The subject of design exceptions at the project level inevitably generates controversy. CSS skeptics have argued that accepting the premise of CSS inevitably means that more design exceptions will occur, or that they will be expected to more readily accept a design exception under pressure from a stakeholder or interest group. A commitment to CSS by an agency does not mean abandonment of design standards. Professional engineers are ethically and legally required to follow the accepted practices of the profession. A design exception is a documented decision to design a highway element or segment of highway to a design criterion or value that does not meet the minimum value that has been established for that highway or project. Examples may include the use of a narrower shoulder than design standards show, a curve with radius smaller than the minimum for the selected design speed, or a crest vertical curve that does not provide the minimum stopping sight distance for the selected design speed. FHWA has designated 13 controlling criteria as being of sufficient importance to warrant a formal design exception, summarized below.

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Design Exceptions - CSS Quick Facts