Health & Safety
Vehicle Safety TechnologyYear on year the reported number of road casualties in the UK decreases and we now have some of the safest roads in the world. Vehicle manufacturers and system suppliers are developing advanced safety systems at incredibly fast rates. While it is not yet clear which systems will prove commercially viable, a number of technologies do appear to be emerging as front runners. The Department of Transport highlights automatic emergency braking systems and lane departure warnings as having particularly ‘good safety potential’ (Framework for Road Safety, 2011) Electronic stability control (ESC) One technology which has already proved its worth is the ESC system which is now fitted as standard on approximately 75% of new cars (Thatcham, 2011). The system works to maintain the trajectory of the vehicle despite abrupt manoeuvres, such as the driver taking a bend too quickly. Variants of ESC are sold under several brand names, including:
Cars equipped with ESC are 25% less likely to be involved in a fatal accident (Department of Transport, 2008) and the European Commission has made ESC a mandatory fitment on all new passenger cars and commercial vehicle models registered in the EU from November 2011. From November 2014 this ruling will apply to all new vehicles. All 5 of Euro NCAP’s top performing cars of 2010 featured ESC as standard across the range:
Lane Departure Warning (LDW) Already available on the Peugeot 3008, Citroën C6 and BMW 5 Series, LDW warns the driver of a lane departure when the vehicle is travelling above a certain speed and the vehicle’s turn signal is not activated. Unlike the ESC which takes control of the vehicle away from the driver, LDW allows them to retain full control. Peugeot’s LDW system utilises six infrared sensors. Installed behind the bumper and directed towards the ground, they monitor the road and detect crossing of the white line. Two vibrators incorporated in the driver’s seat cushion warn the driver if they have crossed the white line. The vibrations are transmitted on either the left hand or right hand to indicate the side on which the lane departure has occurred. In some models the driver is warned by a sound, a vibrating steering wheel or a message will flash on the dashboard monitor. Lane Departure Warning Systems and Automatic Emergency Braking Systems will become mandatory for all new vehicles above 3.5 tons sold from November 2015. Automatic Emergency Braking (AEB)
According to Bosch, approximately 80% of drivers either do not hit the brakes at all or do not use the car’s full braking capacity before a rear-end collision. AEB systems (aka Collision Mitigation Braking System (CMBS)) take corrective action to prevent rear-end collisions if it senses that the driver has failed to respond to a potentially dangerous situation. AEB relies on a sensor mounted at the front of the vehicle to monitor the road ahead. Sensor technology varies from one manufacturer to the next but in general they can be radar, LIDAR (light detection and ranging) or camera based. If the sensor identifies a potential danger on the road ahead to which the driver has not responded, the system issues a warning (audio, visual or haptic). If the driver fails to react after the warning, the ECU will take corrective action to prevent a collision.
The new Audi A8 already benefits from AEB technology, marketed as ‘pre-sense’. The system uses two long-range radar sensors which are housed in the front bumper and can detect objects within a beam width of approximately 40°, at a distance of up to 250 metres. The radar signals deliver precise data as to the position and speed of the people, vehicles or traffic signs detected. Active Bonnet Another safety system that has recently won approval from Euro NCAP is the ‘Active Bonnet’, which improves pedestrian safety by raising the bonnet in the event of a collision. Increasing the distance between the bonnet and the top of the engine softens the pedestrian’s degree of impact and injury.
Citroën’s pyrotechnic bonnet is activated when the light beam running through a fibre optic strip (located on the front bar) is disturbed; an acceleration sensor measures the amount of deceleration at the point of impact. Measurements from both sensors are relayed to an ECU which controls the pyrotechnic actuators. Once the ECU instructs deployment, the bonnet is raised by around 65mm. Mercedes relies on three impact sensors in the front section of the car combined with pre-tensioned bonnet hinges. Upon impact with a pedestrian, the sensors send information to the ECU which, in turn, activates two solenoids in the hinges. These solenoids release the springs so that the rear section of the bonnet is pushed upwards by 50mm. Unlike the pyrotechnic systems, the electromechanical system can be easily reset by the driver in the event of false activation. The pyrotechnic system, on the other hand, can require costly repair work following a false activation as the pyrotechnic parts, catches, hinges and activators need to be replaced and the fault code reset. Global sales of automotive sensors have been increasing steadily for a number of years and estimates suggest that this trend will continue as larger numbers of vehicles demand more sensor-rich systems. As technology develops, sensors will become smaller, more numerous and continue to gain in significance for the motorist and the aftermarket. |
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Components include four wheel-speed sensors (aka ABS sensors); a steering angle sensor; a yaw-rate sensor (registers the movements of the vehicle around its vertical axis); and a lateral acceleration sensor (measures changes in acceleration). Data from the sensors is fed into an electronic control unit (ECU) which takes corrective action when necessary. For example, the system will reduce engine torque if it senses that the driver has accelerated too much going into a sharp bend.
Several manufacturers have released versions of the system in their UK models, including BMW 5-Series, Citroën C6, Honda Legend, Jaguar XF, Mercedes E-Class, and Peugeot RCZ. While Mercedes favours an electro-mechanical system, the others have developed pyrotechnic systems.