The Sidewalk Grates Let the Subway Breathe
Those broad iron grates are openings into the subway’s ventilation system. They allow air to move between underground spaces and the street, helping replace stale air and carry away heat produced by trains, brakes, lights, and other equipment.
Trains Push Air Through the Tunnels
A moving train displaces the air ahead of it and leaves lower pressure behind. In a tunnel, that motion can drive air through connected passages and ventilation openings—a little like a piston moving through a cylinder. The grates provide one route for that air to escape or enter, reducing the buildup of heat and pressure underground.
They work alongside fans and other ventilation equipment; the grates themselves do not ventilate every part of the system on their own. Their placement and size reflect the need to move substantial volumes of air through dense city blocks without closing the sidewalk.
Why the Openings Are So Large
A small vent would restrict airflow. A wide, strong metal cover can span a large opening while supporting the foot traffic above it. That makes the grate part of the subway’s infrastructure and part of the street at once: the sidewalk is also a path for air moving through the transit system below.
