A fine of $14 - a significant amount in China where incomes are lower than those in more developed countries - will be levied on those who drive their vehicles on the wrong day.
Traffic on the streets of the Chinese capital was light as the restrictions came into force, but it will take some time for the haze to clear.
There are 3.3 million vehicles in Beijing. A package of similar restrictions to reduce their use was introduced for a trial period last August but the haze from pollution remained.
This time, the authorities have also ordered the shutting down of polluting industries in the region around Beijing, as well as the halting of construction in the city.
A day before the road traffic restrictions took effect, Beijing opened three underground railway lines to absorb the amount of extra passengers using the city's rail network.
The Chinese government is taking considerable steps to promote an image of harmony and unity in the run-up to the games.
But concerns remain about government attempts to quell any social unrest.
Two people were killed by police officers during a battle with villagers in southwestern China in the latest incident, an activist group said on Sunday.
About 1,000 rubber growers demonstrating over the price at which they have to sell their crops, clashed with police in Yunnan province's Menglian county on Saturday, the Hong Kong Centre for Human Rights and Democracy said.
The farmers are angry at having to sell their entire crop to local government departments at prices 40 per cent lower than they could obtain on the open market.
Xinhua, China's state news agency, said the local government had been instructed to put an end to the dispute.
It quoted Bai Enpei, a senior Communist party official, as saying that the provincial authorities should listen "attentively to the complaints and appeal of local residents, making great efforts to rescue the injured people, and consoling family members of the dead to prevent the matter from escalating".
China recently ordered local governments to make every effort to resolve social disputes to prevent protests from spreading to the capital.