AUTOMATION OF DETERMINING PASSING AND NO-PASSING ZONES ON 2-LANE HIGHWAYS

Establishing passing and no-passing zones has been a major task for hi ghway agencies to ensure that neither safety nor highway capacity is c ompromised. Currently, no-passing zones are established using a graphi cal technique, based on two-dimensional (2-D) horizontal and vertical alignments, and (or) field measurements. As a result, this task has be en time consuming, expensive, and subject to human errors. Moreover, d ecisions are taken by the field crew, and designers do not have flexib ility to change the alignment and check the corresponding effect on pa ssing zones. This article reviews analytical models developed by the a uthors for sight distance analysis an 2-D and 3-D highway alignments. Based on these models, two computer programs, MARKS and MARKC, are dev eloped to determine the sight distance on 2-D separate and 3-D combine d alignments, respectively. MARKS was verified graphically, and MARKC was verified using field measurements. The verification showed that th e two programs can determine the available sight distance accurately. The implementation of the developed software has the potential benefit s of eliminating human errors, saving time and cost, providing greater flexibility to designers to change the alignment and easily check the effect on passing zones, and transferring the decision of allowing or disallowing passing from field crews to engineers.