The Insurance Institute for Highway Safety named its Top Safety Pick+ for 2015.

"This is the third year in a row that we are giving automakers a tougher challenge to meet. The quest for Top Safety Pick and Top Safety Pick+ awards is driving improvement in the small overlap front crash test and getting manufacturers to offer automatic braking technology on more and more vehicles," said Insurance Institute for Highway Safety President Adrian Lund in a statement.

The Insurance Institute for Highway Safety says there are more safe cars on the road this year than last year. The number of vehicles that nabbed their Top Safety Picks jumped from 39 to 71 from last year. The Top Safety Pick+ vehicles rose by 11 for 2015.

The 2015 Top Safety Pick+ designation is awarded to vehicles that meet the Top Safety Pick criteria and also earns an advanced or superior rating for front crash prevention systems. Vehicles have to be able to stop or slow down without driver intervention before hitting a target in IIHS tests at 12 mph, 25 mph or both for an advanced or superior rating.

This year the Insurance Institute for Highway Safety had a tougher standard for front crash prevention. For 2014, vehicles could qualify for Top Safety Pick+ with only a basic rating for front crash prevention. Warning systems that meet the National Highway Traffic Safety Administration's performance criteria but don't include autobrake qualify for a basic rating. For an advanced or superior rating, vehicles must stop or slow down without driver intervention before hitting a target in IIHS tests at 12 mph, 25 mph or both (see "First crash avoidance ratings under new test program: 7 midsize vehicles earn top marks," Sept. 27, 2013).

Because of this change in criteria for 2015, 15 vehicles that qualified for 2014 Top Safety Pick+ are now simply Top Safety Pick winners. In all, there are 33 Top Safety Pick+ winners and 38 Top Safety Pick winners.

The Honda CR-V, a 2015 Top Safety Pick+ winner was modified for improved protection. The Toyota Prius v, which also earns Top Safety Pick+, saw even greater improvement.

Most of the Top Safety Pick+ winners earn the award only when equipped with optional front crash prevention systems. However, when not equipped, they still meet the crashworthiness criteria for Top Safety Pick.

After the structure was improved and the side curtain airbag was lengthened, the 2015 Prius v performed well all-around, with low levels of intrusion, good restraint performance and low injury measures.

Currently only three automakers offer standard front crash prevention systems. Volvo models have standard City Safety, a low-speed autobrake system. The Mercedes-Benz C-Class and E-Class have a warning and autobrake system, but the standard autobrake components haven't been tested yet. The Mercedes-Benz M-Class and CLA and the Acura RLX offer standard warning systems. All these vehicles are available with optional systems that earn higher ratings than the standard equipment. The CLA, which earns an advanced rating with its optional system, hasn't been tested for crashworthiness.