BEIJING -?A Beijing traffic management official has ruled out offering free bus rides for residents on bad air quality days.

The free ride proposal has been floated for sometime as a way to discourage Beijingers from driving cars -- a contributor to the city's air pollution.

Rong Jun, an official with Beijing Municipal Transportation Commission, told delegates attending the city's annual congressional meeting that the authorities would not roll out such a policy anytime soon.

He said Beijing's public transport system is operating under stress, handling 11 million passengers in a day. Any abrupt change of policy would bring with it great risks and threatens the safety.

Rong also said there was no timetable for congestion fees. The plan is still being studied.

Beijing is a victim of emission-induced air pollution that frequently hits north China. The city is home to 5.7 million vehicles. Restrictions are in place to curb further growth of the figure.

Beijing has invested heavily in subway and urban rail lines. This year there is 600 kilometers of track under construction.