You don’t have to watch TV for long before encountering a commercial boasting about a vehicle’s 5-star safety rating. Should you trust in this rating? Yes, but with caveats.
The government has minimum safety standards that cars and trucks must meet. But those standards don’t ensure a vehicle is as safe as it could be. That’s where the National Highway Traffic Safety Administration safety ratings come in. Vehicle shoppers can see the safety ratings on the window stickers of new cars and look up ratings online.
See also: 5 tech innovations making cars safer
The ratings tell you which cars are among the safest, although they don’t necessarily apply for every possible crash or compared with a car in another weight class, and don’t encompass all safety factors.
Testing overview of 5-star safety ratings
Each year, federal officials decide which vehicles to test by looking at which are predicted to have high sales or have been structurally redesigned. They then buy cars for testing from dealerships across the country. The ratings divide vehicles into classes: mini, light, compact, medium and heavy cars, plus sport-utility vehicles, pickup trucks and vans.
The testing started in the 1979 model year, with only frontal crashes. The National Highway Traffic Safety Administration added the star ratings in 1994 (five is the safest), side-impact tests in 1997 and rollovers in 2001.
Big changes came in 2011, when regulators toughened front and side crash ratings criteria, started using a smaller, “female” crash-test dummy in addition to an average-sized male dummy, added a test simulating the side of car crashing into a pole or tree and created a new overall score that combines front, side and rollover ratings. That’s why, if you go to the ratings site now, you’ll find separate areas for vehicles from 1990 to 2010 and from 2011 on.
Entries for specific cars also list whether a car has advanced crash-avoidance technologies (rear-view video, and collision and lane-departure warning systems) that meet federal standards and note any safety concerns, such as structural failure, fuel leakage or a door opening during crash tests.
Limitations of the safety tests
Despite the overhaul that started with 2011 models, the 5-star safety ratings still don’t present a complete overview of safety. For one thing, crash-avoidance technologies and specific safety concerns do not factor into the star ratings, so you have look at each vehicle’s record to find them.
Also, the frontal-crash ratings are only comparable between cars that are in the same class and weigh within 250 pounds of each other. That’s because this test represents a crash between two vehicles of the same weight, so lighter cars are not rated on how their passengers would do in a crash with a heavier vehicle (the other tests are comparable across classes).
The testing doesn’t include rear impacts. The National Highway Traffic Safety Administration says that’s because the program has a limited budget, and frontal and side-impact crashes “are responsible for the highest percentage of deaths and serious injuries.”
The tests only look at specific injuries to passengers in specific seats:
For the frontal crash, injuries to the head, neck, chest and legs of an average-sized adult male driver and small adult female front-seat passenger;
For the side-barrier test, injuries to the head, chest, abdomen and pelvis of an average male driver and a front-seat passenger, and to the head and pelvis of a small female passenger in the rear, driver’s-side seat;
For the side-pole test, injuries to the head and pelvis of a small female driver and a front-seat passenger.
The tests do not evaluate injuries to children.
The tests are all at specific speeds: 35 miles per hour for the frontal crash, 38.5 miles per hour for the side-barrier crash and 20 miles per hour for the side-pole crash. How a vehicle does in these may or may not translate to a faster impact.
Proposed changes to 5-star rating system
In December 2015, the National Highway Traffic Safety Administration proposed more changes to its testing and rating system. These include:
Adding crash-avoidance systems to ratings;
Testing and rating how well vehicles protect pedestrians they might strike;
Testing of angled frontal crashes;
Testing protection of rear occupants in a frontal crash;
Improved crash test dummies; and
“The changes provide more and better information to new-vehicle shoppers that will help accelerate the technology innovations that saves lives,” U.S. Transportation Secretary Anthony Foxx said in a news release. Officials plan to adopt the changes by the end of 2016 and implement them by the 2019 model year.
For now, the current 5-star rating system will tell you if a car is among the safest in its class, although not in every possible situation, and you’ll have to look at a specific vehicle’s entry to see if it has advanced crash-avoidance features or special safety concerns. You should also check out ratings from the Insurance Institute for Highway Safety, which carries out its own tests.
See also: Teen wheels: Is that junker safe?