After a preferred alternative has been selected and the project description agreed upon as stated in the environmental document, a project can move into the final design stage. The product of this stage is a complete set of plans, specifications, and estimates of required quantities of materials ready for the solicitation of construction bids and subsequent construction. Depending on the scale and complexity of the project, the final design process may take from a few months to several years.

FINAL DESIGN

After a preferred alternative has been selected and the project description agreed upon as stated in the environmental document, a project can move into the final design stage. The product of this stage is a complete set of plans, specifications, and estimates (PS&Es) of required quantities of materials ready for the solicitation of construction bids and subsequent construction. Depending on the scale and complexity of the project, the final design process may take from a few months to several years. The need to employ imagination, ingenuity, and flexibility comes into play at this stage, within the general parameters established during planning and project development. Designers need to be aware of design-related commitments made during project planning and project development, as well as proposed mitigation. They also need to be cognizant of the ability to make minor changes to the original concept developed during the planning phase that can result in a "better" final product. The interests and involvement of affected stakeholders are critical to making design decisions during this phase, as well. Many of the same techniques employed during earlier phases of the project development process to facilitate public participation can also be used during the design phase. The following paragraphs discuss some important considerations of design, including:

• Developing a concept

• Considering scale and

• Detailing the design.

Developing a Concept

A design concept gives the project a focus and helps to move it toward a specific direction. There are many elements in a highway, and each involves a number of separate but interrelated design decisions. Integrating all these elements to achieve a common goal or concept helps the designer in making design decisions. Some of the many elements of highway design are illustrated in Figure 1.5, including:

(a) Number and width of travel lanes, median type and width, and shoulders

(b) Traffic barriers

(c) Overpasses/bridges

(d) Horizontal-and vertical alinement, and affiliated landscape.