http://www.ritehite.com/products/other/barrier-systems/safe-t-gate/safe-t-gate-automatic

Even when dock doors are closed, they are no match for most
material handling equipment.

The latest safety innovation from Rite-Hite, the Safe-T-Gate Automatic
Barrier System provides loading dock drop-off protection with the push
of a button.
Obstructions are detected by the operator and photo eye, allowing
the Safe-T-Gate to operate safely and trouble free. Interlocking the
Safe-T-Gate with other loading dock equipment is available to ensure
the safest sequence of operation.
Thirty-inch high, quarter-inch thick steel Wardens provide protection for
the tracks of both the Safe-T-Gate and overhead door when the barrier is
raised.

This flexible, unique design withstands inadvertent impacts with little or
no damage, and can stop a 10,000 load at 4 m.p.h.

For more information about loading dock barriers visit http://www.ritehite.com/products/other/barrier-systems