The “odd-even” formula introduced by the Delhi government last year to temporarily restrict the numbers of vehicles on the capital’s roads reduces pollution in winter but has no perceptible effect in summer, scientists have said.

Their findings suggest that the Delhi government’s decision on Saturday to abandon its plans to impose the odd-even formula for five days next week will deny the capital’s population a small yet significant improvement in air quality, they said.

The Delhi government had imposed the odd-even formula – that uses registration numbers to allow vehicles to ply on odd and even days – twice last year.

“The odd-even scheme would have brought some respite – even if the air pollution levels are lower now than what they were earlier this week,” said Santosh Harish, a policy researcher at the Energy Policy Institute at the University of Chicago’s India centre….