Transportation planning and design decisions are typically made using point estimates of traffic and safety measures. This report addresses the uncertainty of data used to make these decisions. It focuses on two data elements — project safety ratings and volume estimates from traffic counts. For safety ratings, the Kentucky Transportation Cabinet’s Strategic Highway Investment Formula for Tomorrow (SHIFT) crash history score is used as a case study. Confidence intervals are developed for the Cabinet’s new safety metric, which incorporates estimates of future crashes by severity as well as excess expected crashes above safety goals. For traffic counts, the report develops confidence intervals based on daily and monthly expansion factors across multiple permanent count recording stations. Results should help users of these data better understand the range of data the point estimates represent and the likelihood that projects based on these plans and designs will function as expected.

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