Are Small Cars Safe?

"Are small cars safe?" "Are heavy older cars safer than light new ones?" "If a small car gets a good crash test score, does that mean it will hold its own in a crash with a bigger car?"

These are questions we often hear from car shoppers. Some want to downsize to a more compact vehicle. Others are searching for an affordable but safe car for their newly licensed teenagers. Here are quick answers to those questions, and some more detail about small-car safety.

Bigger Cars Are Safer Than Smaller Ones

New small cars are safer than they've ever been, but new larger, heavier vehicles are still safer than small ones. It's a matter of physics: Bigger and heavier is safer than smaller and lighter. Large vehicles weigh more and have longer hoods and bigger crush zones, which gives them an advantage in frontal crashes.

In its studies, the Insurance Institute for Highway Safety (IIHS) has found that a heavier vehicle will typically push a lighter one backward during the impact. As a result, there is less force on the occupants of the heavier vehicle and more on those in the lighter vehicle, according to IIHS. The organization's fatality data bears this out. The lowest 2015 death rate by vehicle type is for very large SUVs: 13 deaths per million registered vehicles. The highest is for mini cars: 64 deaths per million registered vehicles.

Older 'Tanks' Are Not Safer Than Smaller New Cars

Some people contend that older cars were built like tanks, making them safer than new cars. It's not true.

A large 10-year-old vehicle that does not have side airbags or electronic stability control (ESC) would not fare as well in an accident as a small vehicle from today equipped with modern safety equipment and collision avoidance technology, said Becky Mueller, senior research engineer for IIHS. ESC greatly reduces the chance of a vehicle rollover, which is particularly important for top-heavy trucks and SUVs, according to IIHS.

That said, not everyone is able to buy new. So if you're shopping for a used car, make sure it has side airbags and ESC, Mueller said. In many cases, these were optional features on smaller and non-luxury vehicles.

Crash Test Scores Don't Compare Across Size Classes

One thing that can confuse car buyers is that cars of various sizes can carry identical safety ratings, making it seem that a small car is just as safe as a large SUV. It's not so.

The National Highway Traffic Safety Administration (NHTSA) has its five-star safety ratings. IIHS does its own crash tests and rates cars for crashworthiness from Good to Poor, based on the driver's ability to survive a crash.

These ratings are only useful when you're 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 a Good rating from the IIHS.

"The ratings are meant to be used to compare crashes with vehicles of similar size," said 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 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 mileage as well as safety.

How Cars Got Safer

Over time, all vehicles have benefited from safety advances. Starting in the 2012 model year, for example, ESC became mandatory in all vehicles. Carmakers also installed more airbags and strengthened the roofs of SUVs and trucks, which sometimes had lacked sufficient roof strength to protect occupants in a crash. Most recently, active safety technology has brought automatic emergency braking and forward collision warning systems to many cars, preventing them from getting into accidents in the first place. As a consequence of these changes, every vehicle size category has seen a substantial decrease in deaths over the past 10 years.

A Decade of Improvement

The chart below compares 2005 and 2015 fatality rates for the different vehicle sizes. 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. According to 2015 IIHS data, deaths per million registered vehicles decreased 56 percent for the mini-car category from 2005 to 2015. Deaths dropped 57 percent in small cars, 46 percent in midsize cars and 28 percent in large sedans.

Should We All Be Driving SUVs?

Despite rollover and roof issues, SUVs have long been the safest category, and that trend continues. SUVs benefit by being taller, and thus they are less likely to slide under another vehicle in a crash — a situation called "underride." Large and and very large SUVs fared the best in 2015 data, with 14 and 13 deaths per million, respectively. The death rate in large SUVs decreased by 71 percent over 10 years, while the popular small SUV class saw a 60 percent decline in the fatality rate.

Now that ESC has become a standard feature, pickup trucks have seen the largest drop in deaths over the past 10 years. Small trucks had a 78 percent decrease in fatalities, large trucks a 63 percent drop.

Within any given vehicle type, bigger is still safer. But that doesn't mean we all have to drive large SUVs. Safety is only one vehicle consideration, along with cost, fuel efficiency and your everyday driving needs. An SUV won't be right for everyone.

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 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."