Dense fog claimed at least four lives on Tuesday after seven buses and three cars collided due to low visibility on the Delhi-Agra Expressway in Mathura. Police said the multi-vehicle pile-up led to several
vehicles catching fire after the collision. The accident came just a day after a similar collision on the Delhi-Mumbai expressway when dense fog resulted in a deadly multi-vehicle collision involving approximately 20 vehicles.
Winter months bring the much-dreaded fog to North India, disrupting transport, daily activities, and health across the belt. As mercury dips, northern India experiences very low temperatures, especially at night. As the temperature drops, the air near the ground cools and loses its capacity to hold moisture. This causes water vapour to condense into tiny droplets, forming dense fog. The problem becomes worse because winds are weak in winter, so the fog remains trapped near the surface for long hours.
The Indo-Gangetic plains, which cover much of northern India, provide ideal conditions for fog formation. Moisture from rivers, canals, and irrigated fields increases humidity in the air. When cold air settles over this moist region, fog develops easily. Additionally, air pollution from vehicles, industries, and crop-residue burning mixes with fog, creating thick smog. This makes the fog denser and more persistent, reducing visibility.
While one must avoid travel during low visibility, in case you really need to step out, here are things to keep in mind if you are driving:
1. If visibility is under 50 metres, waiting even 30-60 minutes after sunrise can dramatically improve safety.
2. Always assume a tractor crossing the highway, a truck parked on the lane or a pedestrian walking in dark clothes. Cover your brake and keep reactions gentle.
3. Slow down: Fog kills depth perception. Drive well below the speed limit and be ready to stop within the distance you can see.
4. Use low-beam headlights: High beams bounce light back off the fog and make visibility worse. Use low-beam lights and fog lights.
5. Increase following distance: Double or even triple the normal gap. The car ahead may brake suddenly and disappear into the fog.
6. Use road markings as guides: Focus on lane lines and edge markings, not just the vehicle ahead. They’re more reliable in thick fog.
7. Avoid sudden moves: No sharp braking, no quick lane changes. Be smooth and deliberate so others can predict you.
8. Use wipers and defoggers correctly: Fog often comes with moisture. Keep the windshield clean (inside and out). Use a defogger together with an AC if needed. You can also crack a window slightly to reduce interior fogging.
9. Don’t rely on hazard lights while moving: Hazard lights confuse drivers behind you. Use them only if you’re stopped or nearly stopped due to zero visibility.
10. Lower music volume. You may hear vehicles before you see them, especially at intersections.
11. If visibility drops to near zero, pull over safely. Exit the road if possible and park well off the carriageway. Turn off the headlights and keep parking lights on as headlights can make others think you’re still moving.
12. Stay calm and patient: Fog causes pile-ups because drivers rush to “get out of it”. There’s no shortcut and time and caution are the only way through.
13. Learn truck rules: Trucks do not see well behind in fog. Never cut in front of a truck as braking distance is huge. If following one, keep enough gap to see its rear wheels clearly.
14. Fog causes mental fatigue faster than night driving. Stop every 60–90 minutes, get out, stretch, and hydrate.
15. If you are driving a two-wheeler, avoid early morning fog completely if possible. Wear reflective jacket/tape and ride at half your normal speed. If fog thickens, stop riding as two-wheelers are nearly invisible.
