The judges listed a series of measures that have been taken over the years apart from the two-phase odd-even. These steps include a ban on registration of diesel vehicles over 2000cc, an environment compensation charge on trucks plying through the city and a CNG requirement for public transport vehicles and taxis.

Is Delhi neglecting some causes and overemphasising on others? Does the approach need a change? TOI reached out to scientists and public health experts to understand how strategies could be prioritised, and what the new approach could be. A majority of experts do not consider vehicular pollution to be the number one cause of pollution--road dust and poor approach to construction are rated as the top causes.

The responses TOI received suggested two approaches -controlling the major emission sources and reducing exposure to the nearest or immediate sources of pollution to reduce health risks.

Overall emissions could be reduced by interventions, such as leapfrogging to EuroVI fuel norms, finding a foolproof solution to biomass burning, covering open spaces with grass and improving public transport.

Two public health experts--Melina S Magsumbol of the Public Health Foundation of India (PHFI) and Anumita Roy Chowdhury , member of health ministry's steering committee -suggested a slightly different approach. Magsumbol, for instance, said: "The odd-even scheme is a way of avoiding congestion and heavy traffic but it is not sustainable unless better public transport options are available...people need targeted health information - for example, those highly at risk are the elderly , pregnant women and children. They should be advised on when to be outside when playing or exercising," she said.

She suggests different policies for different seasons. This was highlighted by IIT-Kanpur in its recent report where vehicles and biomass burning were dominant problems in winter while road dust gained proportions in summer. Roy Chowdhury suggested that "the ranking of pollution sources will have to take into account not only the quantum of pollution but also toxicity of pollution and our proximity to pollution sources to prioritise action. Vehicles receive the top rank because, in urban areas, we are closest to vehicles and their emissions are much more toxic than natural dust."

Manju Mohan, professor at IIT-Delhi, said her research had proved that "regional transport" of pollutants and meteorological factors played a very important role in accentuating pollution --biomass burning in neighbouring states and industries did add to Delhi's suffering so the policies might have to be broadbased to neighbouring states.