An earlier FHWA study developed a design consistency evaluation procedure that used a
speed-profile model based on horizontal alinement.(7) The objective of this study, “Design
Consistency Evaluation Module for the Interactive Highway Safety Design Model (IHSDM),”
was to expand the research conducted under the previous FHWA study into two directions.
These directions were to (1) expand the speed profile model and (2) investigate three promising
design consistency rating methods. The expansion of the speed profile model is documented
elsewhere.(8) While operating speed is the more common method for evaluating the consistency
of a roadway, other methods have been discussed and explored. The three methods selected for
additional investigation in this study and documented in this report include: