APPLICATION FOR AUTOMATED-DETERMINATION OF PASSING AND NO-PASSING ZONES - A CASE-STUDY

Currently, passing and no-passing zones are established using a graphi cal technique and (or) field measurements. As an alternative, this art icle presents an application of two computer programs, MARKS and MARKC , developed by the authors to establish the marking of passing and no- passing zones on two-dimensional (2-D) separate and three- dimensional (3-D) combined highway alignments, respectively. Using a 7 km segment on Highway 61, a four-phase study is conducted to show the applicabil ity of the programs, to compare the 2-D and 3-D sight distances, to de termine the marking of passing and no-passing zones according to curre nt standards, and to determine the marking according to a revised pass ing sight distance (PSD) model developed by the authors. The programs are shown to be accurate and applicable to real highways, and use the data that are already available in the highway agencies. A significant difference between the 2-D and 3-D sight distances is shown to exist, and therefore sight distance should be determined in 3-D combined ali gnments rather than 2-D separate alignments. A considerable difference is also shown between the markings according to current standards and according to the revised PSD model. It is concluded that the implemen tation of the developed software has the potential benefits of elimina ting human errors, saving time and cost, providing greater flexibility to designers to change the alignment and easily check the effect on p assing zones, and transferring the decision of allowing or disallowing passing on special circumstances From field crews to engineers. Also, revisions of the current marking standards are recommended.