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| Section | Limitations |
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"Urban Street Methodology" (chapter 15, HCM 2000) |
This methodology does not directly account for the following conditions that can occur between intersections:
Because any one of these conditions might have a significant impact on the speed of through traffic, the analyst should modify the methodology to incorporate the effects as well as possible. |
"Signalized Intersection Methodology" (chapter 16, HCM 2000) |
This methodology does not take into account the potential impact of downstream congestion on intersection operation, nor does it detect and adjust for the impact of turn-pocket overflows on through traffic and intersection operation. |
"Unsignalized Intersection Methodology" (chapter 17, HCM 2000) |
HCM 2000 does not include a detailed method for estimating delay for yield sign-controlled intersections. All of the methods are for steady-state conditions (i.e., the demand and capacity conditions are constant during the analysis period). The methods are not designed to evaluate how fast or how often the facility transitions from one demand/capacity state to another. Analysts interested in that kind of information should consider applying simulation models. |
"Pedestrian Methodology" (chapter 18, HCM 2000) |
HCM 2000 treats each of these
facilities from the point of view of the pedestrian. Procedures for
assessing the impact of pedestrians on vehicular capacity and LOS are
incorporated into other chapters. The material in HCM 2000 is the result of
research sponsored by FHWA. The pedestrian methodology for midblock sidewalk analysis cannot determine the effects of high volumes of pedestrians entering from the doorways of office buildings or subway stations. It also cannot determine the effects of high volumes of motor vehicles entering or leaving a parking garage and crossing the sidewalk area. Moreover, the methodology does not consider grades; it is adequate for grades from -3 to +3 percent; however, the effects of more extreme grades have not been well documented. |
"Bicycle Methodology" (chapter 19, HCM 2000) |
The bicycle methodology does not account for bicycle paths or lane-width reduction caused by fixed objects adjacent to these facilities. No credible data were found on fixed objects and their effects on bicycles using these types of facilities. In addition, the methodology does not account for the effects of right-turning motor vehicles crossing bicycle lanes at intersections or midblock locations, and grade is not considered. The methodology can be used for the analysis of facilities with grades from -3 to +3 percent. The effects created by more extreme grades are unknown. |
"Two-Lane Highway Methodology" (chapter 20, HCM 2000) |
Some two-lane highways-particularly
those that involve interactions among several passing or climbing lanes-are
too complex to be addressed by the procedures of HCM 2000. For analytical
problems beyond the scope of HCM 2000, see part V of HCM 2000, which
describes the application of simulation modeling to two-lane highway
analyses. Several design treatments discussed in appendix A in HCM 2000 are
not accounted for by the methodology. The operational analytical methodologies in HCM 2000 do not address two-lane highways with signalized intersections. Isolated signalized intersections on two-lane highways can be evaluated using the signalized intersections methodology (chapter 16, HCM 2000). Two-lane highways in urban and suburban areas with multiple signalized intersections at spacings of 3.2 km (2.0 mi) or less can be evaluated using the urban street methodology (chapter 15, HCM 2000). |
"Multilane Highway Methodology" (chapter 21, HCM 2000) |
The methodology in HCM 2000 does not take into account the following conditions:
|
"Freeway Methodology" (chapter 22, HCM 2000) |
A complete discussion of freeway
control systems or even the analysis of the performance alternatives is
beyond the scope of HCM 2000. The reader should consult the references
identified in HCM 2000. The methodology does not account for delays caused
by vehicles using alternate routes or vehicles leaving before or after the
duration of the study. Certain freeway traffic conditions cannot easily be analyzed by the methodology (e.g., multiple overlapping bottlenecks). Therefore, other tools may be more appropriate for specific applications beyond the capabilities of the methodology. Refer to part V, HCM 2000, for a discussion of simulations and other models. User demand responses, such as spatial, temporal, modal, or total demand responses caused by traffic management strategies, are not automatically incorporated within the methodology. After viewing the facility traffic performance results, the analyst can modify the demand input manually to analyze the effect of user demand responses or traffic growth. The accuracy of the results depends on the accuracy of the estimation of the users' demand responses. The freeway facility methodology is limited to the extent that it can accommodate demand in excess of capacity. The procedures address only local oversaturated flow situations, not systemwide oversaturated flow conditions. The completeness of the analysis will be limited if freeway segments in the first time interval, the last time interval, and the first freeway segment do not all have demand-to-capacity ratios less than 1.00. The rationale for these limitations is discussed in the section on demand-capacity ratio. Given enough time, the analyst can analyze a completely undersaturated time-space domain manually, although this is difficult. It is not expected that analysts will ever manually analyze a time-space domain that includes oversaturation. For heavily congested freeway facilities with interacting bottleneck queues, the analyst may wish to review part V, HCM 2000, before undertaking this methodology. |
"Basic Freeway Segment Methodology" (chapter 23, HCM 2000) |
The methodology does not apply to or take into account (without modification by the analyst) the following:
The analyst would have to draw upon other research information and develop special-purpose modifications of this methodology to incorporate the effects of the above conditions. |
"Freeway Weaving Methodology" (chapter 24, HCM 2000) |
The HCM 2000 methodology does not specifically address the following subjects (without modifications by the analyst):
The last subject, which has been treated in previous editions of HCM, has been deleted. Multiple weaving segments must be divided into appropriate merge, diverge, and simple weaving segments for analysis. |
"Ramp and Ramp Junction Methodologies" (chapter 25, HCM 2000) |
The HCM 2000 methodology does not take into account, nor is it applicable to (without modifications by the analyst), the following:
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Source: HCM 2000
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