Did Tractor-Trailer Turn from the Proper Lane?


Steven M. Schorr, PE ::::

Case Synopsis: A tractor-trailer executed a right turn.  The tractor-trailer operator testified that he was in the right lane, and moved only a few feet into the left lane before he turned [to allow his trailer to make the turn].  As he executed the right turn, a car tried to pass him on the right and a collision occurred as the car and tractor entered the intersection.

Expert Analysis: The car operator testified that he was approaching the intersection when the tractor-trailer suddenly turned right from the left lane resulting in the collision.  Specifications of the tractor-trailer were utilized to reconstruct the specific path the tractor-trailer had to take to end up in the point of rest position as defined by the scene data.  The analysis showed that “both” operators were partially correct.  In order for the tractor-trailer to end up in its point of rest position as defined by the data, the tractor-trailer had to have turned from a position mostly in the left lane.  However, the analysis also showed that the tractor-trailer had to have started its turn from the right lane and that the car did try and “squeeze” by as the tractor-trailer moved left prior to moving to the right. 

Conclusion: It is important to note that the tractor-trailer operator’s turn, while not completely from the left lane, was not consistent with the Commercial Driver’s Manual.  Specifically, the CDL Manual establishes that when the tractor-trailer operator moves the tractor to the left [prior to turning right] he/she should keep the trailer in the right lane.  By doing so, the tractor-trailer compensates for the off-tracking trailer unit, while blocking the right lane, thus preventing the type of collision that occurred in this case.

Categories: Case Studies


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