Selecting a Design Method
Selection of a design method will usually depend on three factors:
- Construction practice and material specifications. For instance it would not usually be practicable to choose an American design method, linked to American specifications and standards, in the UK; when British design methods are closely linked to British construction practice, specifications and standards.
- The pavement condition expected at the end of the design life (known as the failure criterion), which governs likely maintenance requirements. In areas where low downtime for maintenance is vital a design method with a combination of a conservative failure criterion and a high design reliability (the probability of the pavement life equalling or exceeding the design life) may be appropriate. However, the pavement thickness and capital cost will be higher, and in most circumstances a less onerous design method will be suitable.
- Whether an evaluation of an existing pavement and rehabilitation/overlay design is required. The failure criterion is usually defined by the proportion of the pavement area that has failed structurally at the end of the design life, e.g. “structural cracking of 30% to 50% of bays in the trafficked areas”.