What is the small yellow light on in the tunnel connected to the iron box? On the high speed.

is a small anti-collision artifact in foggy days. The "small anti-collision artifacts" installed on both sides of the expressway warn the vehicles to slow down and pass the roads in foggy areas safely through the warning of "yellow light guiding, red light going slowly". Add flashing lights and oscillating markings at important bridges, tunnels, ramps and bends, add reflective strips to guide the tunnel walls along the line, install lighting facilities on the extra-large bridge, add a set of distance confirmation signs 1-2 kilometers upstream of the starting end of the fog-prone road section, add yellow flashing lights near the underpass of toll station and service area, and set up warning slogans.