The Supreme Court on Monday refused to halt the construction of Delhi Metro's phase-IV, saying any interference would result in a huge escalation of costs. The phase-IV of Delhi Metro will consist of six corridors -- Aerocity to Tughlakabad, Inderlok to Indraprastha, Lajpat Nagar to Saket G Block, Mukundpur to Maujpur, Janakpuri West to R K Ashram, and Rithala to Bawana and Narela. A bench comprising Justices B R Gavai and Vikram Nath noted that there was a provision for planting uprooted trees. No doubt that concern for the environment is an important aspect. However, developmental work like metro railway, which will cater to billions of people and reduce carbon emissions as the number of vehicles on road will be reduced, cannot be ignored, the court said.