"We are planning to bring legislation to convert 40,000 diesel commercial vehicles to CNG mode to decrease air pollution in the capital," Dikshit told reporters.
The chief minister said the environment department would chalk out a plan to put up hoardings to the effect on all busy road intersections.
"The legislation will come soon," Dikshit said in reply to a question on when she would bring a bill for approval in the assembly.
The environment department would be holding street plays at 40 places for creating awareness on air pollution.
Dikshit said: "The number of vehicles is increasing day by day, which shows the prosperity of citizens. But it is also increasing pollution levels. This leads to asthma, bronchitis, heart attacks and deafness due to noise pollution beyond the 125 decibel level."
According to the Centre For Science and Environment (CSE), the market share of diesel cars has already increased to over 30 percent in the last 18 months. The share of diesel cars is expected to rise to 50 percent of total car sales by 2010.
"This growth in personal diesel vehicles will undo all the efforts to reduce pollution by phasing out diesel buses and converting them to CNG," said Anumita Roy Choudhury, head of CSE's air pollution campaign.
She said diesel vehicles emit more smoke, particles and nitrogen oxide than petrol-driven vehicles.
In 2002, the city buses were converted to CNG mode. But with a huge growth in the number diesel-driven private cars, the situation is returning to the pre-2000 level, she said.