You should only overtake, rather than undertake while driving. However, do not be surprised when other motorists break this rule. Speed limits vary throughout the city. Speed limits on the Second, Third and Fourth Ring Roads are 50 to 80kph. The limit on the Fifth Ring Road is 50 to 90kph. The limit on the Airport Expressway is 120kph. The limit on the Jingjingtang Expressway is 110kph. Limits are 70kph on main streets like Changan, Pingan and Qianmen. Special limits are posted in hazard zones and around schools.