QA/QC in Transport Infrastructures: Issues and Perspectives

Abstract

Transport infrastructures (road and highway networks, railways, terminal facilities, airports, mass transit systems, bicycle paths and pedestrian walkways, etc.) have significant impacts on the development of regional and national economies. However, the effectiveness of these impacts over the time has to be established based on the actual quality of all the pertaining components of the infrastructure asset (pavement, safety barriers, signals, illumination, embankment, drainage, etc.). Quality can be interpreted as the degree of excellence of a product or service, or as the degree to which a product or service satisfies the needs of a specific customer or, finally, as the degree to which a product or service conforms with a given requirement. In more detail, quality assurance (QA) refers to all those planned and systematic actions necessary to provide confidence that a product or facility will perform satisfactorily in service. At the same time, quality control (QC), also called process control, relates to those QA actions and considerations necessary to assess and adjust production and construction processes so as to control the level of quality being produced in the end product (Fig.1). Note that QA (which includes QC) is an infrastructure (e.g. highway) agency responsibility and involves all the process (planning, design, plan and specifications, construction, etc.), while QC is a producer–contractor responsibility which mainly affects construction. Furthermore, QC is not simply QA in construction, due to the fact that both independent assurance and acceptance procedures refer to QA in construction but they are NOT a part of QC. The entire QA/QC process includes: i) setting up the initial data collection or experimentation to determine typical parameters of current construction; ii) designing the acceptance plan itself, including selecting quality characteristics (and corresponding specification limits), statistical quality measure (and corresponding quality levels), buyer’s and seller’s risks, lot size, number of samples (sample size), specification and/or acceptance limits, and payment–adjustment provisions. As is well known (Burati et al, 2003), traditionally, highway specifications spelled out in detail the work that was to be done by the contractor under the form of materials and methods specifications (also called method specifications, recipe specifications, or prescriptive specifications). In this case, specifications direct the contractor to use specified materials in definite proportions and specific types of equipment and methods to place the material. On the contrary, end result specifications require the contractor to take the entire responsibility for supplying a product or an item of construction.