Safety According to the NHTSA
By Jeff Youngs, February 24, 2012
Each year, nearly two million injury-causing car accidents take place in the United States, and more than 30,000 passenger-vehicle occupants die in those crashes. Given such sobering statistics, safety should factor into your purchase decision just as much as or more than any other feature, especially if you're buying a family vehicle. Today's cars, in general, are far safer than those of the past, but some are safer than others.
Finding Safety Data
The two main organizations that perform automotive safety testing are the National Highway Traffic Safety Administration (NHTSA) and theInsurance Institute for Highway Safety (IIHS). Both have easy-to-useWeb sites (safercar.gov and
History of the NHTSA
The NHTSA is a government agency, while the IIHS is a non profit organization supported by insurance companies. The NHTSA is part of theU.S. Department of Transportation and it conducts automotive safety testing in its New Car Assessment Program (NCAP). According to theNHTSA, the goal of the NCAP is "to improve occupant safety by providing market incentives for vehicle manufacturers to voluntarily design their vehicles to better protect occupants in a crash and be less susceptible to rollover, rather than by regulatory directives."
Under the NCAP, the NHTSA began performing frontal crashes in 1979.Side crash tests were added with the 1997 model year, and rollover ratings started with 2001-model-year vehicles. The now-familiar 5-star rating system began with 1994-model-year vehicles, and manufacturers were required to place NCAP star ratings on new-vehicle window stickers as of September 1, 2007.
The NHTSA contracts with five labs around the country to conduct its front and side crash testing, and it uses two additional labs for rollover testing.
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Each year, roughly 80 to 100 vehicles are subjected to NCAP testing.With 250 or so new vehicles on the market every year, the agency can't test them all. So, three types of new vehicles are chosen: those that are predicted to sell in high numbers, those that have been redesigned and given structural changes, and those with new safety equipment.Ratings for vehicles that haven't significantly changed are carried over year to year. All told, the agency aims to have ratings for 85percent of the new vehicles sold each year. Whether they are tested or not, all new vehicles sold in the United States are subject to Federal safety standards.
Vehicles are categorized as passenger cars, sport utility vehicles,pickup trucks and vans. Passenger cars are further broken down by curb weight into mini (1500-1999 pounds), light (2000-2499 pounds), compact(2500-2999 pounds), medium (3000-3499 pounds) and heavy (over 3500pounds).
The NCAP includes three types of tests and assigns up to six ratings on a 1- to 5-star scale based on the percentage chance of serious injury.The tests include a front impact with ratings given for driver and front passenger, a side impact with ratings for the driver and rear passenger (on the driver's side), and a rollover resistance rating for both 2-wheel drive (2WD) and 4-wheel drive (4WD) models, if appropriate. The NCAP does not include rear-impact testing.
The Web site safercar.gov has ratings for vehicles dating back to 1990.Data is available going all the way back to 1979, but anything before1990 is archived. To get data for older cars, send an e-mail email@example.com with the year,make and model of the vehicle in question.
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The frontal impact test is a 35-mph crash (5 mph faster than required by the Federal standard) with dummies representing average-sized adults buckled into the driver and front passenger seats. The vehicle is run into a stationary rigid barrier head-on, impacting the entire front of the vehicle. The NHTSA says this test is the equivalent of a head-on-crash between two identical vehicles. The results are comparable with vehicles that are about the same height and are within 250 pounds of the vehicle tested. The results are not otherwise comparable across categories, which is an important distinction to make for any consumer cross-shopping vehicle categories. For example, a top crash rating fora compact car and a top crash rating for a midsize SUV does not mean that the compact car will provide the same crash protection as the midsize SUV if the two were involved in a head-on crash. Given equivalent ratings, physics dictate that a heavier vehicle will usually be safer in a crash.
Forces to the dummies' head, neck, chest, pelvis, legs and feet a remeasured for impact forces. The star ratings assigned indicate the percentage chance that the occupants will suffer a serious injury. TheNHTSA defines a serious injury as one requiring immediate hospitalization or one that may be life-threatening. A 5-star rating in the frontal impact test indicates a 10 percent or less chance of serious injury. Four stars means an 11 to 20 percent chance. Three stars denotes a 21 to 35 percent chance. Two stars indicates a 36 to 45percent chance, and one star represents a 46 percent or greater chance of serious injury.
When customers look up NCAP crash test ratings on the NHTSA's Web site(safercar.gov), information beyond the star ratings is available. In the frontal crash test, the site also lists findings for Head InjuryCriterion, Chest Deceleration g forces, and left and right Femur Load in pounds. Force to the thigh greater than 2250 pounds is noted as a high likelihood of thigh injury. The results of all these scores are considered when the agency assigns its star ratings.
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The NCAP side-impact crash test involves a vehicle with dummies buckled into the driver's seat and driver's-side rear passenger seat (or second row in the case of three-row vehicles). Once again, the dummies represent average-sized male adults. By comparison, the IIHS test uses dummies the size of fifth-percentile females or 12-year-old children.
The vehicle undergoing the test is stationary and is struck perpendicularly in the side by a 3015-pound barrier moving at 38.5 mph(again, 5 mph faster than required by the Federal standard). The moving barrier is low like a car, not high like an SUV as in the IIHS side-impact test. The barrier also has "give" to replicate the crush zone in the front of a vehicle. Since all vehicles tested are impacted by the same size barrier, side crash test results can be compared with each other, even across categories.
Forces to each dummy's head, neck, chest and pelvis are measured. Head injury risk is not included in the current NCAP side-impact test ratings. Instead, excessive head injury is reported as a safety concern.
The side-impact crash ratings denote the chance of a life-threatening chest injury for the driver, front passenger, and outboard rear passengers. A 5-star rating in the side-impact test indicates a 5percent or less chance of serious injury. Four stars means a 6 to 10percent chance, 3 stars are assigned for an 11 to 20 percent chance, 2stars represent a 21 to 25 percent chance, and vehicles with a 1-star rating pose a 26 percent or greater chance of serious injury.
Like the frontal crash test, safercar.gov lists information beyond the star ratings for the side-impact test. In this case, the findings are for Head Injury Criterion2 (HIC), Thoracic Trauma Index (TTI), andPelvis Deceleration g forces. The average TTI value for 2003 to 2006vehicles was 55. Force to the head greater than 1000 HIC is noted as a high likelihood of head injury. Force to the pelvis greater than 130g's is noted as a high likelihood of pelvic injury.
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In 2003, just 1.8 percent of police-reported crashes resulted in a rollover, though SUVs were higher at 5.3 percent. While the percentage of these crashes is low, some 10,000 people each year die in rollover crashes, accounting for 33 percent of occupants killed. Many of those who die are unbuckled passengers thrown from their vehicles. According to the NHTSA, your chances of dying in a rollover crash are reduced by75 percent if you wear a seat belt.
The NCAP's Rollover Resistance rating measures the chance a vehicle will roll over if it is involved in a single-vehicle crash. The rating is based on two factors: an at-rest measurement known as the StaticStability Factor (SSF) and a dynamic test, which became part of the program with the 2004 model year.
The SSF determines how top-heavy a vehicle is by comparing the track width to the center of gravity. SSF scores generally fall between 1.0and 1.5. A high SSF score means a vehicle is less likely to roll over.Cars tend to land between 1.3 and 1.5, while high-riding SUVs, pickups and minivans fall in the 1.0 to 1.3 range.
For the dynamic test, the vehicle is given a full tank of gas and loaded with weight to approximate five occupants. The added weight effectively raises the vehicle's center of gravity, making it more prone to a rollover. The dynamic test involves a fishhook maneuver to represent an obstacle avoidance situation. With the vehicle traveling at 35-50 mph, the steering wheel is turned 270 degrees in one direction, then 540 degrees in the other direction, both within about one second. Instruments on the inside wheels measure if the wheels liftoff the pavement during the maneuver. If both inside tires lift at least 2 inches, the vehicle is considered to have tipped up. If a vehicle doesn't tip at 35 mph, it is run again at 40, then 45 and finally 50 mph. If it doesn't tip at all, it is listed as "No-tip."
The NHTSA says that about 95 percent of rollovers are "tripped" by the vehicle striking something low, such as a curb or ditch, or by going off the road and digging into soft soil. Top-heavy vehicles are more susceptible to rolling in this manner. The SSF rating reflects this more common type of rollover and therefore is weighted more heavily in the overall Rollover Resistance rating. The dynamic rating measures untripped rollovers and counts less in the overall rating.
The overall Rollover Resistance rating is also expressed on a 1- to5-star scale. On the safercar.gov Web site, the actual percentage chance of a rollover is listed, as is the SSF. Dynamic test result information is also shown. This result is listed as "Tip," "No-tip," or"No tip*." The asterisk means the vehicle wasn't tested but the results were ascribed based on results of vehicles with lower SSF scores that didn't tip up during the dynamic test.
A diamond and bar graphic is also displayed on the Web site. It shows three pieces of information: the star rating, the actual percentage chance of a rollover if involved in a single-vehicle crash, and the range of percentages of all vehicles in that class for the last threemodel years.
For example, Vehicle X, a midsize SUV, has a 4-star rollover rating, a1.30 SSF, a "No-tip" Dynamic Test result, and a 14 percent chance of rolling over in a single-vehicle accident. While it doesn't earn a5-star rating (no SUV does) the diamond and bar graphic shows that its14 percent chance of rollover is at or near the best in the class,while the worst in the class is about 34 percent.
Like the side-impact crash test, rollover resistance ratings can be compared among different types of vehicles because they are all subjected to the same tests.
The NHTSA says a vehicle that gets a 1-star rollover resistance rating is four times more likely to roll over in a single vehicle accident.Even 5-star vehicles have up to a 10 percent chance of rolling over in a single-vehicle crash. In fact, the NHTSA notes that some 5-star vehicles, such as sports cars, may have a higher number of rollovers per 100 registered vehicles than 3-star vehicles, such as minivans.Driver behavior plays a part here, as sports car drivers tend to be much more aggressive than minivan drivers, the NHTSA says.
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Unlike the IIHS, the NHTSA does not give awards for the best safety performers in its New Car Assessment Program. Instead, vehicles that earn 5-star ratings for the driver and front passenger in front impact tests and the driver and driver's-side rear passenger in side-impact tests are considered the top performers in NCAP testing. While there are no awards for these "Quad 5" or "5/5/5/5" vehicles, we are recognizing them here. Note that the NCAP's rollover test ratings are not included in the 5/5/5/5 ratings; our list only includes those vehicles that also earned a 4- or 5-star rollover rating. In addition to the vehicles listed below by class, the following vehicles get Quad5 ratings, but do not qualify for the list due to their 3-star rollover ratings:
EscaladeESV/ EscaladeEXT ChevroletAvalanche
FordCrown Victoria (with side air bags)
MercuryGrand Marquis (with side air bags)
NissanAltima sedan/Altima Hybrid
SaturnAura/Aura Green Line
DodgeCaliber (with side air bags)
JeepGrand Cherokee (4WD only)
Kia Sorento(4WD only)
FordExpedition (4WD only)
LincolnNavigator (4WD only)
KiaSportage (4WD only)
MitsubishiRaider (Quad Cab)
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Beyond using its safety testing as a guide, the NHTSA recommends consumers choose vehicles with electronic stability control (ESC) and side air bags that offer head protection.
Electronic Stability Control
ESC, also generically called anti-skid control, is known by many names.General Motors calls its system StabiliTrak,
No matter the name, ESC uses sensors to detect a loss of grip or vehicle instability, then works automatically with the anti-lock-braking system (ABS) to apply individual brakes to help keep the vehicle on its intended path. In some cases, ESC also reduces engine power.
So how does that affect daily driving? Hopefully, you'll use ESC rarely, if ever. However, if you approach a corner too fast and your vehicle begins to plow straight ahead, ESC detects that the vehicle is not on its intended path and tries to correct the situation by applying the inside brakes. This will rotate the vehicle through the turn and,it's hoped, save you from going off the road. Be aware that ESC can't defy the laws of physics, so it won't allow you to make a 90-degree left turn at 90 mph and it won't really help on glare ice, but it can be quite helpful in other emergency situations.
Based on a NHTSA study of U.S. crash test data, ESC reduces single-vehicle accidents in passenger cars by 26 percent and SUVs by 48percent. The agency also estimates that ESC has the potential to prevent 64 percent of passenger car rollovers and 85 percent of SUV rollovers. The study also found that ESC can prevent a certain percentage of multi-vehicle accidents involving SUVs.
Given these findings, the NHTSA has issued a Federal motor vehicle safety standard that requires ESC on passenger cars, multipurpose passenger vehicles, trucks, and buses with gross vehicle weight ratings of less than 10,000 pounds by the 2012 model year.
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While head injuries are not factored into the NCAP's side-impact crash ratings, the NHTSA says head-protecting side air bags (generally,curtain side air bags) provide a significant benefit. The NHTSA estimates that if all U.S. vehicles were equipped with these air bags,700 to 1000 lives would be saved per year in side-impact crashes. The agency also estimates that in side-impact crashes involving at least one fatality, almost 60 percent of those killed have suffered brain injuries.
These and other safety features are listed on the individual results page for every vehicle sold in the U.S., whether the NHTSA tests them or not. So, if you want to find out what safety equipment is offered on a vehicle you are considering, check out the individual results page onsafercar.gov. Other safety features listed there include air bag on/off switches, 4-wheel ABS, traction control, tire-pressure monitor(required as of the 2008 model year), auto-dimming rearview mirror,daytime running lights, automatic door locks, automatic crash notification, safety power windows, built-in child seats, Lower Anchors and Tethers for CHildren (LATCH), interior trunk release, and anti-theft features.
For more information on the NHTSA's recommended features and driving practices, check out the "Buying a Safer Car" brochure available atsafercar.gov.
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TheFuture of NCAP
The NHTSA sees several ways that it could improve the NCAP. In general,with the majority of vehicles receiving 4 or 5 stars in the front and side tests, reworked criteria for each test could provide better information about the differences among vehicles. The agency believes its frontal crash testing can be improved by evaluating and possibly adding a lower speed (25 mph or below) test, and evaluating injuries to the knees, thighs and hips.
There are several ways the NHTSA believes it could improve side crash testing. The current test uses a deformable barrier that was designed to represent the height and weight of an early 1980s passenger car.Changing the barrier to the same barrier used by the IIHS, which represents a truck or SUV, is a possibility, as are changing the barrier's impact angle and impact location. Another test could be incorporated using a narrow object to represent a pole in addition to the full-width barrier. Head-injury readings would be taken in this test, and two types of dummies could be used. Any vehicle would need head-protecting side air bags to perform well in this test, thus encouraging expanded installation of this valuable safety technology.Other proposals include using new dummies that can be used to measure additional lateral injuries, increasing the speed of the impact in the test, and developing test procedures that better evaluate injury risk in vehicles fully equipped with both torso-protecting front side and head-protecting curtain air bags.
While ESC is not considered in the NCAP rollover test, it has the potential to reduce passenger car rollover crashes by 64 percent andSUV rollovers by 85 percent, as mentioned above. The NHTSA says most of the benefit of ESC in rollover reduction is not due to ESC decreasing rollover risk. Instead, it is due to ESC's ability to reduce loss of control that can lead to vehicles leaving the road, which greatly increases the chance of a rollover. The NHTSA feels that a new rollover risk model may result by comparing crash statistics for vehicles equipped with ESC versus those without.
Unlike the IIHS, the NHTSA does not perform rear crash tests. The agency is considering linking to IIHS rear crash test results,providing real-world rear crash safety data by vehicle class, and eventually conducting its own dynamic test.
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Crash avoidance is another theme the NHTSA wants to promote.Specifically, the NHTSA pinpoints three crash avoidance technologies that it sees as priorities: ESC, Lane Departure Avoidance/Warning, andRear-end Collision Avoidance. Lane-departure warning systems track vehicle position in a lane and warn the driver or even help the driver steer back into the lane if they detect the vehicle has crossed lane lines without the use of a turn signal. Rear-end collision avoidance systems detect vehicles ahead, usually through radar, and warn the driver when a crash seems imminent and, in some cases, apply the brakes to prevent rear-end collisions.
To entice customers to choose these technologies, the NHTSA is considering adding a Crash Avoidance Rating, probably given as a letter grade of A, B or C. Two possibilities are on the table. In the first,each technology would be weighted equally and a vehicle offering all three would get an A, two a B, and one a C. The other option is to evaluate each technology's effectiveness and weight the letter grades.In this case, ESC, which is the most effective of the three, might automatically earn a B grade by itself. In the future, crash avoidance tests may be added and a star rating system could be developed.
Other technologies exist that reduce harm before, during and after a crash. Examples include imminent crash braking, automatic seat position adjustment, automatic head restraint adjustment, and advanced adaptive restraints. The NHTSA plans to monitor these technologies, determine their potential safety benefits, and evaluate if incorporating them into NCAP would accelerate their deployment in the market.
Finally, the NHTSA intends to enhance the presentation of the NCAP ratings. The first step is to implement a summary crash rating and eventually transition to one overall rating that will incorporate crash worthiness and crash avoidance star ratings. This rating would incorporate front, side and rollover ratings with recommended safety technologies. The information may be presented on a 1 to 100 scale.
Whether the NHTSA makes all these changes or not, its NCAP ratings are valuable information for car buyers, and they should be weighed carefully when making a new-vehicle purchase.
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