Safety Features In Cars example essay topic

Describe the physics involved in the safety features in cars. Introduction Every minute, on average, at least two people die in a crash. If you read this essay from start to finish, 20 or more deaths will have occurred across the globe by the time you are done. Road traffic injuries represent about 25% of worldwide injury-related deaths (the leading cause) with an estimated 1.2 million deaths (2004) each year as said by the World Health Organization.

Car crashes will also injure at least 10 million people this year, two or three million of them seriously. All told, the hospital bills, damaged property, and other costs will add up to 1-3 percent of the world's gross domestic product, according to the Paris-based Organization for Economic Cooperation and Development. For the United States alone, the tally will amount to roughly US $200 billion. This essay will discuss how engineers have been chipping away at these staggering numbers over the past 50 years.

History Car safety has been an issue since the automobile was first invented, and was highlighted when Nicolas-Joseph Cug not crashed his steam-powered "Far dier" against a wall in 1771. One of the earliest recorded automobile fatalities was Mary Ward, on August 31, 1869 in Parsons town, Ireland. In the 1940's there was much work being done with safety in airplanes. A lot of this work focused on the take off and landing process, as this was were most plane crashes occurred.

This resulted in many improvements with the overall workings of the planes, such as brakes and engines, but also resulted in many safety features being created for the inside of the plane and its passengers. This research was the first of its kind, and many of its results started to flow over into the car-making field, and before long, safety features in cars became an industry of its own. Today there are many new products being developed every day, from night vision technology being built into windscreens, to collision avoidance systems with advanced microprocessors, radars, high-speed ICs, and signal-processing chips that take control of the car if it senses an imminent crash. There are two different types of safety features being produced today, and they can be classified into passive and active safety features.

Passive safety features try to limit the damage that a car, and therefore its passenger, will sustain during a crash, and active safety features try to stop the car from being involved in a crash at all. Active safety features are seeing the fastest growth in development, and hold the key to the future in car safety. Passive Safety Features Passive safety features in cars are very important, and are the safety features that are most known and developed. Passive safety features were the first type of safety features to be developed, starting from the 1950's and growing to a slow halt in the 1990's. A lot of the development work was done using crash test dummies, testing the damage that is obtained to the passengers in the car during a crash.

This information was then processed and used to see which parts of the body were most vulnerable and at most risk of sustaining an injury. Some of the safety features that have come about as a result of these tests are Seat Belts, Air Bags and Crumple Zones. Some other important safety features are roll cages and other structural support systems, fuel pump shut off devices and collapsible steering columns. A Seat Belt, or sometimes known as a 'Safety Belt', is a harness that is designed to secure the occupant of a car in the event of a crash. The belt will stop the occupant suffering injuries from the extreme forces that would be caused by sudden braking or a collision. Seat Belts are designed to reduce injuries by stopping passengers from being thrown into hard objects contained within the car, such as the dash or steering wheel, or at higher speeds, to save the passenger from being thrown from the car completely.

There are many different types of seatbelts, some more safe and reliable than others. The first type of seatbelt that was found in cars on a large scale was the Lap Belt. A Lap Belt is an adjustable strap that goes over a person's waist. They are found in older cars, the middle back seat in some cars and in passenger aircraft.

The Lap Belt was found to be ineffective because at high speeds passengers would suffer from spinal injuries, such as separation of the lumbar vertebrae, because of the belt. The most common seat belt that is found today is the Three-point Belt, shown on the left. The diagram shows that the belt is a single belt that goes over the passenger's chest and waist, and has three points of contact with the car. The three-point belt is very effective because it spreads the force of the crash over the shoulder, chest, waist and pelvis evenly. Most seat belts are equipped with locking mechanisms that tighten the belt when pulled hard, by the force of a passenger's body during a crash for example, but do not tighten when pulled slowly. This is implemented with a centrifugal clutch, which engages as the reel spins quickly.

Alternatively, they may also be secured by a weighted pendulum or ball bearing which when deflected by deceleration or a rollover lock on to the reel. An Airbag, also known as a Supplementary Restraint System (SRS), an Air Cushion Restraint System (ACRS), or the Supplemental Inflatable Restraint (SIR), is a flexible membrane that inflates in the event of a crash. The Airbag is used in the same way a seat belt is used, in that it is designed to protect the occupant of the car from hard or sharp objects inside of the car, such as the steering wheel or dash of the car. There are many different types of air bags designs, all created to cushions different parts of the body during a crash. Front airbags, shown on right, inflate in a medium speed head on collision to cushion the impact of the upper body on the dash of the car. Side airbags inflate in a side collision to cushion the torso.

Curtain airbags inflate to protect the head and upper body of passengers and Knee airbags inflate in frontal impact collisions to protect the driver's knees. The design idea is relatively simple. Accelerometers trigger the ignition of a gas generator propellant to very rapidly inflate a nylon fabric bag, which reduces the deceleration experienced by the passenger as they come to a stop in the crash situation. The bag has small vent holes to allow the propellant gas to be expelled relatively slowly (an airbag inflates and deflates within about 0.8 seconds) from the bag as the occupant pushes against it. The accelerometer moves in response to rapid deceleration, and this motion is detected by the electronics in the airbag system, which then sends a signal to inflate the airbag. Another very important technological improvement in passive safety features of cars is the development of Crumple Zones.

Crumple zones are specific areas within the structure of a car that are designed to break or buckle when subject to the extreme forces found during a crash. Crumple zones are created by integrating variable grades of steel and fibreglass into the front and rear-end assemblies of cars. These areas then become less rigid and more likely to give way during a crash. Sometimes crumple zones can be built into the frame of the car itself, creating areas that are more likely to bend and buckle during a crash. When the crumple zones cave in, they slow the rate that the car stops at.

This can be demonstrated by thinking of a steel block and a can of coke both hitting a wall with equal force. As the block collides with the wall, it exerts a force on the wall, after which the wall exerts an equal and opposite force on the block. At the moment of impact, the steel block stays rigid and stops almost instantly, and therefore experiences a large force. As the can collides with the wall, it does not stop as quickly. Instead, it crumples and bends, absorbing much of the energy of the collision, and slowing relatively slower, resulting in a smaller force experienced by the can. This is called controlled deceleration, and is the reason Crumple zones are so effective.

This means that as the deceleration of a car decreases, the force experienced by the car decreases. This is shown in Newtons Second Law, F = M A. this law states that if A decreases, then F must also decrease. As this result increases exponentially when large forces are in used, even a small decrease in deceleration results in a large decrease in force. All of these passive safety features have been very effective in recent yeas in decreasing the amount of deaths that occur on the road each year. They have also stopped many people suffering from serious injuries that would have left them likely to be paralysed for life.

Active Safety Features Active Safety Features are not as developed as passive safety features, but are still very important in their own right. Active Safety Features are not found in the same large numbers of cars that passive safety features are, and most active features are only found in upper class cars and are usually added features for extra cost. This is because they have not been around for as long as passive features and are much more expensive to manufacture and much more complicated to use. Despite this, they are the future of safety features in cars, and much of the technology being implemented in them are leading scientists to making cars that take control away from the driver and become completely independent machines.

Some important Active Safety Features include Autonomous cruise control system, the AWAKE System, which combines many different systems, and Electronic Stability Control Systems. Other important features are Traction Control Systems, Power Steering, Four Wheel Drive Systems, Cruise Control Systems and things such as directional Headlights and Indicators. Many modern high class cars have been fitted with a devices called Autonomous Cruise Control (ACC) Systems. In May 1998, Toyota became the first to introduce an ACC system on a production vehicle when it unveiled a laser-based system for its Progress compact luxury sedan, which it sold in Japan.

Then Nissan followed suit with a radar-based system, in the company's Cima 41 LV-2, a luxury sedan also sold only in Japan. In September 1999, Jaguar began offering an ACC for its XR coupes and convertibles sold in Germany and Britain. (ACC) systems, which add $1500 to $3000 to the cost of a car, use laser beams or radar to measure the distance from the vehicle they are in to the car ahead and its speed relative to theirs as shown on the diagram to the left. In this diagram, the red car will automatically follow the blue car, changing its speed in relation to the speed of the car in front. If a car crosses into the lane ahead, say, and the distance is now less than the preset minimum (typically a 1- or 2-second interval of separation), the system applies the brakes, slowing the car with a maximum deceleration of 3.5 m /'s 2 until it is following at the desired distance. If the leading car speeds up or moves out of the lane, the system opens the throttle until the trailing car has returned to the cruise control speed set by the driver.

Laser-based systems are significantly lower in cost than radar-based systems; however, laser-based ACC systems do not detect and track vehicles well in non-ideal weather conditions nor do they track extremely dirty (non-reflective) vehicles very well. These limitations mean that it is not very reliable and therefore a liability. Over the last few years, a major focus of traffic research has been driver fatigue as one of the most important causes of road accidents. 10-20% of all accidents are related to hypo-vigilant driver states. Furthermore, accidents related to driver hypo-vigilance are more serious than other types of accidents, since sleepy drivers often do not take evasive action prior to a collision. The AWAKE System is a combination of devices that detect drowsiness, driver awareness and the traffic situation and the involved risks to try to minimise these types of crashes.

The AWAKE Systems integrates a Hypo-vigilance Diagnosis Module (HDM) and a Traffic Risk Estimation module (TRE) then uses a Hierarchical Manager (HM) to co-ordinate the other system components. If it seems like the driver is losing concentration or is suffering from fatigue, it will use the Driver Warning System (DWS) to raise a driver's alertness. The HDM works by monitoring driver behaviour, such as eyelid behaviour and steering grip forces, and driver performance, such as their ability to stay within their lane. The TRE system works by matching data from an enhanced digital navigational map, a positioning system, an anti-collision radar, the odometer, and a driver's gaze direction sensor. The output of these modules will be used by the HM to assess the state of the driver, and to determine the adequate level of warning. The DWS uses a range of acoustic warnings including different warning tones to raise driver's alertness and speech messages to indicate why the warning has been activated.

All of these systems should combine to result in very few crashes that result from the driver becoming fatigued. Electronic Stability Control Systems are a set of device that are designed to improve a cars handling, especially when it senses that the driver might be losing control of the car. Robert Bosch GmbH and Mercedes Benz co-developed the first ESC system called Elektronische's Stability " ats programm that was used by Mercedes-Benz in their flagship S-Class. Mercedes Benz licensed this for use to other car manufacturers at no cost, including BMW with their 7 Series in 1995. ESC combines anti-lock brakes, traction control and yaw control technology. ESC sensors monitor everything from steering-wheel position and tire speed to the centrifugal forces a car undergoes while cornering.

If the sensors detect that a driver is about to lose control, microprocessors automatically apply individual brakes and reduces engine power. ESC brakes individual front or rear wheels needed to help correct under steer or oversteer. ESC also integrates all-speed traction control, which senses drive-wheel slip under acceleration and individually brakes the slipping wheel or wheels, and reduces excess engine power, until control is regained. The diagram on the left shows two identical cars, except that one is fitted with an ESC System and one is not. The red car hits a slippery section of the road and starts to oversteer, swerving off the road.

The blue car however, auto corrects using the ESC and continues along the road, with minimal oversteer at all. It is important to note, though, that ESC systems cannot re-write the laws of physics. If a car is travelling to fast when it goes round a corner, it will still lose control, no matter what control systems it has on board. Future Features Ideas such as self-driven cars are not as far off as many people would believe. Two major car companies, namely General Motors and VolksWagen have both made prototype cars that are self-driven. The car, manufactured by VolksWagen, is called the VW Golf GTi '53 plus 1' named after the number '53' that Herbie carried when racing in his movies.

The GTi uses radar and laser sensors in the grille to 'read' the road and send the details back to its computer. A sat-nav system tracks its exact position with pinpoint precision. The car can work out the twists and turns it has to negotiate and set off at break-neck speed through a laid out course on a test track. On a race circuit, it drove itself faster and more precisely than the VW engineers could manage and can accelerate independently up to its top speed of 150 mph. This is just one example of how technology is being used to create self-driven cars. Automated highway systems (AHS) are an effort to construct special lanes on existing highways that would be equipped with magnets or other infrastructure to allow vehicles to stay in the centre of the lane, while communicating with other vehicles and a central system to avoid collision and manage traffic.

The idea is that cars remain private and independent, and just use the AHS system as a quick way to move along designated routes. AHS allows specially equipped cars to join the system using special 'acceleration lanes' and to leave through 'deceleration lanes'. When leaving the system each car verifies that its driver is ready to take control of the vehicle, and if that is not the case, the system parks the car safely in a predesignated area.