Traffic accident is one of the main problems that kill hundreds of people in Cambodia every year. Many people die every day and this is the big concern for the government because they have to spend much money to solve this problem. According to my research and some document that I have read on the internet and other books I found that there are for factor that led traffic accident and now I will tell you in detail about each factor.Human : The main problem is human error which is one amount other factor that killed a lot of people than other factors. The human error consists of small factor include: Drunk driver is one of the main problems that usually kill a lot of people not only in the city but also countryside. After drinking win people usually drive their vehicle or car and sometime they cannot control their vehicle or car at all and frequently cause accident. Sometime it is not only affect to the person who causes accident but also affect to people who is riding with them and other people that is driving on the road too.Another problem is that when they drive their motor on the road they do not wear helmet.After traffic law in Cambodian is approve we can see that most people they usually wear helmet when they travel on the road but some of them that still not follow the traffic law. They obey the law only when they met with traffic police near the traffic light.They just put their helmet in front of their motor and they wear it when they met the traffic police. This problem usually happen to teenagers who usually thing that it is not so handsome or they feel like something on their head when they wear it sometime it makes them fell not so attractive for the other teenagers. Human error is responsible for more than 98% of casualties1. Human errors: fast speed, alcohol abuse, not respect right of way, dangerous overtaking, changing lane without due care, driving against flow of traffic, fatigue or illness, not respect traffic light and signs, wrong use of high beams, or improper use of mobile phones.More than 50% of fatalities were due to speeding while another 18% were caused by alcohol abuse. Crashes resulting from not respecting the right of way and dangerous overtaking occurred more during the daytime than nigh time, but crashes involving alcohol abuse were more of a problem during the night time than daytime. Road and weather conditions are responsible for less than 10% of casualties, while vehicle defect is responsible for only 5% of casualties. Other elements of the cause are lack of traffic law knowledge, no respect for the law.Fast driving is another factor that cause by human factor. As we can see in Cambodia today even the law has limit the speed for all drivers but some drivers still violate it. Sometime when they drive in the crowded place such as market or some other busy road in provincial town and in the city they do not slow down at all and they do not care about other people that was selling and walking on the road. In the city we usually see teenagers that drive modern car or motor on the road. They usually drive over speed limitation. Moreover, dangerous over taking is usually cause by human themselves.