How the ATAC scored corridors: crash rates and economic cost explained

At the Aug. 18 meeting staff explained the RSA scoring metrics the committee used to compare corridors. Presenter Cat Proveni described the corridor crash-rate calculation: compute daily vehicle miles traveled per segment using average annual daily traffic (ADT) and segment length, convert to annual vehicle miles, sum crash counts over five years, and compute crashes per million vehicle miles traveled.

"And so our crash rate for this um example is 0.56 crashes per million vehicle miles traveled," Proveni said while walking members through a numeric example. She also described the CACO (average annual economic cost) approach, which multiplies counts of fatal, suspected serious-injury and other crash classes by FHWA- and AASHTO-based comprehensive-cost values and divides by the analysis period to produce an annualized economic cost estimate. Staff noted some cost inputs come from federal guidance and are updated periodically.

Members asked whether the economic-cost values vary year to year; staff replied that the group tries to cross-check Federal Highway Administration updates, and that the values can change across reporting cycles. Committee members requested corridor lengths and other scoping details to better understand how NMDOT may evaluate application complexity and cost.