It's a fact of physics: Larger vehicles are safer than smaller vehicles. But not everyone is cut out to drive a large car. Small cars are less expensive, easier to park and get better fuel economy than larger ones. And with gas prices on an upward creep, consumers shopping for a fuel-efficient vehicle are already gravitating toward smaller cars. But by doing so, will they put themselves at risk in an accident? There's bad news and good news on this front.
The bad news is that smaller, lighter cars are generally not as safe as larger, heavier cars. Large vehicles have longer hoods and bigger crush zones, which gives them an advantage in frontal crashes.
In studies conducted by the Insurance Institute for Highway Safety (IIHS), a heavier vehicle will typically push a lighter one backward during the impact. As a result, there will be less force on the occupants of the heavier vehicle and more on those in the lighter vehicle, according to IIHS.
Improvements in Small Car Safety
The good news is that small cars are safer than ever. Indeed, every vehicle size category has seen a substantial decrease in fatalities over the past six years.
"Historically, the rates of driver deaths per million registered vehicles have been higher for the smaller and lighter vehicles. This was true again in 2011, but the differences were less extreme than they used to be," concluded an IIHS report.
The keys to a car's ability to keep you alive during a crash involve safety equipment, the vehicle's weight and its resistance to rolling over. While small cars don't roll over easily, they lack weight and, until recently, were less likely to have advanced safety features like electronic stability control (ESC) or full side airbags. ESC has become an increasingly common feature over the past few years and is now required standard equipment on every 2012 and newer vehicle. And as of the 2012 model year, side airbags were standard on 84 percent of vehicles.
The charts below compare 2005 and 2011 fatality rates for the different vehicle sizes.
|Driver deaths per million registered passenger vehicles 1-3 years old, Source: IIHS|
|Vehicle Size||Rate (2005)||Rate (2011)|
According to the 2011 IIHS figures, fatalities per million registered vehicles decreased 55 percent for the mini car category and 47 percent for the small car category. There was a 51 percent decrease in fatalities for midsize cars and 45 percent for large sedans.
Smaller cars have benefitted from advances in structural materials, says Chuck Thomas, chief engineer of Honda's automotive safety research facility in Ohio.
"There are many new materials that are available to us now, such as hot-press steel, that were not available in the early 2000s," Thomas says. Honda has integrated those materials into its vehicles to improve their structure and keep the space around the occupants protected, Thomas says.
And to help reduce injuries in accidents involving cars of different sizes, Honda in 2005 developed a safety technology called "Advanced Compatibility Engineering" (ACE, now ACEII on newer vehicles), which disperses the impact forces of a frontal collision. On smaller cars with ACE, there is more reinforcement on the upper portion of the hood, where a larger vehicle would be more likely to strike it.
SUVs Are Safer Now
In the SUV category, the fatality rate dropped substantially across all size levels. Midsize and large SUVs fared the best, with 16 and 14 deaths per million, respectively. Midsize SUVs improved by 72 percent from 2005, while large SUVs saw a 71 percent improvement.
SUVs benefit by being taller, and thus are less likely to slide under another vehicle in a crash (a situation called "underride"). But in the past, SUVs had some of the highest death rates because they were prone to rollover crashes, and that tendency outweighed any size advantage.
"The problem with old SUVs [where ESC was an option or not available] is that while they have the advantage of size and weight, that benefit is offset by their greater propensity to roll over in crashes," says Russ Rader, senior vice president of communications for the IIHS. "The rollover problem has been greatly reduced by ESC, which is now standard on all passenger vehicles, and new SUV designs that are more carlike and less top-heavy."
The exception to the bigger-is-better rule comes with pickup trucks, because of their tendency to roll over. Still, ESC has helped decrease the fatality rate in pickups significantly over the past six years, Rader says.
For all categories, it's important to put the fatality figures into perspective. They describe the differences per million registered vehicles, so no matter what size vehicle you are in, your chances of dying are relatively small, while your chances of surviving a crash are improving over time.
"Crash fatality rates for all vehicle sizes are dropping from year to year," said Rader.
One thing that can cloud the safety picture for car buyers is the fact that cars of various sizes can win identical safety ratings, making it seem that a small car is just as safe as a large SUV. But it's not so.
The federal government has its Five-Star Safety Ratings, which are available at the Safercar.gov site, administered by National Highway Traffic Safety Administration (NHTSA). IIHS does its own crash tests and rates cars from "Good" to "Poor," based on the driver's ability to survive a crash.
It's important for car buyers to keep in mind that these ratings are only useful when comparing cars within the same size class. If a small car has a five-star rating from NHTSA, that doesn't mean it will protect you as well as five-star-rated large sedan. The same holds true for an IIHS "Good" rating.
"The ratings are meant to be used to compare crashes with vehicles of similar size," says Adrian Lund, president of the IIHS. "You can't really go between the segments with these ratings."
IIHS produced this video in 2009 to illustrate the differences in what happens to different-size cars in a crash: The smaller car loses. As Lund says in the video, "While all cars have gotten safer in recent years, you can't repeal the laws of physics."
No crash-test program can cover every car accident scenario, but if you buy a car that scores well in the IIHS and NHTSA tests, your chances for avoiding serious injury or death significantly improve, regardless of the vehicle's size. This is good news for the small-car buyer who is looking for good fuel mileage as well as safety.
But if you were traveling in a car that was rated "Poor" and got hit by a car rated "Good" in an accident that could produce fatalities, you would be four times more likely to be killed than the other driver, according to a 2005 IIHS study. The vehicles compared were of similar size and weight. Numbers from NHTSA also bear this out: The lower a car's crash-test rating, the more likely you are to be seriously injured in an accident.
Old vs. New
To recap: All cars are getting safer, but bigger cars still are safer than small cars. That applies even in a matchup between a new small car and a 5-year-old larger car.
"The bottom line is that bigger and heavier is still better," Rader says. "A heavy, large car from five years ago, given similar safety equipment like side airbags, will be more protective than a 2013 model that is small and lightweight." Because of the tendency to roll over, a 5-year-old SUV would probably trump a new small car only if the SUV had electronic stability control.
Regardless of what you drive, all experts agree that how you drive is the most important safety factor. Human performance and behavior factors contribute to more than 90 percent of vehicle crashes, according to NHTSA. For more information on improving your safe driving skills, see this article: "What To Look for in an Advanced Driver-Training Class."
To find a dealership that knows how to treat shoppers right, please visit Edmunds.com's Dealer Ratings and Reviews.