The reduction of nationwide speed limits to 60 miles per hour (mph) has the potential to save some 3,000 lives per year (Shafi, Parks, Gentilello, 2008). Through the utilization of the CRASHCOST software provided by the National Highway Traffic Safety Administration and through the calculations of maximizing fuel efficiency through miles per gallon (MPG), the pros and cons of the possible national speed limit reduction can be ascertained. Given that by law one is allowed to drive up to 5 miles over the speed limit, the current analysis has been undertaken with the assumption that most drivers would be moving at a median rate of 65 mph. This variable has been utilized to measure the savings of cost through the implementation of this proposed injury prevention strategy.
A CRASHCOST software report issued in 2003 estimated total economic costs over a lifetime associated with motor vehicle collisions with speeds exceeding 65 mph. In addition, the number of collisions and subsequent costs were calculated if the speed limit of the accidents were nationally reduced to 65 mph. The collision-rate estimations after the reduction of the speed limit variable were determined through the comparison of states with current speed limits of 65 mph and those with limits higher than 65 mph. These collision rates were adjusted for the amount of miles traveled, the utilization of a safety belt, the presence of air bags, etc. Savings potential (benefit) was equated to the difference between the state limits (cost). As a result, the estimated potential savings after the speed limit restriction of 65 was found to be an annual $13 billion; $2 billion of which included a reduction in costs related to trauma care (Shafi, Parks, Gentilello, 2008). The savings are a reflection of the approximate total economic damage of 6% that motor-vehicle crashes are responsible for (an estimated $319 billion adjusted for current inflation) (Shafi, Parks, Gentilello, 2008). With safety belt usage, the National Highway Traffic Safety Administration estimated annual savings of up to $50 billion, approximately $2 billion with the presence of air bags, and $670 million if all motorcyclists wore helmets (Shafi, Parks, Gentilello, 2008). With the reduction in deaths and injuries associated with motor-vehicles, cost will also be reduced. In consequence, a significant boost in savings will be earned.
Regardless of the make of a given vehicle, its engine, or the overall size, the gas mileage of a car has been proven to decrease once past the optimal speed (MPG For Speed, n.d.). According to a study calculated by Green Car Congress, the optimal mileage for maximum fuel efficiency hovers between 55-60 mph (MPG For Speed, n.d.). Studies that are supported by the Department of Energy will ascertain that the average car will drive at maximum fuel efficiency around the previous numbers as well (MPG For Speed, n.d.). However, as the speed increases, a given car is reportedly 8% less efficient at a rate of 65 mph, more than doubling in lost efficiency at 70 mph (17%), 23% less efficient at a rate of 75 mph, and finally more than tripling in lost efficiency at 80 mph (28%) (MPG For Speed, n.d.).
The reduction in efficiency is twofold; the first being increased air resistance. In a study published by CNN, “Pushing air around actually takes up about 40% of a car’s energy at highway speeds. Traveling faster makes the job even harder…The increase is actually exponential, meaning wind resistance rises much more steeply between 70 and 80 mph than it does between 50 and 60” (Valdes-Dapena, 2008). Secondly, various engines are designed with a specific temperature, average speed, and range of revolutions per minute (RPM) in mind (MPG For Speed, n.d.). If one were to drive out of the ranges designed for the engine being used, the efficiency would obviously decrease. It has been determined that approximately 1 billion barrels of oil annually would be saved if the national speed limit were lowered between 55-60 mph (MPG For Speed, n.d.). The principle applies to all vehicles that consume fossil fuels; most especially airplanes.
- Furlong, S. R., Kraft, M. E. (2015). Public Policy: Policies, Analysis, and Alternatives. Thousand Oaks, CA: SAGE Publications.
- MPG For Speed (n.d.). Speed Kills MPG. Retrieved April 15, 2016 from http://www.mpgforspeed.com/
- Shafi, S., MD, Parks, J., MPH, & Gentilello, L., MD. (2008). Cost Benefits of Reduction in Motor Vehicle Injures With a Nationwide Speed Limit of 65 Miles Per Hour (mph). The Journal of Trauma Care and Acute Care Surgery, 65(5), 1122-1125. doi:10.1097/TA.0b013e318189a821
- Valdes-Dapena, P. (27 March 2008). Slow down a little, save a lot of gas. Retrieved April 15, 2016 from http://money.cnn.com/2008/03/26/autos/slow_down_save_gas/index.htm? cnn=yes
