As detailed in my book Toxic Capitalism, the issue of the air pollution in Beijing is serious but also complicated.
What happened during the run-up to the 2008 Olympics is another story; I was deeply involved in following that story, how Beijing was forced to take draconian measures – something that was only possible then and cannot be copied. I plan to write about that in detail one day. I talk about that in seminars I organize.
Car emissions are believed to account for one-third of PM2.5, a major air pollutant, in most congested areas in Beijing. Studies suggest a quarter of the pollutants in the city’s air comes from its surrounding areas.
Contrary to what some people believe abroad, the city government is pretty aware of the dramatic increase in air pollution and is now intensifying efforts to reduce the PM2.5. They have little choice as the population is too aware of the severity of the pollution and has even forced the authorities to start monitoring PM2.5.
See here the main points in the action plan. See the pdf for the full details and the sources (China Daily): 130903 BJpollution

Highlights – Beijing’s action plan on clean air
Five-year plan 2013-2017

• To reduce PM 2.5 density by 25% or more by 2017 with PM 2.5 density controlled to around 60 micrograms/m3, a 25% drop from 2012 levels.
• To slash 13 million metric tons of coal consumption over five years (more than 50%) based on 2012 levels; to reduce the proportion of coal used within the city’s total energy mix to below 10%. Coal consumption to be less than 10 million T by 2017.
• To completely eliminate the use of coal within the Second Ring Road.
• Vehicles from outside Beijing will be forbidden from entering the Sixth Ring Road unless with permission.
• To control private car ownership within 6 million by the end of 2017, from more than 5.2 million as of early 2013.
• Vehicle fuel use to be cut by at least 5% in 2017 from 2012 levels.
• One million old polluting vehicles to be scrapped from 2013 to 2017.
• A congestion charge would be levied mainly on vehicles in the downtown area and will be set out in the near future by the Beijing Environmental Protection Bureau and Beijing Commission of Transport.
• Public transportation in central Beijing to account for 52% of all trips in 2017.
• More than 65% of public vehicles to be clean energy vehicles by 2017.
• More than 60% of the city to be covered by green space by the end of 2017.
• Area of Beijing covered by water to increase 1000 hectares from 2013 to 2017.

Do note this is only part of the story. Not mentioned here are a series of other measures, including the improvement of car fuel (gasoline / diesel), e-vehicles, etc. See earlier posts.