Establishing Practical Approach for Design Consistency Evaluation

The concept of design consistency has lately been gaining greater acceptance in North America. Considerable research work is being carried out and steps have already been taken to incorporate this concept into the design practices in Canada and the United States. However, a standard procedure that can be followed by designers to evaluate the design consistency of new or existing alignments is still lacking. This paper compiles different measures for evaluating geometric design consistency, as presented in available research work, to identify their potential applicability and any required future research. These consistency measures are operating speed, vehicle stability, alignment indices, and driver workload. Four fictitious alignments were presented and subjected to these measures in a step-by-step exercise of consistency evaluation. A relationship between design consistency measures and safety, which is the main objective of the design consistency concept, is also discussed. Overall, consistency measures were successful in identifying inconsistencies in the proposed alignments. However, the exercise showed the need for more research work in a number of areas for complete and accurate consistency evaluation.

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