How to Select the Safest Car

A crash course in crash tests and new vehicle technologies to help you find the right car for you.

The National Highway Traffic Safety Administration (NHTSA) reported that there were 5,687,000 vehicle crashes in the United States in 2013 with 1,591,000 (28 percent) resulting in injury and 30,057 (0.5 percent) resulting in one or more fatalities. That is more than one accident every 5 seconds. With these staggering facts, one of the most common questions AAA receives from members is “what is the safest car?” While there is no simple answer, AAA can help identify resources you can use to understand vehicle crash ratings and provide information on the latest technology that are making cars safer than ever.


Above: A Nissan Murano undergoing the Insurance Institute for Highway Safety's small overlap frontal test, during which 25 percent of the vehicle on the driver's side hits a rigid barrier with the car traveling at 40 mph. Insurance Institute for Highway Safety photo

Below: The dummy's position in relation to the door frame, steering wheel, and instrument panel after this crash test indicate the driver's survival space was maintained well. Insurance Institute for Highway Safety photo



The National Highway Traffic Safety Administration is the agency of the U.S. Department of Transportation that conducts safety tests to determine how well new vehicles protect drivers and passengers during a crash, how well vehicles resist rollovers, and whether vehicles are equipped with technology that can help avoid crashes. Each year, NHTSA tests new passenger cars, pickup trucks, sport utility vehicles (SUVs) and vans, focusing on new models as well as those that have undergone major design changes or include new advanced safety features.

These vehicles are then rated using the 5-Star Safety Ratings system. Five stars indicate the highest safety rating and one star the lowest. It is worth noting that even a 1-star rating indicates that the vehicle passed the minimum safety regulations to be sold in the United States. Although it is impossible to determine how well vehicles protect drivers and passengers in all types of crashes, star ratings are a useful way to compare the relative safety of different vehicles.

NHTSA performs four separate tests that use instrumented crash test dummies simulating different size drivers and passengers. The impact forces on the various parts of the dummies are measured and compared with the forces needed to cause injury. The results are combined for a single overall crash survivability score, also 1 to 5 stars. The weight of the vehicle has a large effect on crash survivability, with the heaviest vehicles displaying the lowest occupant risk. Shower, extremely heavy vehicles tend to be harder to maneuver, often providing inferior crash avoidance. The four tests include:

  • Frontal Crash Test: The majority of injury-causing crashes that occur each year on America's roadways are either frontal or side crashes. Because of this, one of most important tests NHTSA conducts is the frontal crash test. This test simulates a direct head-on collision at 35 miles per hour. The test vehicle is externally driven and crashed into a fixed barrier at 35 mph. The frontal crash ratings of a vehicle can only be compared to those of other vehicles of similar size and weight. These weights may not differ by more than 250 pounds.
  • Side Barrier Test: This test simulates your car being “T-boned” on the driver's side in an intersection by another car. A 3,015 pound movable barrier is crashed into the fixed test car at 38.5 mph.
  • Side Pole Test: This test simulates loss of control of the vehicle resulting in a sideways slide into a telephone pole on the driver's side of the vehicle at 20 mph.
  • Rollover Resistance Test: Each year, more than one-quarter of passenger vehicle crash deaths occur in rollovers, and nearly 85 percent of such fatalities occur in single-vehicle crashes. Because of this, NHTSA tests the rollover resistance of vehicles. This test simulates driving on a 55-mph highway with a sharp curve during which the driver is traveling too fast to navigate the curve and loses control of the vehicle, which departs the road and rolls over. NHTSA's rollover test determines how well a vehicle resists rolling over in severe turning maneuvers, and vehicles with a higher number of stars are less likely to roll over in this scenario.

The results of these tests, along with information about the 5-Star Safety Ratings Program and vehicle safety features, are available at NHTSA attempts to test all models, but funding prevents 100 percent coverage.


The Insurance Institute for Highway Safety (IIHS), funded by the insurance industry, performs its own independent crash testing. In general, IIHS tests are seen as more severe than those performed by NHTSA. To determine crashworthiness, IIHS rates vehicles good, acceptable, marginal, or poor, based on performance in five tests: moderate overlap front, small overlap front, side, roof strength, and head restraints. In the area of crash avoidance and mitigation, IIHS assigns vehicles with available front crash prevention systems ratings of basic, advanced, or superior, based on the type of system and performance in track tests. Unfortunately, IIHS is not able to test all car models, but they do test high-volume vehicles and those that display new or novel technology.

The five tests include:

  • Moderate Overlap Frontal Test: In this test, a vehicle travels at 40 mph toward a barrier with a deformable face made of aluminum honeycomb. The barrier face is just over 2 feet tall. A Hybrid III dummy representing an average-size man is positioned in the driver seat. Forty percent of the total width of the vehicle strikes the barrier on the driver's side. The forces in the test are similar to those that would result from a frontal offset crash between two vehicles of the same weight, each going just under 40 mph.
  • Small Overlap Frontal Test: In this test, a vehicle travels at 40 mph toward a 5-foot-tall rigid barrier. A Hybrid III dummy representing an average- size man is in the driver seat. Twenty-five percent of the width of the vehicle strikes the barrier on the driver side.
  • Side Testing: A 3,300-pound barrier (designed to mimic an SUV) hits the driver's side of the vehicle at 31 mph. Two dummies representing small women or 12-year-old children are positioned in the driver seat and the rear seat behind the driver.
  • Roof Strength Test: In this test, the strength of the roof is determined by pushing a metal plate against one side of it at a slow but constant speed. The force applied relative to the vehicle's weight is known as the strength-to-weight ratio. The peak strength-to-weight ratio recorded before the roof is crushed 5 inches is the key measurement of roof strength. A good rating requires a strength-to-weight ratio of at least 4. In other words, the roof must withstand a force of at least four times the vehicle's weight before the plate crushes the roof by 5 inches. For an acceptable rating, the minimum strength-to-weight ratio is 3.25. For a marginal rating, it is 2.5. Anything lower than that is poor.
  • Head Restraint Test: If a head restraint isn't behind and close to the back of an occupant's head, it can't prevent whiplash in a rear-end collision. IIHS evaluates the geometry of head restraints in passenger vehicles based on the height and backset relative to an average-size male. A restraint should be at least as high as the head's center of gravity, or about 3.5 inches below the top of the head. The backset, or distance behind the head, should be as small as possible. Backsets of more than about 4 inches have been associated with increased symptoms of neck injury in crashes. IIHS classifies each restraint according to its height and backset into one of four geometric zones–good, acceptable, marginal, or poor. A government standard in effect since 2010 requires a minimum of 29.5 inches from an occupant's hip to the top of a head restraint and a backset of 2.2 inches or less. This guarantees that nearly all new head restraints would be rated good for geometry by IIHS.

Seats and head restraints with geometry rated good or acceptable are tested in a simulated rear impact conducted on a sled. The test assesses how well the seats support the torso, neck, and head of a BioRID dummy. The test simulates a rear-end crash approximately equivalent to a stationary vehicle being struck at 20 mph by a vehicle of the same weight.


In this Insurance Institute for Highway Safety crash test of a Nissan Murano, the driver’s space was maintained well, and risk of injuries to the dummy’s legs and feet was low. Insurance Institute for Highway Safety photo

Crash Avoidance Technology

More and more cars are performing well in NHTSA and IIHS tests as manufacturers improve the designs of their products. The next frontier in vehicle safety is to design vehicles that avoid collisions altogether. These technologies are evolving rapidly. For example, one very effective technology is vehicle stability control (VSC). These systems use sensors to determine if the vehicle is following the path the driver intends and if not, use throttle mitigation or activation of one or more brakes to bring the vehicle back in line. This technology is so effective that NHTSA mandated it for all new cars starting in the 2012 model year.

Ultimately, collision avoidance technology will lead up to the so-called automated vehicle, cars that drive themselves, eliminating human error, which by many estimates is at least partly responsible for around 90 percent of collisions. Short of full automation, automakers are producing quite a few technologies on today's vehicles that hold promise to reduce the frequency of collisions. These technologies include:

  • Blind-Spot Monitoring uses radar or cameras to detect cars that are in the left and right lanes beside and behind your vehicle. The system alerts you so that you don't make an unsafe lane change and possibly collide with another car. When a car is in your blind spot, a small icon–typically in your car's side mirror–lights up. If you put on a turn signal while a car is in your blind spot, the light flashes and a warning tone sounds. Blind-spot monitoring may also have a cross-traffic alert function, which is useful when you're backing out of a head-in parking spot. Sensors provide audible or visual alerts if traffic is coming from either direction.
  • Backup camera/sensor systems detect obstacles behind the car when backing out of a parking space. NHTSA has found so much promise in rear-view cameras that they will be required on new cars starting in May 2016 with full compliance required by May 2018.
  • Lane-Departure Warning/Lane-Keeping-Assist Systems use cameras or sensors mounted near the rearview mirror to read road markings–such as painted lines and raised pavement markers–to help you stay in your lane. If your vehicle starts to drift out of its lane, the system alerts you with a sound, a flashing icon on the instrument panel, a pulsing or vibration in the steering wheel or driver's seat–or a combination of all three. Lane-keeping-assist systems go even further. When you start to drift out of your lane, the system nudges the steering wheel or selectively brakes a single wheel to direct the car toward the center of the lane. These corrections are subtle, and you can always override them by turning the wheel yourself.
  • Drowsy-Driver Alert systems use cameras to monitor a driver's head and face, looking for telltale movements, such as slackening in facial muscles or changes in eye-blinking patterns, to detect whether they're nodding off. If the system senses these “microsleeps,” it will let you know, usually with an audible and visual alarm, and sometimes with a vibration in the seat or steering wheel. Some cars even generate computerized “driver profiles” over time. If the car senses any departure from your normal driving patterns–such as falling asleep–it alerts you.
  • Adaptive Cruise Control (ACC) typically uses radar or cameras to detect vehicles ahead of you and then automatically adjusts your speed to maintain a safe distance from them. With most ACC systems, you can even adjust the gap or following distance from the vehicle in front of you to a comfortable range (within limits). And if a car moves into your lane in front of you, or if the car in front of you slows down or speeds up, your vehicle will make the adjustment, keeping a safe distance all the while. If the car in front moves out of your lane, your car will accelerate to and maintain the set speed.
  • Forward-Collision Warning/Collision Mitigation combines an ACC system with audible and visual alerts that warn drivers of a potential crash if they don't begin braking. Collision-mitigation systems alert the driver to the likelihood of crash, automatically apply the vehicle's brakes, and retract and tension the occupants' seatbelts to reduce potential injuries from a crash.

Use the Information to find a safe car

So which car is the safest? AAA recommends that you look at models: with high scores or ratings from NHTSA and IIHS; are the largest (heaviest) and still meet your transportation, performance, and fuel efficiency needs; and are equipped with all or most of the advanced collision avoidance technologies above. NHTSA's website, lists the availability of most of these technologies for current model vehicles.

AAA also publishes its annual AAA Green Car Guide which reviews battery electric, hybrid, alternative fueled, clean diesel, and conventional gasoline-fueled vehicles with exceptionally low emissions (PZEV) or category leading fuel efficiency. Crashworthiness is one of the 13 evaluation criteria used in the guide and the NHTSA crash ratings are published for each vehicle (if available). A vehicle's AAA Green Car Guide crashworthiness score (rated on a 1 to 10 point scale) is calculated based on the weight of the vehicle and the number of air bags. The maximum score based on weight is 5 points, and a vehicle also is awarded points based on its number of air bags, with a maximum of five points possible. The two scores for weight and number of air bags are added together to obtain an overall crashworthiness score.

Remember, despite all of the advances in vehicle safety, the best way to protect yourself in a crash is to wear your seat belt. This simple task can be more effective at saving your life than any other single feature, so buckle up.

September/October 2015 Issue

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