Development of Guardail Runout Length Calculation Procedures
REPORT NUMBER
TRP-03-057-96
AUTHORS
Dean Sicking, Daniel Wolford
PUBLICATION DATE
1996-05-01
ABSTRACT
Guardrail runout length recommendations contained in AASHTO's Roadside Design Guide were reevaluated in order to determine optimal guardrail length of need. Encroachment data collected along
Canadian highways (4) was evaluated in a manner similar to that used with Hutchinson and Kennedy
encroachment data (3) to reproduce procedures contained in AASHTO's Roadside Design Guide. A
benefit cost analysis of extending guardrails was also conducted as an alternative procedure for defining
appropriate guardrail runout lengths. Both analysis procedures indicate that guardrail runout lengths
recommended by the Roadside Design Guide are excessive. Highway agencies are recommended to
select one of the two new procedures for identifying appropriate guardrail runout lengths. Guardrail runout
length recommendations contained in AASHTO's Roadside Design Guide were re-evaluated in order to
determine optimal guardrail length of need. Encroachment data collected along Canadian highways (4)
was evaluated in a manner similar to that used with Hutchinson and Kennedy encroachment data (3) to
reproduce procedures contained in AASHTO's Roadside Design Guide. A benefit cost analysis of
extending guardrails was also conducted as an alternative procedure for defining appropriate guardrail
runout lengths. Both analysis procedures indicate that guardrail runout lengths recommended by the
RoadsideDesignGuide are excessive. Highway agencies are recommended to select one of the two new
procedures for identifying appropriate guardrail runout lengths.
KEYWORDS
Guardrail, Benefit/Cost Analysis, Benefit, Cost, Analysis, Runout Length, Length of Need, Runout Lengths