Guiderail or Not?



Walter M. Wysowaty, PE, CME, MBA, Municipal / Civil Engineer ::::
Case Synopsis: The plaintiff was traveling southbound in the right lane when another vehicle, while changing lanes, collided with her, causing the plaintiff to lose control of her vehicle and drive off of the roadway where her vehicle then struck a tree. The plaintiff alleged that the State of New Jersey should have provided a guiderail at this location due to the presence and location of the tree which, they alleged, presented an obstruction within the clear zone of the roadway.

Expert Analysis: An inspection and subsequent analysis was conducted. The subject tree was located 35.2-feet from the edge of travel way (shoulder line in this case). The slope between the edge of the travel way and the subject tree was a fill slope with a maximum cross slope of 12.4% (8:1). The NJDOT Roadway Design Manual and the AASHTO Roadside Design Guide provide parameters for the need and placement of guiderails based on the design speed of the roadway, the traffic volume along the roadway, and the slope of the border adjacent to the roadway. According to NJDOT and AASHTO, a roadway with a design speed of 70mph. (Route I-295 design speed is 70 m.p.h.), an A.D.T. of over 6,000 (Route 295 A.D.T. is 90,000), and a fill slope of 6:1 or flatter (the fill slope along Route I-295 is 8:1 which is flatter than 6:1) requires a clear zone distance of 30-34 feet.
The subject tree that the plaintiff encountered, based on a survey ordered by the plaintiff and based on observations made during the site inspections, is located outside the required clear zone of 30 feet. Therefore, the State of New Jersey was not required to provide guiderail at the location where the accident occurred.
Case Result: Case settled.
Walter M. Wysowaty, P.E., CME, MBA is a Municipal / Civil Engineer with DJS Associates and can be reached via email at or by phone at 215-659-2010.

Categories: Automotive / Mechanical Engineer | Collision / Accident Reconstruction

Tags: Collision / Accident Reconstruction | Walter M. Wysowaty


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