Alberta Guidelines for Upgrading Bridgerails and Approach Guardrail Transitions

Experimental crash testing has demonstrated that static design procedures are inadequate to predict the complex interaction that occurs when an errant vehicle strikes a bridgerail system. As a result of this deficiency, bridgerail systems designed to old standards do not provide the optimum protection to the occupants of the vehicle in terms of personal safety, or of helping to ensure that the driver of the vehicle is able to maintain control after impact. Following the publication and adoption of the Canadian Highway Bridge Design Code (CAN/CSA-S6-00) by Alberta Transportation (AT), a series of standard drawings incorporating the new safety concepts were developed by AT for use on new construction projects. It was also decided that in addition to applying the improved standards for new construction, it would be prudent to apply the same safety concepts to the upgrading of existing bridgerail systems whenever practical. However, since it is not practical to crash test existing installations, and that there are limitations on the amount of funding available in the construction program for rehabilitation, it was recognized that guidelines on ‘when and how to rehabilitate’ would need to be developed. It was also recognized that in addition to engineering issues, the Guidelines would have to include features that would enable priorities for rehabilitation to be established, and from these priorities a program for upgrading the existing rail systems could be developed, as and when funds became available. This paper will give an overview of the development of the Guidelines, and the discussion will include the evaluation of existing AT bridgerail systems and approach guardrail transitions, and the needs to upgrade with respect to safety. The paper will also discuss prioritizing projects using cost-benefit analysis, based on encroachment rates, severity indices, present value costs, etc. The Guidelines are a joint effort between Alberta Transportation and UMA Engineering Ltd.