Subaru has announced that total production of vehicles equipped with its trademark All-Wheel Drive (AWD) system has this month reached 15 million units.

The milestone was achieved almost 44 years after the company introduced the Subaru Leone 4WD Estate Van in September 1972. Since then, Subaru has continuously developed and enhanced its AWD technology.

In 2015, AWD-equipped models accounted for 98% of Subaru’s global sales. Powered by horizontally-opposed ‘boxer’ engines, including, since 2007, in diesel form, all of these AWD models featured the latest version of Subaru’s distinctive Symmetrical AWD system.

Subaru says its Symmetrical All-Wheel Drive offers a combination of superior stability and traction intrinsic to AWD, and the combination of the symmetrical drivetrain with a longitudinally-mounted Boxer engine helps to balance weight distribution.