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Optimizing Design of Highway Horizontal Alignments: New Substantive Safety Approach
Author(s) -
Easa Said M.,
Mehmood Atif
Publication year - 2008
Publication title -
computer‐aided civil and infrastructure engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.773
H-Index - 82
eISSN - 1467-8667
pISSN - 1093-9687
DOI - 10.1111/j.1467-8667.2008.00560.x
Subject(s) - collision , tangent , geometric design , computer science , horizontal and vertical , spiral (railway) , simulation , engineering , geometry , mathematics , mechanical engineering , computer security
Highway agencies are continually facing safety problems on highways, especially on horizontal alignments. Traditionally, the geometric design implicitly considers safety through satisfying minimum design requirements for different geometric elements. This article presents a new substantive‐safety approach for the design of horizontal alignments based not only on minimum design guidelines, but also on actual collision experience. The curve radii, spiral lengths, lane width, shoulder width, and tangent lengths are determined to optimize the mean collision frequency along the highway. The model allows the parameters of the horizontal alignment to vary within specified ranges. The model also considers any specified physical obstructions in selecting the optimal alignment. Collision experience is addressed using existing collision prediction models for horizontal alignments and cross sections. The model is applicable to two‐lane rural highways for which collision prediction models exist. Application of the model is presented using numerical examples. The proposed substantive‐safety approach takes horizontal alignment design one step further beyond the minimum‐guideline concept, and therefore should be of interest to highway designers.