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· Autonomous cars have the potential to improve overall safety by taking away and minimize the human factor.
· As seen in the front Collision avoidance, no of accidents have been reduced, thus in the same manner some rear end collision avoidance system could be introduced, where the car warns the drive to accelerate to avoid collision.
· Maintain the distance from the lead vehicle (avoid tailgating).
How to avoid rear end crashes
The NTSB estimates that nearly 80% of the deaths and injuries resulting from rear-end collisions could be prevented by Use of collision avoidance systems and with Latest Development in technology like Autonomous car, connected vehicular technology which can be implemented in all cars to avoid the crashes happing today.
The first thing which needs to be thought is to reduce the Impact force pushing the occupant forward and second to early head and headrest contact. Some of the System developed based on above two things are active headrest from SAAB. WHIPS introduced by Volvo a Recliner in the seats for more yielding. (13)
Figure 2 – Direction of Force acting (12)
In order to prevent whiplash injuries new systems have been introduced. These are mainly systems belonging in the integrated safety, meaning that the systems are deployed just before the crash happens. Studies indicated that the head restraint position relativity to the neck position is of major importance. (9) Therefore, most new systems try to minimize the relative position between the head and the restraint. That is done by utilizing belt pre-tensioners and active head restraints. Other researchers tried to utilize the whole seat instead. An example of this is the Adaptive seat (ADSEAT), which proved to provide some significant reduction in the NIC and Nkm criteria. (11)
Especially for the whiplash injuries, a new dummy model has been developed called Bio-fidelic Rear Impact Dummy (BioRID). (10) This dummy proved very helpful in the understanding of the whiplash injuries. A new neck injury criteria (NIC) is also being utilized successfully thanks to that study.
Rear-end crashes may be of the most common ones, though they account for only a small percentage of fatalities. However, they are known to provoke types of injuries like neck (whiplash) and back related injuries, that are proven to be damaging in the long term. Spinal disc injury is an injury found to be concerning, it is caused because of violent forces driving the passenger backward which causes spine to bulge and damages the nerves and pelvic region. Whiplash injury is caused due to rapid acceleration of head relative to the torso, often due to low speed rear impact. There are other long-term effects seen on the body due to mainly nerve damage that appear only after some time. (8) Insurance companies have found that 66% of insurance claims for bodily injuries in 1992 included neck sprains. (9) Newer studies from the European Union indicate that even more people suffer from whiplash injuries and that results in a substantial money cost (Euro NCAP 2013).
According to studies though it is not safe to generalize as depending on the area of the world different factors can be the most contributing ones. For instance, in China it has been found that most rear-end crashes have not been because of inattention and driver related visual scanning in high traffic, which were the main factors in the US. That happens since drivers in China adopt a more aggressive driving style to get more space for themselves, therefore they are used to the traffic situation and they do not get easily distracted. The low safety margins the Chinese drivers adopt however, especially tailgating as in Abu Dhabi (6), was found to be the main reason behind rear-end crashes in China. (7)
Significant research effort has been undertaken to analyze the characteristics and causes of the rear-end crashes in different parts of the world. Researchers have tested many different scenarios, while the effect of several variables has been investigated. Most researchers working with crash data assumed a statistical model and tried to understand the main factors behind rear-end crashes. Among the top causation factors has been found to be: driving experience, speeding, tailgating for the driver’s behavior and as expected environment conditions such as road, weather and light conditions play a major role too as in the most crashes. (6)
REVIEW – State of Art
Injuries, Countermeasures, Protective system and use of Active Safety New advancement will be discussed in the subsequent sections
Active safety systems nowadays are being used to help with the mitigation of crash severity. Various systems have been investigated like for example active head restraints, the Whiplash Protection System (WHIPS), belt pre-tensioners, forward collision avoidance technology, driver assist etc.
Spinal related injuries and neck injuries (whiplash) have been found to be the most common type of injury in these kinds of crashes. Most of the time their effect appears in the long term, something that is troublesome for the patient.
As the study from 100 car naturalistic data shows most rear end crashes happen at very low speed (approx. mean speed 15mph) (5). Therefore, this report tries to focus on Scenario of two vehicles of same type with low speed impact and injuries sustained during this.
Studies done by NHTSA (5) has found that about 90% of the rear end Crash is caused by driver distraction. There has been also Initiatives from Governments by bringing a regulatory change for example implementation of high mounted stop lamp resulting in reduction of 4% of rear collision (5) and rear end impact testing to make the vehicle safe. Also with continuous research by OEM’s to make vehicle safe like enhanced rear lighting and signaling systems, seat belts, seat recliner, active headrest etc. play an important role in protecting the occupants.
Rear end collision in which the lead car is either slowing down or stationary and impact happens from the behind by another car which is following lead car. There are lot of Variables which are involved in this type of collision like size of the vehicle, speed of the vehicle, Involved Occupants – Male or Female etc. which determines the severity of the crash. Naturalistic data (100 Car study) showed that drivers using cellphones are twice as likely as other drivers to cause rear end collisions (4).
Figure 1- Rear End Crash Stats (3)
More than 1.25 million people die each year as result of road traffic crashes. 20 – 30 million people suffer non-fatal injuries. Speeding, distraction, unsafe road infrastructure, unsafe vehicles are some of the reasons for road accidents (1). Rear-end impacts are considered of the most frequent types of crashes over the world, particularly in US and lead to a significant number of injuries and fatalities. They occur very sudden and the injuries are most evident at the time of accident but may cause in later stages. About 28% of crashes are rear end collisions. Out of which 23% of crashes occur due to run-off or loss of control and 9% are caused by bad lane changes (2). There is a lot of research going on to understand the reasons for the occurrence and the severity of rear-end impacts.