Depends. Statistics differ by country.
Generally, the answer is drink driving, because most mental functions are impaired or slowed down. But, again, it depends on country, since different countries have different statistics and laws (ie - It's illegal to drink alcohol completely in the United Arab Emirates).
Commonly human error, either made by the driver or by the signal operators. Also accidents caused by mechanical failure, track failure, signal failure, anything unwanted falling on the line...
The most common causes of accidents involving vehicles and pedestrians are distracted driving, failure to yield the right of way, speeding, impaired driving, and poor visibility.
Common causes of intersection car accidents include running red lights, failure to yield, distracted driving, speeding, and impaired driving. These accidents can be prevented by obeying traffic signals, yielding the right of way, staying focused on the road, driving at a safe speed, and never driving under the influence of alcohol or drugs.
Common causes of air accidents are weather and mechanical failure. Pilot error is also a cause of air accidents. There are cases where a combination of factors such as pilot error and mechanical failure take place causing an accident.
Equipment failure or human error.
Common causes of two cars crashing into each other on the road include distracted driving, speeding, reckless driving, failure to yield, running red lights or stop signs, and driving under the influence of alcohol or drugs. Other factors such as poor weather conditions, road hazards, and mechanical failures can also contribute to car accidents.
The main causes of drunk driving accidents are alcohol impairment, poor decision-making, and reduced coordination and reaction time.
Common causes of car vs pedestrian accidents include distracted driving, speeding, failure to yield, and poor visibility. These accidents can be prevented by staying alert while driving, obeying speed limits, yielding to pedestrians at crosswalks, and ensuring good visibility by keeping windshields clean and using headlights in low light conditions.
Common causes of teen accidents are their lack of maturity or experience, speeding, and/or drinking and driving.
There are many causes of bus accidents. One of the major causes of bus accidents, as with any auto accident, is the failure of a driver to see another driver on the road.
Some of the main causes of road accidents include over speeding and distractions from texting while driving or doing other things while driving. Unroadworthy vehicles and bad weather are also common causes.
A lot of the common causes for truck accidents involve the driver. The most common causes of truck accidents are, speeding, substance abuse, fatigued driving, improper inspection/maintenance and loading the trailer improperly.