The Insurance Institute for Highway Safety say 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. "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 criteria for Top Safety Pick haven't change, they still give a good or acceptable rating in the small overlap front test and a good rating in each of the Institute's four other crashworthiness evaluations - moderate overlap front, side, roof strength and head restraints.

The front crash prevention warning systems must meet the National Highway Traffic Safety Administration's performance criteria.

Because of the 2015 criteria change, 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.

"Although forward collision warning on its own is a valuable feature, we decided to tighten our criteria to encourage manufacturers to offer autobrake. Systems that don't require a driver response to avoid or mitigate a crash have the most potential for reducing crashes. Nevertheless, the models that are losing their plus signs are still great choices for safety, as are all the Top Safety Pick winners" Insurance Institute for Highway Safety President Adrian Lund said.

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.

The list of 2015 Top Safety Pick+ winners shows how quickly front crash prevention systems with autobrake are spreading. In total, there are 27 superior-rated 2015 models and 33 with an advanced rating.

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.

Right now, the only carmakers who standard front crash prevention systems are: 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.