Traffic demand fluctuates both across days within the week and across months of the year. Daily and weekly fluctuations can be caused by work schedules, typical working business hours, and other factors. Monthly fluctuations can be caused by seasonal activities, such as sporting events, recreational activities, and school session schedules. Traffic demand also fluctuates across the year due to holidays, religious festivals, fairs, concerts, and other special events.

The base freeway analysis scenario accounts for traffic demand variation for different hours of a given day. To account for day-to-day traffic demand variability in the generation of multiple scenarios, the traffic demands for the analysis period are calibrated by applying a demand multiplier based on the day of week and month combination. The demand multiplier is a ratio of the day-month combination daily facility demand to the daily facility demand for a reference period. These factors are first used to adjust demand data used in the base scenario to what may be expected in terms of demand for the reference period. A second adjustment changes the demand of the reference day-and-month combination to the expected demand for any other day-month combination analyzed as part of the RRP.

Table 15-2

and

Table 15-3

provide default demand ratios for urban and rural freeways, respectively, with ratios shown relative to traffic demand on a Monday in January. These values can be supplemented by locally collected demand factors if they are available.