For discussion of MOEs see

Section 15.3.2

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Chapter 11 of the HCM 7th Edition builds on the basic freeway analysis presented in the HCM and provides a methodology for evaluating a freeway’s travel time reliability over a multiday or multi-month reliability reporting period (RRP) and under a variety of conditions, such as lane closures, traffic incidents, or periods of inclement weather.

Freeway reliability refers to the distribution or variability of travel times of trips through an entire freeway facility over a period of time, typically one year. Travel time variation may be caused by recurring variations in demand by hour of day, day of week, and month of year, which are generally predictable in distribution. Travel time variation may also be caused by less predictable non-recurring variations in demand or available roadway capacity.

The methodology estimates the impacts of recurring and nonrecurring congestion on travel time variability and can also estimate the impacts that TSMO and TDM strategies have on travel time and travel time variability. Many TSMO and TDM strategies target reducing congestion and delays associated with the nonrecurring factors described below and, as a result, reducing travel time variation. Nonrecurring factors that impact travel time include:

HCM freeway reliability analysis methods may be used to assess the influence of TSMO and Active Transportation and Demand Management (ATDM) projects on a freeway and the impacts of recurring and nonrecurring events that occur on the facility. The reliability analysis allows individual TSMO and ATDM projects, as well as any combination of projects, to be analyzed under a variety of freeway conditions. The analysis determines the full range of capacity under any condition, combination of conditions, and implemented transportation improvements.

For additional information and case studies on TSMO, ATDM, and performance measurement see

Appendix P, Section 2 – External References (References 5,6, and 7)

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