4 of the safest cars you can buy

The definition of a safe car is expanding to include not only keeping you safe in a crash but aiming to avoid the crash altogether. The Insurance Institute for Highway Safety (IIHS) has given its first top safety rating of 2016 to three sedans and a luxury SUV.

The Honda Civic, Hyundai Sonata, Nissan Altima and the Lexus RX 350 SUV all earned the maximum Top Safety Pick Plus designation.

To get a Top Safety Pick Plus rating, a vehicle must get a score of "Good" in crash tests that cover front and side impact and rollover accidents. In addition, it must also offer accident prevention systems such as automatic braking that are rated "Advanced" or "Superior." If a vehicle passes the crashworthiness tests but has an accident prevention system rated only as "Basic," it gets a second-tier Top Safety Pick rating.

The rules for getting a Top Safety Pick Plus designation have tightened for 2016. Before, a car could earn this rating with just an "Acceptable" score in the difficult small-overlap front crash test, which simulates hitting a tree or utility pole with the corner of the vehicle. Now that rating must be "Good" -- the same as for the other four crash tests.

Let's have a closer look at the first four vehicles of the new year to get the Institute's top safety rating.

Honda Civic Sedan

The 2016 Honda Civic was named North American Car of the Year earlier this month at the Detroit Auto Show. Reviewers surveyed by U.S. News praised the Civic for a quiet ride and an interior with premium materials and spacious rear seats. The Civic comes with a base 2-liter four-cylinder engine rated for 31 MPG in city driving and 41 on the highway. An optional 1.5-liter turbocharged four-cylinder with better acceleration gets an estimated 31 city, 42 highway.

In the safety tests, the redesign boosted the compact Civic sedan up from a second-tier Top Safety Pick (minus the Plus) in the 2015 model. In addition to top ratings in all crash tests, its automatic braking system avoided crashes simulating a collision with the vehicle ahead at both 12 MPH and 25 MPH. The Civic also has a warning to alert the driver to an imminent collision.

Hyundai Sonata

The 2016 Sonata has only minor styling changes from the seventh-generation redesign last year. Reviewers praised the Sonata for its upscale interior and roomy seats and easy-to-use audio and climate controls. A seven-inch touch screen is now standard along with a rearview camera. Cargo space also is roomy compared to other midsize sedans.

The 2.4-liter four-cylinder base engine is rated for 25 MPG in city driving and 38 on the highway. The turbocharged Eco model, which test drivers say offers better acceleration, also has high estimated fuel economy at 28 city, 38 highway.

The crucial addition for the IIHS top safety rating was the automatic emergency braking system. The Institute said the Sonata's system avoided collisions in tests at both 22 MPH and 25 MPH.

Hyundai made safety improvements to the Sonata after production had begun on the 2016 model year. As a result, the top safety rating applies only to Sonatas produced after October, 2015. (The date of manufacture appears on a plaque on or near the driver's door.)

Nissan Altima

Steering and suspension changes in the 2016 Altima have sharpened the handling in a car that already was considered among the nimblest of midsize sedans. Reviewers say the standard 2.5-liter four-cylinder engine -- EPA rated at 27 MPG in city driving, 39 on the highway -- has adequate acceleration. But they prefer the brisk pace of the 3.5-liter V-6, rated 22 city, 32 highway.

In the safety tests, the Altima's automatic braking system was the only one among these four vehicles that did not avoid a collision at 25 MPH. But its successful avoidance at 12 MPH and a reduction in its impact speed of 10 MPH in the faster test were sufficient to gain it the top safety rating.

Lexus RX 350

This redesigned luxury SUV garners praise for its smooth ride and terrific interior comfort. The main negative to reviewers is that the RX 350 doesn't match the acceleration and handling of some competitors. The RX 350 comes with a 3.5-liter V-6 rated for 20 MPG and 28 on the highway. If you opt for the all-wheel-drive version, those numbers drop to 19 city, 26 highway.

Standard features on the RX 350 include an eight-inch touch screen and voice recognition for the infotainment system as well as separate climate controls for driver and passenger and a rearview camera.

In the safety tests, the automatic braking on the RX 350 successfully avoided collisions at both 10 MPH and 25 MPH. The collision avoidance system also includes a warning that sounds if a front-end collision is imminent.