Physics behind car crash PDF

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1 Abstract This report looks into the physics and effects behind car crashes. Current developments related to vehicle safety, the effect of weather conditions on a vehicle, and a comparison of safety features will be discussed. Current Development of Vehicle Safety Automotive companies are making great progress in ensuring the safety of passengers through many technological advances. Along with systems to avoid getting in a crash altogether, many vehicles also have devices to help decrease the damage and harm to drivers during an accident. However, concerning current developments, there is still a lot of room for improvements and more innovative technology that will further decrease the risk and deaths in car accidents. Focusing on avoiding car crashes is the first step to decreasing the risk of driving. Hence, most vehicles these days are equipped with multiple devices that help keep the driver alert and safe on the road. For example, a standard feature in recent cars is a lane departure warning system in which the driver is alerted of an unintentional drift out of their lane either through the seat or steering wheel starting to vibrate. This system uses a camera to monitor lane markings on the road and thus detect when the vehicle is passing over. Depending on the advancement of the system, the vehicle can readjust the position of the car if the driver does not respond soon enough. Some more advanced features present in many high-end luxury cars such as BMW’s 7 series, Audi’s A8, and Mercedes-Benz’s S-Class is a night-vision display as seen in Fig. 1. This system uses advanced cameras to capture images and display them on the dashboard’s screen, identifying objects ahead on the road that would otherwise not have been seen even with headlights on. This device helps the driver detect and avoid any pedestrians or animals present on the road at night, thus decreasing car accidents.(1)  Another system that several automakers have developed to make sure drivers are focused is to detect the driver’s behaviour and notify them of any

2 changes. This system requires the monitors to use cameras and facial recognition software to detect tired eyes or muscles and thus pick up on erratic or unusual behaviour when driving. Another way to notice a change is, for example, how Mercedes uses a software that compares the driver’s driving style with a previous smooth operation. If the driver proves to have unusual motions, a coffee mug icon is illuminated accordingly. This system is not perfect yet as it has many flaws with being able to detect changes, but with a few updates and tweaks it will prove to be a very useful feature during a long drive. Another feature that current cars are equipped with is an around-view system of cameras that provides a full image of the car’s surroundings. The cameras are mounted in strategic places such as under the side-view mirrors, under the trunk lid, in the hood and so on. The different images are pieced together and shown on the dashboard screen, providing a bird's-eye view of the car that moves with the vehicle. Depending on the model, the driver may even be able to focus on one camera view at a time. This system is extremely useful for when the driver cannot accurately measure the parameters of the vehicle and wishes to avoid scratches or accidents with other objects. Furthermore, another feature present in some cars is an active braking system. This system uses the vehicles’ cameras to detect any hazards in the path of the car and applies the brakes accordingly to avoid a crash. In some vehicles, the system also alerts the driver to the hazard before automatically applying the brakes.(2) All of these active safety systems ensure that the driver is alert in the vehicle and that crashes are avoided as best as possible. In instances when an accident occurs despite these active features, there are still other safety systems that minimize the crash impact on the passengers. When a car crash occurs, there are many passive safety features such as airbags, seatbelts, and headrests that help minimize the impact of the vehicle. However, there is a new feature concerning airbags: external airbags. When the vehicle crashes into a pedestrian, some models from Land Rover have external airbags that save the pedestrian from severe injuries. For example, the Land Rover Discovery has a sensor tube in the front bumper that deploys an airbag in front of the windshield, softening the pedestrian’s impact as seen in Fig.2.(1) 

3 Another airbag related feature is the rear inflatable safety belt available in many vehicles such as the Ford Explorer, Ford Edge, Mercedes-Benz’s S-Class, Taurus and more. This system inflates the belts in a crash using compressed gas, increasing the surface to distribute the impact on the passenger’s body up to five times. Not only does this decrease the pressure on the passenger’s chest but also helps control head and neck motion during an accident. Having this feature greatly reduces the severity of the injuries the passengers in the vehicle experience as there is a lot of provided support. Furthermore, another feature that helps protect pedestrians that get crashed into is the deployable hood system. Available in vehicles such as the Mazda MX-5 Miata, this system raises the rear of the hood to create more room underneath for when a crash occurs, as seen in Fig. 3. This model also has impact-absorbing bumpers that help protect the pedestrian’s knees. Thus, in an accident, the pedestrian does not absorb as much shock into their knees and also has decreased head contact with the vehicle when they fall on the hood due to the energy absorbing space under it.(3)  With these passive features, the passengers in the car as well as any pedestrians or animals that get hit can avoid getting extreme injuries as there are multiple systems cushioning their impact. In addition to many current safety features, car companies are also conducting research to create more innovative technology to further increase vehicle safety. For example, many companies such as Ford are researching about two technologies that enable future cars to communicate with each other or with objects in their surroundings. The first one, Vehicle-to-Vehicle communication or V2V, works by using signals to send information back and forth between two cars about their location, speed, and direction. This information is then used to keep the vehicles a safe distance from each other. It can even help avoid many dangerous situations such as hitting a car that ran a red-light as it can sense the object before the driver can see them. Thus, the vehicle can warn the driver of the potential collision or even hit the brakes automatically. This V2V system is said to be able to reduce seventy-nine percent of vehicle

4 crashes on the road. The second system, Vehicle-to-Infrastructure communication or V2I, allows cars to communicate with road signs and traffic signals, providing information about safety issues. V2I could also request traffic information from a management system and track out the best route. With a combination of V2V and V2I, there could be a reduction of eighty-one percent of vehicle crashes. Other than these two technologies under research and development, the future of cars holds automated or “self driving” vehicles. Google has already built and tested some automated cars that use lasers, radars, and cameras to analyze and process information about their surroundings much quicker than a human. Not only could this vehicle record images of the roads but it could also find alternate routes and see things such as traffic signals much earlier than a driver.(4)  With some more research and testing, automated cars can become much more widespread and available to the general public. These vehicles that can park by themselves and navigate road traffic much better than a human have the potential to save many lives and reduce injuries as ninety-four percent of crashes are due to human error.(5)  Effects of Weather Poor weather conditions can greatly affect how a vehicle behaves on the road, increasing the chance of getting in a car accident. About sixteen percent of fatal crashes and nineteen percent of injury crashes occur during bad weather conditions. Majority of these crashes, about seventy-three percent, occur on wet pavement which happens during rainfall, snow, sleeting, or build up of ice. Only three percent of these weather-related conditions occur due to the presence of fog.(6)  The vast majority of these accidents happen on wet roads because the more rain or snow there is, the lower the friction between the tires and the pavement. On a dry road, the average coefficient of static friction between the tires and the pavement is 1.0, but this value is reduced dramatically to 0.30 when the pavement is wet.(7)  A layer of water under the tire causes the tire to lose contact with the road surface, resulting in skidding or aquaplaning. The chance of aquaplaning depends on not only the skidding resistance of the road but also on the vehicle's speed and tire tread depths. When a road has been dry for a long time, small amounts of rain can lead to immense aquaplaning as bits of oil and dust can mix with the water and produce a thin liquid layer on the road. However, if the rain gets heavier, the chance of aquaplaning actually reduces as the road surface gets swept clean.(8)  To remain safe either way, the vehicle speed

5 should be reduced by about 10-30 percent from the suggested speed limit on roads with poor driving conditions. Along with driving conditions changing during poor weather, the flow of traffic is also disrupted. Some roads or lanes may become inaccessible if they are submerged in water, snow, or have wind-blown branches and other debris on them. High winds can also knock out power from traffic signals or cause other disturbances.(6)  With a disrupted traffic flow, accidents are prone to occur as drivers become unorganized in their communication with other vehicles and irritable. It is important for car accident investigators to take into account these weather conditions in the case of a car crash due the difference in how the car behaves. If the car veered off the road and the pavement is wet, it is probably due to the low friction between the tires that resulted in the car to skid. If a large truck tipped during a turn on the road and it was known that there were extremely high winds during that time, it is most likely due to the force the wind created on the truck’s cart. There are many other examples of how the weather can affect the vehicle’s operation, making it crucial for investigators to understand these changes to figure out how the car accident occurred. Thus, important issues concerning weather conditions can be found and appropriate solutions discovered to decrease the chance of similar accidents happening. Comparing Safety Features 2018 Mercedes-AMG GT S Sports Car Table. 1. List of safety features in two vehicles.(9) (10)

Vehicle Type

2013 Honda Accord

2018 Mercedes-AMG GT S Sports Car

Retail Price

$21,680

$132,400

Safety Features

● 2 Front impact, 2 side impact, and overhead airbags ● Anti-lock brakes: senses when a tire stops rotating due to heavy braking and adjusts

● 8 air bags: 2 knee and 4 side-impact ● Collision Prevention Assist Plus: Radar-based technology alerts you if you are approaching another

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pressure to allow rotation. Increases ability to turn while braking. Stability Control: senses when handling limits are exceeded and reduces engine power or applies brakes to prevent losing control of the vehicle. Pretensioners: automatically tightens seat belt to place passenger in optimal position during a collision. Lane Departure Warning: Alerts driver when drifting out of the lane Front-crash Prevention: Uses radar technology to sense speed and distance from an object and alert driver to a potential crash.

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vehicle or object at a distance and speed that will result in a collision. The Adaptive Brake Assist automatically sets the ideal level of braking to reduce the collision. Attention Assist: Continuously monitors driving behaviour and automatically alerts driver with visual/audible warnings if drowsiness is detected. LED High-Performance Headlights: Fast responding lamps that brighten curved roads as you steer, reducing risk of crash at turns Blind Spot Assist: Radar technology senses when a vehicle has entered the blind spot area, illuminating an icon in the appropriate side mirror. An audible warning is given if the turn signal is activated while the icon is on. Rearview Camera: In reverse, a wide angle camera near the license plate displays a view on the dashboard screen of the surroundings behind the vehicle. Anti-Lock Brakes Lane Departure Warning

As seen in the chart, the more expensive and high-end vehicle has more safety features that are also much more high-tech than the average car a family owns. It definitely provides more information to the driver and makes it less likely to get in a crash or get serious injuries. Conclusion There are many factors playing into vehicle safety such as the weather conditions during a drive and the available safety features in the specific vehicle. The actual build of the car also contributes to how the vehicle functions. For example, the engine should be as close to the centre of the car as possible as it is the centre of the mass. If the centre of the mass was near the front or the back, the tires would have less of a hold on the road’s surface and they would slip. This is because the car would only have to overcome friction from two tires, not four. With a lower

7 maximum of static friction to contribute to centripetal acceleration, the car will have a tendency to slip on turns when travelling at certain speeds, making it a very dangerous vehicle.(11)  Along with taking in considerations such as the build of the automobile, there are also many other technology systems that ensure the vehicle has a good grip on the pavement, decreasing the likelihood of a crash due to sliding. These systems depend on the principles of physics laws, such as coefficients of friction, and how the car is affected by each factor.

8 Bibliography 1. Brown, A. (2016, April 05). The 5 most innovative car safety technologies. Retrieved October 20, 2017, from http://www.businessinsider.com/innovative-car-safety-technology-2016-4/#cadillacs-rear -camera-mirror-improves-rear-visibility-5 2. Jablansky, J. (2013, August 05). 7 car safety features you never you knew you needed. Retrieved October 20, 2017, from http://www.nydailynews.com/autos/7-car-safety-features-knew-needed-article-1.1417688 3. Dunn, B. (n.d.). 6 Cars With Passive Safety Systems that Stand Apart. Retrieved October 20, 2017, from https://www.autobytel.com/car-buying-guides/features/6-cars-with-passive-safety-system s-that-stand-apart-130826/ 4. Neiger, C. (2011, December 23). 5 Future Car Technologies That Truly Have a Chance. Retrieved October 21, 2017, from https://auto.howstuffworks.com/under-the-hood/trends-innovations/5-future-car-technolo gies1.htm 5. Automated Vehicles for Safety. (2017, October 18). Retrieved October 21, 2017, from https://www.nhtsa.gov/technology-innovation/automated-vehicles-safety 6. Tario, M. (2016, February). How Do Poor Weather Conditions Impact Car Accidents?. Retrieved October 22, 2017, from https://blogs.lawyers.com/attorney/personal-injury/how-do-poor-weather-conditions-imp act-car-accidents-35574/ 7. Elert, G. (2006). Coefficients of Friction for Concrete. Retrieved October 21, 2017, from https://hypertextbook.com/facts/2006/MatthewMichaels.shtml 8. Weather - In which ways does weather affect road safety? (n.d.). Retrieved October 21, 2017, from https://www.swov.nl/en/facts-figures/fact/weather-which-ways-does-weather-affect-roadsafety

9 9. 2018 Mercedes-AMG GT S | Mercedes-Benz. (n.d.). Retrieved October 23, 2017, from https://www.mbusa.com/mercedes/vehicles/model/class-GT/model-GTCA 10. 2013 Honda Accord Safety Features. (n.d.). Retrieved October 22, 2017, from https://www.autoblog.com/buy/2013-Honda-Accord/safety-features/ 11. Sill, M. (n.d.). Physics and the Automotive Industry. Retrieved October 22, 2017, from http://ffden-2.phys.uaf.edu/211.web.stuff/sill/...