Road Safety and The Laws of Motion


           Globally, an approximate of 1.3 million people die in road crashes each year, on average three thousand, two hundred and eight-seven deaths a day, according to the Association for Safe International Road Travel. Road traffic accidents rank as the ninth leading cause of death and account for 2.2% of all deaths globally.  However, in the U.S. alone, each year nearly forty-three thousand people are killed and three million people are injured in the crashes. The estimated cost of these road accidents is more than $230 billion annually. The toll from the traffic crashes is an important health and economic issue in the United States. While there are many causes of vehicle crashes, research by the U.S. Department of Transportation shows that almost one-third of the death toll could be avoided if poor road conditions and road hardware were improved (”Road Safety Audits (RSA).”).

The Laws of Motion

           Newton’s first law of motion, referred to as the law of inertia, states that a body will stay in motion or continue to move at uniform speed in a straight line unless acted upon by an external force. So, a passenger of car will be moving at the same speed as the car that they are in, even though they appear to be stationary compared to the car. If the car comes to a sudden stop, the passenger will continue to move forward at the same speed the car was moving at.

           Therefore, drivers slow down before coming to a stop. However, if  the car stops suddenly, such as when it hits a another object, such as a vehicle or building, the passenger’s body has not had time to slow down and keeps moving at the same speed the car was moving at before it’s sudden stop. The passenger’s body continues to move until some external force stops it, such as the seat in front or the windscreen (”Mary’s Pad”).

            Thus, a person can lessen the injuries experienced in a motor vehicle accident and the following safety approaches are explained by Newton’s first law which are: not speeding, which will reduce how fast the passenger’s body will be moving if the passenger has to come to a sudden stop and to wear a seat belt, which provides the external force to stop the passenger’s motion and are the main reason for reduced mortality of those in vehicle accidents.       

            Newton’s second law of motion states the force that acts on a body is directly proportional to the rate at which that body is accelerating and the constant of proportionality is mass. The car that a passenger is in is accelerating, and then hits an object, for example another vehicle. According to Newton’s first law, the passenger will continue moving, and will be stopped by an external force. The passenger’s motion stops when acted upon by an external force, such as when the passenger hits the dashboard, or the windscreen. The passenger will hit that object with a force that is the product of the mass and the acceleration of the vehicle that they were in (”Newton’s Three Laws of Motion.”).

             According to the Newton’s third law of motion, the object that stopped the passenger’s motion will hit the passenger back with the same force. This is why passengers can get injuries even from a seat belt to their internal organs, because that seat belt hits them with the same force they hit it with, and that force depends on your mass and the acceleration of the vehicle.

           Newton’s third law of motion states that to every action there is an equal and opposite reaction. Basically, if an object hits another object, the object that had gotten hit will hit the other object back with the same force. In terms of a car accident, if a passenger is hurled from a vehicle and hits the windscreen, the windscreen will hit the passenger back with a force of the exact magnitude as the force the passenger hit it with.


             Airbags help reduce injuries by spreading the force over a larger area. If the body crashes directly into the steering wheel, all the force from the steering wheel will be applied to a localized area on the body that is the size of the steering wheel, and serious injuries can occur. However, when the body hits an airbag, which is larger than a steering wheel, all the force from the airbag on the body will be spread over a larger area of the body. Therefore, the force on any particular point on the body is smaller.

             Hence, less serious injuries will occur. The airbags absorb most the exerted force, which is why the passenger will not be hit with the exerted force, and therefore relates to the Newton’s third law of motion, “for every action, there is an equal and opposite reaction”, since the passenger hits the airbag with a force that is the product of the mass and the acceleration of the vehicle. The external force, which is the airbag, is to hit the passenger with the same force they hit it with, but since the airbag absorbs some of the force, it causes fewer injuries. Newton’s laws allows us to calculate the force and therefore the pressure required to move the front of the airbag forward during inflation, and how the airbag protects us by decreasing the force on the body (”Gas Laws Save Lives. “).

            However, there are implications to this application. The airbags are only installed on the front seats of the vehicle and can cause death to children below the age of fourteen. This is a social factor since if a person and his family had a car accident, and the airbag had suffocated one of the family members, that family would never be the same again and it would be because of the airbag. More injuries are caused by wearing a seatbelt and with an airbag than wearing only a seatbelt. However, in general, airbags have caused a slightly significant reduction in the number of deaths.

            The economical factor which is a barrier to airbags is that the vast majority of airbags in cars are never deployed within the lifetime of the vehicle. The cars are flattened and recycled at the end of their lifetime, and the airbags are never removed from the cars. This can be hazardous, because these airbags still contain sodium azide, which can damage the environment. Perhaps now we can remove the airbags before flattening them, but there are millions of flatten cars still with the airbags and it is extremely difficult to remove them after the vehicle is flattened (”Gas Laws Save Lives. “)

            Since airbags cannot be deployed to all the passengers of vehicle, another application can be the use of haptic technology. According to Mobiledia, AT&T Labs, a company, has created a prototype steering wheel which incorporates haptic feedback into the steering wheel itself, alerting drivers about road hazards and helping them plan their courses by sending vibrations. The haptic steering wheel encourages drivers to keep their hands in the right place. The haptic steering wheel discourages multitasking, keeping drivers’ attention focused on the task at hand. Haptic steering system is less likely to make the people in the car feel like they do not have to pay attention. The vibrations help drivers instinctively sense which way to turn to avoid a collision by stimulating a response in the brain (”How Steering with Touch Improves Road Safety.”)

            Airbags are more efficient than the haptic steering wheel, is this perhaps might not be suitable to people of all ages, such as the elderly, and the primary issues right now is to make the different hand positions and making the signals sufficiently clear. Therefore, one has to learn the different hand positions that are required in order to drive the car and one has to know the vibration’s and signals clearly. The alternative is also affected by a cultural factor, since everyone might not accept this new type of steering wheel, and it will change how cars are driven forever and therefore people might not accept this. This alternative does not seem to be effective since it is complex and since it would be easier and adds a safety advantage to the front passengers to drive with an airbag than to drive with a new, technologically-improved steering wheel.

           Therefore, the most practical application would be the implementation of Electronic Stability Control.  Electronic Stability Control helps the person to remain in control of their vehicle when they skid, swerve suddenly or when road conditions change. Electronic Stability Control reduces the risk of single vehicle crashes by stabilizing the vehicle during sudden evasive maneuvers like swerving, improving handling on gravel and unmade roads and improving traction on slippery or icy roads. It stabilizes the vehicle by selectively braking individual wheels and reducing engine torque to bring the vehicle back on course. In some current vehicles advanced systems measure wheel slip, vehicle stability and road conditions over 23 times per second, to enable early action of avoiding an incident (Road Safety: Design & Technology.”)

           Electronic Stability Control cannot control all out of control vehicles as it works on the basics of physics. Electronic Stability Control can only control the vehicle where it is possible, according to the laws and principles of physics. Factors that affect this alternative include environmental factor and economical factor.  In the U.S., and in many other places, winter affects driving. The tires have to be changed to winter tires and on the slippery roads, it is easy to swerve and lose control. In that situation, this application would be life-saving. In single car-crashes, this technology would be vital. Or, on roads that are in harsh conditions and are made of gravel, it would be difficult to drive, especially on the roads that have been affected by weather. However, this technology would improve the person’s driving.

             The other factor is the economical factor. The electronic stability control costs between $500 and $2,600 and is an option, it is not installed in all cars, and because of it costs. Since it is expensive and since a lot of people do not realize the technologies’ life-saving potential, they would disregard and would not even consider it as an option. This factor is a barrier to the technology and as a result, there might not be a significant change in the number of deaths and accidents (”Road Safety: Design & Technology.”)

            However, this technology is currently being used and is much more effective than airbags and the haptic steering technology. The electronic stability control is much more practical and effective.


            Newton’s laws of motion apply to road safety, driving and applies to life in general. These laws of motion apply everywhere and as a result of knowing these laws, we have created calculated force using mass and acceleration and created airbags and seatbelts. The effectiveness of the airbags was average, while the effectiveness of the haptic steering wheel was low. The effectiveness of the electronic stability control was high and seems to be the most logical and practical technology in improving road safety and preventing accidents.



“Road Safety Audits (RSA).” Federal Highway Administration Research and Technology.     United States Department of Transportation, 1 Jan. 2011. Web. 17 Sep. 2012.

“Road Crash Statistics.” Association for Safe International Road Travel. Association for Safe International Road Travel, n.d. Web. 20 Sept. 2012.

“Newton’s Three Laws of Motion.” Newton’s Three Laws of Motion. CSEP, n.d. Web. 29 Sept. 2012.

Casiday, Rachel. “Gas Laws Save Lives: The Chemistry Behind Airbags.” Chemistry Behind Airbags. Howard Hughes Medical Institute, Oct. 2000. Web. 29 Sept. 2012.

“Newton’s Second Law.” The Physics Classroom.ComPADRE, n.d. Web. 29 Sept. 2012

“On Newton’s Laws of Motion and the Person in a Motor Vehicle Accident.” Mary’s Pad. Word Press, 20 Mar. 2008. Web. 30 Sept. 2012.

Knibbs, Kate. “How Steering with Touch Improves Road Safety.” Mobiledia.Mobiledia Corp, 6 Aug. 2012. Web. 30 Sept. 2012.

“Road Safety: Design & Technology.” Department of Planning, Transport and Infrastructure. Department of Planning, Transport and Infrastructure, n.d. Web. 29 Sept. 2012.

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