It's every parent's nightmare: a road trip to a band competition or football game ends in tragedy when the school bus or van is involved in an accident. It happened recently in Texas when an Abilene Christian University bus ran off the road and flipped over, killing one student and leaving four in critical condition.

The driver of the bus, a faculty member at ACU, apparently lost control of the bus on a curve and left the roadway, hitting a culvert that caused the bus to overturn. Texas State Police are conducting an investigation, saying that it may be months before anyone is charged in the crash. Trooper Phillip Dean noted that it is often difficult to assign fault or liability in one-vehicle accidents such as these.

These types of accidents can be attributed to many things, although the police are waiting for the results of the investigation before commenting on the specifics of this accident. Possibilities include distracted driving, problems with the vehicle because of poor maintenance or manufacturing defects, road design and repair issues, drug or alcohol use, training issues and a host of other possible causes. The state police will be conducting a computerized reconstruction of the accident in an effort to determine what really happened.

A single vehicle crash can be more challenging to investigate because the sequence of events may not be clear. In a two-car crash, it is relatively easy to determine that one vehicle ran a stop sign or made an illegal turn. Identifying the reasons for losing control can be much more subjective, and in some instances can never be determined.

The bus was transporting students and faculty to Medina for their annual visit to a children's home where they volunteer each year.

Source: ABCnews.com, "Texas Troopers Interviewing Bus Crash Survivors", by Betsy Blaney, Nov. 5, 2011.