The Delhi high court has directed the Municipal Corporation of Delhi (MCD) and the New Delhi Municipal Corporation (NDMC) to clean the city roads during the night. The directions were issued in response to a public interest litigation (PIL) filed by Ravinder Raj, a retired public servant, who said that cleaning of the roads during morning hours was causing air pollution. It is during these hours that most of the people commute. By changing the cleaning hours this problem can be avoided. "The level of suspended particulate matter (SPM) of the city's air is very high. At certain places it reaches levels ten times the permissible limit. Therefore, any activity that contributes towards increasing the SPM levels needs to be discouraged, ' said H B Mathur, professor emeritus at the Delhi College of Engineering. But the civic bodies argue that sweeping the lane and bylanes at night is going to pose problems as they are inaccessible due to haphazard parking of vehicles. Even poor lighting facilities will hamper the effective implementation of the court's order.