The active vehicle barrier system, or pop-up barrier, is designed to physically prevent unauthorized vehicles from entering Joint Base Andrews. The pop-up barriers are hydraulic, manually operated, systems that deploy in just over one second. As a safety feature, there are light systems immediately next to each barrier. These lights flash yellow when the barriers are completely down. When you see the flashing yellow light, proceed with caution at a reduced speed. If the light is red, stop immediately! The steady red light means the pop-up barrier has been activated. DO NOT PROCEED. Wait until the light returns to a yellow flashing before proceeding. If stopped at a light, DO NOT STOP ON THE BARRIER SYSTEM. These barriers deploy with enough force to lift your vehicle off the ground. Please contact the Antiterrorism Office at 240-612-6313 with any questions or for additional information. We look forward to protecting you, while together we defend America.