Small road capacity is the main cause of the traffic jam. When a volume of traffic or modal split generates demand for space greater than the available road capacity, traffic congestion occurs. So, too many vehicles, too old or narrow roads, and any other immature road infrastructure will lead to traffic jam. For example, in Sao Paulo City, Brazil, almost 1000 new cars are bought every day, while the capacity of public transport is quite limited: subway has only 38 miles of lines, and many roads are old and in bad condition. As a result, citizens spend 3 to 4 hours behind the wheel every day, making Sao Paulo the city with worst traffic jam in the world.

Traffic accident is another problem leads to traffic jam. Some of them are caused by road works and weather events, but for most of the time, this situation attributes to lax traffic rules and people’s disregard of them.

Though there are some problems leading to traffic jam, they can be solved by some actions. Solutions to small road capacity should be the improvement of road condition. More and wider roads, even underground railways and tunnels should be laid down to relieve traffic congestion. At the same time, better public transportation systems are also needed, including bus, MRT, LRT and many others. To reduce traffic accidents, stricter traffic laws and regulations should be issued. Governments should also raise the public awareness of traffic rules through education.

Solutions like using stricter laws and regulations can be easily applied, but the construction of better traffic facilities and public transportation needs big financial support. In addition, public education also needs time to put into practice. So in a short time, we still cannot solve this problem very