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UBC Theses and Dissertations

Quantifying the relationship between geometric design consistency and road safety Ng, Joanne Cheuk Wai


Geometric design consistency is emerging as an important rule in highway design. Identifying and treating any inconsistency on a highway can significantly improve its safety performance. Considerable research has been undertaken to explore this concept, including identifying potential consistency measures and developing models to estimate them. However, little work has been carried out to quantify the safety benefits of geometric design consistency. The objectives of this study are to investigate and quantify the relationship between design consistency and road safety. A comprehensive collision and geometric design database of two-lane rural highways has been used to investigate the effect of several design consistency measures on road safety. Several collision prediction models which incorporate design consistency measures have been developed. The generalized linear regression approach has been used for model development. The models can be used as a quantitative tool to evaluate the impact of design consistency on road safety. An application is presented where the effectiveness of collision prediction models which incorporate design consistency measures is compared with those which rely on geometric design characteristics. It has been found that models which explicitly consider design consistency can identify the inconsistencies more effectively and reflect the resulting impacts on safety more accurately than those which do not. Finally, a systematic approach to identify geometrically inconsistent locations using the safety-consistency factor has been proposed.

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