Distribution of uniform reliability over AADTs estimated for a new highway route

Abstract

AADT estimation for a new highway route has been performed depending on complicated procedures with diversified variables. However, regardless of types of estimation procedures and variables, errors between AADTs estimated and observed appear in most AADT estimation. They have been statistically expressed in terms of forecast error in percent (FEIP). The presented study is based on FEIP collection at freeway sections. It is found that by the province, there exist historical patterns of FEIPs, safety margins, and reliabilities of estimation. Based on this finding, this paper provides a way to distribute a uniform reliability of AADT estimation for a new highway route. Uniform reliability distribution over AADTs estimated in serial sections of a highway route is important because a uniform reliability of AADTs at the design level potentially guarantees to sustain a uniform level of service during the operation of a highway in serial sections of a highway route. Through the example study in the paper, it may be concluded that the introduction of the reliability concept and historical patterns of FEIPs may improve the AADT estimation in design of a new highway route over which overestimation or underestimation have prevailed.