All four managed to earn top 'good' ratings in frontal, side, and rear impact tests, as well as in the roof strength test—and at least an 'acceptable' score in the new IIHS small overlap frontal test—adding up to Top Safety Pick+ status in each case.
However the 2013 Honda Civic and 2013 Volvo XC60 stand above those other two models, in achieving top 'good' ratings in the small overlap test, too—a qualification that the IIHS might require for Top Safety Pick+ status in future model years.
As the IIHS notes, both Honda and Volvo made accommodations for 2013—structural for the Civic and related to airbag deployment in the XC60—to perform better in the new crash test, which measures cabin intrusion and occupant forces in an impact that simulates a particularly deadly or injurious type of accident, when the corner of the vehicle hits a utility pole or another vehicle. The IIHS test is run at 40 mpg, with the vehicle hitting a rigid barrier that overlaps with 25 percent of the front end.
2014 Mazda Mazda6
As for the Lincoln MKZ (for which the IIHS extended results from an earlier test of the closely related 2013 Ford Fusion SE), it did a bit better, with top 'good' ratings in all injury measures although 'acceptable' scores in the structural and kinematics/restraints categories.
The Top Safety Pick+ list remains quite exclusive for 2013, with a total of just 18 models qualifying for the new top tier at this time. More models are slated to be tested before the end of the model years, however, including a batch of compact crossovers later this month.