The Economics of Clean Air
Odd-Even and Emergency Measures
How Delhi's odd-even car rationing, construction bans and smog towers worked as emergency measures, what research found, and why short-term fixes aren't enough.
When pollution spikes, cities try emergency measures.
Odd-even
- Delhi tried odd-even car rationing in 2016 and later years: cars with odd or even number plates could drive on alternate days.
- Studies found modest effects: some reduction in pollution during certain hours, but much smaller than hoped, as cars are only one source.
Construction bans
Stopping construction reduces dust, but hurts daily-wage workers.
Smog towers
- Delhi installed smog towers in 2021 to filter air.
- Experts said they clean only a tiny area and are not cost-effective.
Cloud seeding
Delhi tried cloud seeding to induce rain in 2025, with limited results.
Truck bans
Restricting diesel trucks from entering the city.
Lesson
Emergency measures can reduce peaks but can’t replace year-round controls on major sources.
A giant smog tower in central Delhi filters air in its immediate surroundings, but the air a few hundred metres away remains polluted.
They reduce peaks but not year-round sources.
- Odd-even had modest effects.
- Construction bans hurt daily-wage workers.
- Smog towers are not cost-effective.
- Year-round source controls are needed.
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