warning and crash mitigation. The system can even send pulses to only the side of the seat that the danger is on so the driver can react more quickly. The first time I experienced this was when backing up close to a vehicle behind me on my right. I was not familiar with this system yet and thought I ran over something and it was vibrating against the floor pan of the vehicle.
Night Assist Systems
A study has shown that only one fourth of drivers use their high beam headlights when the situation allows them to. There are a couple of different systems available on modern vehicles. First is the Night Vision system, which records the area in front of a vehicle using a camera usually mounted on the windshield or rearview mirror assembly. Passive Night Vision systems make use of a thermal imaging camera that identifies sources of heat, such as animals, pedestrians and other vehicles. The image is shown on a display unit or in the instrument cluster. However, objects that have the same temperature as the road surface will not be detected and the driver will not be alerted to their presence in the road.
Active Night Vision Systems differ because the entire area in front of the vehicle is illuminated so the driver display shows an almost daytime image of the road. This system uses an Infrared light to illuminate the frontal view of the vehicle, which is then reflected back to a normal vehicle camera and shown on the display area.
Lastly, the High Beam Assistance System uses a camera to watch vehicles both in front of the driver and oncoming traffic, then proceeds to adapt the headlights to the situation. There are several versions of this system. The basic system simply switches high beams on and off according to surrounding/oncoming traffic. An approximate range for turning the high beams off is when a vehicle in front is less than 1,300 ft. away or oncoming traffic is less than 3,300 ft. away.
A second version adapts the high beams vertically so that a driver’s field of view is extended while detecting the position of the vehicle in front.
A third version also adapts the lights horizontally so that the intensity of the beam is dimmed to oncoming traffic but maintains higher intensity on the dark areas to the side of the road that may not be immediately visible with normal low-beam headlamps. This system also improves visibility for other drivers, both oncoming and preceding by illuminating more of the dark areas that may have been difficult to see if regular high beams were used.
Some park assist systems utilize a rear view camera which shows the trajectory of the vehicle corresponding to the steering sensor input.
[Rearview parking assist while turning steering wheel right]
Thinking into the future, the advanced lighting modules will correlate data with the navigation system to have a type of predictive lighting that will be able to anticipate the curvature of the road. The system will swivel the cornering light before the steering wheel is even turned so the driver will notice objects sooner and have more time to react, if needed.
A look behind
NHTSA has announced that all vehicles under 10,000 lbs. shall require a rearview backup camera as of May 1, 2018. Since many vehicles have had rear cameras for several model years, this may be one of the more common repairs technicians will see today. Keep in mind that rearview cameras may not display or have a distorted display on the monitor due to:
• Outdoor elements such as rain, ice, snow or mud
• Nighttime conditions or poorly lighted areas
• Glare from bright sunlight or high-beam headlights
• Very high temperatures
• Objects mounted to the rear of the vehicle, such as bicycle racks
One of my first experiences was with a 2011 Ford Edge. The customer complaint is that sometimes the rearview image appears upside down and other times, not at all. For system diagnostics, a scan tool capable of communicating with the enhanced system, in this Ford’s case it was the Accessory Protocol Interface Module (APIM), is usually the first step. Sure enough, a Code C1001 Vision System Camera error is shown. The diagnostics for this code are pretty straightforward with some basic voltage and continuity checks confirming the defective camera. I did notice after replacing the rearview camera that the picture was much clearer. The glass cover, in some cases lenses, are exposed to the elements and do take a beating over time. Note that I did clean the lens before taking the picture of the upside down image, but it still has a hazy look compared to the image displayed by the new camera.
Many collision avoidance systems also present another challenge to technicians, which is programming and calibration. Several manufacturers require special tools, such as aiming targets to calibrate the system, but other items, like the rearview camera on the Ford Edge, was plug and play.
For the all systems, it is a must to check information systems for when a calibration procedure or special tooling is required. For example, on a 2013 Cadillac ATS with a windshield that had just been replaced, as it turns out calibration for this model was only required if the camera module was replaced. As long as the original camera is correctly mounted, no calibration is needed. Calibration is also not required if the original camera module was reprogrammed.
However, the calibration process is straightforward, which consists of completing a short drive cycle (3-15 minutes) on a road with visible lane markings at speeds between 35-56 mph. Of course, stop-and-go traffic, curvy roads, faded lane markings and other environmental conditions can cause a longer drive cycle to complete the calibration process. The process is complete when the amber Lane Departure Warning indicator turns off and then the green Ready to Assist indicator will illuminate.
[upside down image displayed by defective camera]
This is a likely image you will encounter when a camera becomes defective. Notice the degradation of the image on the old camera compared to a new one. The lenses are exposed to environmental conditions and become scratched. The lens was cleaned before the picture was taken.
how the camera sits in the holder
Notice that the small camera still uses 6 different wires at the connector; this is a more complicated device than most would imagine.
