Typical traffic forecasts include the project opening year, the design year (i.e., opening year + 20 years), and the pavement design year (i.e., opening year + 30 years). Traffic forecasts may also include an interim year. An interim year occurs between the opening year and pavement design year. Interim years may be used if the proposed improvements show failing Level of Service (LOS) prior to the design year. The opening year is the first year in which the proposed improvements are expected to be open to traffic. If the project is proposed to be implemented in phases, the opening year is the year the first phase will be opened to traffic. Opening year is typically determined by project size, complexity, and schedule, with respect to the letting date. The let date is dependent on the planning and programming of projects.