Multi car accidents are almost always caused by another vehicle who tries to  swerve away from the  original accident scene. As other vehicles try to avoid the original accident, they may  swerve on to other lanes, which have other vehicles. The secondary impact is considered to be more dangerous than the original impact since other vehicles may be traveling at very high speeds.

Examples of reasons why multi-car accidents occur include:

• Poor road conditions: when roads have potholes or are not paved properly, cars may swerve to other lanes to avoid driving onto jagged areas. When this occurs, the likelihood of being involved in an accident increases. Other cars who drive onto jagged roads could have their tires popped which could result in a rear end collision.
  
  
• Poor weather conditions: California is lucky enough to experience several days of hot sun. But, excessive rain could cause cars to slip on roads.
  
  
• Driving while distracted: texting and driving is the number one cause of distracted driving in California. As drivers take their eyes off the road for one second to check on a text, a severe accident may result.
  
  
• Drowsy driving: many drivers, including truck drivers, choose to get behind the wheel after driving several hours in a day. This could cause the driver to fall asleep behind the wheel, and rear end other vehicles. 
  
  
• Speeding while driving: speeding will not give a driver enough time to come to a complete stop, especially if there is abrupt traffic and all the cars are stopped. This results in rear-end collisions. 
  
  
• Failing to stop at a stoplight: when a driver drives through a red light, they could cause rear-end collisions, as a result other cars may swerve out of the way and sideswipe other vehicles.