Aug 22, 2005 02:03 PM
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(Updated Sep 20, 2005 01:29 PM)
What's the No. 1 thing that a driver is likely to do when there's a problem on the road ahead? Step on the brakes, of course.
But braking a car safely isn't as easy as it may seem. Sudden, panic stops can lead to skidding and loss of steering control.
ABS : The addition of electronics to automotive brakes in recent years spawned all manner of new brake systems with acronyms such as ABS(Anti-lock brakes) and EBD (Electronic Brakeforce Distribution). ABS uses electronics at each wheel to rigorously ''pulse'' the brakes faster than any driver physically could during panic stops. This rapid pulsing prevents the brakes from locking up the wheels during hard, sudden stops and on some slippery surfaces. Wheel lockup is a problem to be avoided because it can cause skids and prevent drivers from maintaining steering control. Note, though, that ABS only activates in sudden, hard braking when a driver maintains severe pressure on the brake pedal. It does not activate in milder, everyday stops, such as those at a stop sign. It's also important to recognize that to benefit from ABS, a driver must be comfortable using this system. This typically means a driver needs to practice making panic stops and understand what ABS provides—namely, the ability to steer around obstacles while they're in an emergency, hard braking maneuver.
Many drivers freeze behind the wheel in such circumstances. As they try to stop the car as quickly as possible, they forget to steer away from the problem. Thus, there's the need for drivers to go to a vacant parking lot, say on a Sunday morning, and practice emergency braking and steering in ABS-equipped vehicles to learn how to take advantage of ABS, ABS does not necessarily reduce the distance needed to stop the car.
Electronic Brakeforce Distribution, or EBD, follows on top of ABS. it works automatically—without driver input—to distribute braking force among the wheels to ensure the vehicle stops stably. Without EBD, there can be circumstances where a vehicle's brake force is more heavily skewed to one part of the car, resulting in the vehicle pulling to one side and unnerving the driver or even causing a skid.
Brake Assist, known as BA, is another electronic braking system and is often partnered with EBD. BA monitors a driver's braking and if it detects that a driver is in an emergency braking maneuver, it automatically supplements the driver's attempt to stop quickly by boosting brake power to the maximum. BA stops working immediately after the driver lifts up on the brake pedal. Unlike ABS, BA can help improve vehicle stopping distances. Research has shown the system even helps pro drivers stop more effectively.
https://autos.msn.com/advice/article.aspx?contentid=4023227
Supplemental Restraint Systems (SRS) Airbags
What is an airbag? : Airbags are known as Supplemental Restraint Systems (SRS) and are not a substitute for the use of seatbelts. For the particulars of your vehicle’s system you should consult your owner’s manual. If airbags are fitted, the steering wheel cover and/or dashboard cover will usually have the words ‘airbag’ or ‘SRS airbag’ moulded into them. An airbag is a fabric bag that inflates rapidly when required from the steering wheel centre or dashboard. The SRS airbag inflator contains a solid chemical gas generator. The solid chemicals are safely stored in a metal chamber inside the SRS airbag module. Each inflator is sealed to keep out moisture. SRS airbags are designed to deploy in moderate to major crashes only and should not deploy in minor crashes.
The following four steps show how the SRS airbag works: In an impact, sensors in the vehicle detect the sudden deceleration. If the crash is severe enough electricity flows to the inflator and causes ignition of the gas generator. The gas generator then rapidly burns in the metal chamber. The rapid burning produces inert gases and small amounts of dust. The inert gases and dust are cooled and filtered during inflation of the airbag.The inflating airbag splits open the trim cover. The airbag then rapidly unfolds and inflates in front of the occupant. Note: these steps take place in a fraction of a second. After inflation, the gas is vented through openings or open weave areas in the airbag. Airbags deflate in under a second and may be pushed aside for occupants to exit.
When should it work? : There is a general misconception that airbags provide a soft cushion and will prevent bruising or other minor injuries in low severity crashes - this is incorrect. SRS airbags are designed to reduce peak loads on the head and chest in severe crashes (those where death or long term brain injury are possible). When deploying, the airbag is firm, but it absorbs energy as the gases are released through the vents.
While airbags significantly reduce the risk of serious or fatal injury in crashes, there are some risks from the deployment of airbags in low speed crashes. For this reason modern cars use a range of intelligent sensing functions to ensure that a crash is really happening (not just a bump in the road or a minor knock in the car park) and to fire airbags at the best time. This reduces the likelihood of airbags deploying in minor crashes.
Modern design and construction methods used in today’s vehicles include progressive crumple zones in the body and frame structure to reduce the rate of deceleration in severe frontal impacts. For this reason, damage sustained by a vehicle in a head on collision may appear quite extensive and the airbags may not have deployed because the crumple zones have absorbed a significant amount of the energy of the impact. In these cases, the airbag sensors have detected that the rate of vehicle deceleration has not been sufficient to require triggering of the airbags.
Typically, the driver and or passenger airbags deploy in head-on collisions where the force of the impact is equal to or greater than striking an immovable and non deformable barrier (such as steel or concrete) at a speed of around 18-25 km/h or higher. In offset collisions or in a head-on collision with another vehicle or other deformable and/or movable object, the speed would generally need to be significantly higher than 25 km/h for the airbags to deploy. Airbags designed for frontal impacts usually do not deploy in rear end collisions, side impacts, rollover accidents or in most underride accidents.
https://raa.net/page.asp?TerID=299
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