![A passenger gestures as he lines up and waits for a security check during morning rush hour at Tiantongyuan North Station in Beijing May 27, 2014. Beijing tightened security checks at subway A passenger gestures as he lines up and waits for a security check during morning rush hour at Tiantongyuan North Station in Beijing May 27, 2014. Beijing tightened security checks at subway](https://c8.alamy.com/comp/2CXN996/a-passenger-gestures-as-he-lines-up-and-waits-for-a-security-check-during-morning-rush-hour-at-tiantongyuan-north-station-in-beijing-may-27-2014-beijing-tightened-security-checks-at-subway-stations-since-last-saturday-following-an-attack-in-chinas-troubled-xinjiang-region-which-killed-31-people-on-may-22-the-deadliest-act-of-violence-in-the-region-in-years-reutersjason-lee-china-tags-civil-unrest-crime-law-transport-2CXN996.jpg)
A passenger gestures as he lines up and waits for a security check during morning rush hour at Tiantongyuan North Station in Beijing May 27, 2014. Beijing tightened security checks at subway
![A traffic policeman on duty looks at vehicles on the 2nd Ring Road during rush hour in Beijing June 20, 2008. Beijing will introduce odd-even traffic restrictions for two months from July A traffic policeman on duty looks at vehicles on the 2nd Ring Road during rush hour in Beijing June 20, 2008. Beijing will introduce odd-even traffic restrictions for two months from July](https://c8.alamy.com/comp/2E756WC/a-traffic-policeman-on-duty-looks-at-vehicles-on-the-2nd-ring-road-during-rush-hour-in-beijing-june-20-2008-beijing-will-introduce-odd-even-traffic-restrictions-for-two-months-from-july-20-to-help-ease-congestion-and-reduce-pollution-during-the-olympics-and-paralympics-the-city-government-said-reutersjason-lee-china-2E756WC.jpg)
A traffic policeman on duty looks at vehicles on the 2nd Ring Road during rush hour in Beijing June 20, 2008. Beijing will introduce odd-even traffic restrictions for two months from July
![Vehicles are seen in a traffic jam on Jianguo Road ahead of the evening rush hour in central Beijing, December 23, 2010. Beijing will limit issuance of new car plates to 240,000 Vehicles are seen in a traffic jam on Jianguo Road ahead of the evening rush hour in central Beijing, December 23, 2010. Beijing will limit issuance of new car plates to 240,000](https://c8.alamy.com/comp/2CNKADW/vehicles-are-seen-in-a-traffic-jam-on-jianguo-road-ahead-of-the-evening-rush-hour-in-central-beijing-december-23-2010-beijing-will-limit-issuance-of-new-car-plates-to-240000-annually-from-january-1-2011-in-an-effort-to-ease-the-capital-citys-traffic-jams-xinhua-news-agency-reported-reutersjason-lee-china-tags-environment-transport-2CNKADW.jpg)
Vehicles are seen in a traffic jam on Jianguo Road ahead of the evening rush hour in central Beijing, December 23, 2010. Beijing will limit issuance of new car plates to 240,000
![A traffic policeman on duty directs a vehicle to the side on 2nd Ring Road during rush hour in Beijing June 20, 2008. Beijing will introduce odd-even traffic restrictions for two months A traffic policeman on duty directs a vehicle to the side on 2nd Ring Road during rush hour in Beijing June 20, 2008. Beijing will introduce odd-even traffic restrictions for two months](https://c8.alamy.com/comp/2D24X2B/a-traffic-policeman-on-duty-directs-a-vehicle-to-the-side-on-2nd-ring-road-during-rush-hour-in-beijing-june-20-2008-beijing-will-introduce-odd-even-traffic-restrictions-for-two-months-from-july-20-to-help-ease-congestion-and-reduce-pollution-during-the-olympics-and-paralympics-the-city-government-said-reutersjason-lee-china-2D24X2B.jpg)