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From page 233... ... 233 Objective This example problem illustrates the following process: 1. Calculating reliability statistics for a freeway facility using the minimum required data for the analysis; 2. Read the entire page →
From page 234... ... 234 3. Estimating the demand variability profile; 4. Read the entire page →
From page 235... ... 235 • Diagnose the primary causes of the reliability problems on the facility so that an improvement program can be developed for the facility. Determining the Reliability Analysis Box The reliability reporting period has three dimensions: (1) Read the entire page →
From page 236... ... 236 measures consistently across different reliability analyses, allowing agency staff and stakeholders to begin developing an understanding of these metrics. In this example, the agency could pick the mean travel time index (TTI) Read the entire page →
From page 237... ... 237 Section A Section B Section C Figure I.3. Geometry of facility study section. Read the entire page →
From page 238... ... 238 Table I.3. Demand Ratios for I-40 Case Study (ADT for Mondays in January) Read the entire page →
From page 239... ... 239 Table I.4. Consolidated Demand Ratios for I-40 Case Study Season Monday– Wednesday Thursday Friday Average Winter 0.9969 1.0202 1.0765 1.0398 Spring 1.0813 1.1435 1.1989 1.0443 Summer 1.0689 1.1264 1.1767 1.0916 Fall 1.0267 1.0878 1.1281 1.1272 Average 1.0435 1.0945 1.1450 1.0744 Table I.5. Read the entire page →
From page 240... ... 240 Entries are minutes of identified weather type divided by total minutes of weekday study periods (in this example, weekdays, 6-h p.m. peak) Read the entire page →
From page 241... ... 241 The resulting estimated average percentage time with incidents present on the facility is shown in Table I.9. Results that are specific to individual demand patterns are too numerous to show here. Read the entire page →
From page 242... ... 242 PT(d) = percentage time of demand pattern d within the reliability reporting period; PT(w\|d) Read the entire page →
From page 243... ... 243 starting at the beginning of the study period, in the middle segment, and for an average duration will have a 4.00645%/ 18 = 0.22258% probability of occurrence. The starting time and duration must also be specified for the severe-weather scenarios (e.g., rain, snow) Read the entire page →
From page 244... ... 244 Step 7. Applying the HCM2010 Freeway Facility Analysis Method The HCM2010 freeway facility analysis method was applied to each of the 2,058 scenarios with capacity and speed–flow curve adjustments appropriate for each scenario. Read the entire page →
From page 245... ... 245 that all vehicle delays for these demand-only scenarios are accounted for within the facility or its entry links and ramps. The number of vehicles queued on the facility (and its entry links and ramps) Read the entire page →
From page 246... ... 246 Table I.15. Number of Scenarios, Runtime, and Coverage of Feasible Scenarios Inclusion Threshold No. Read the entire page →
From page 247... ... 247 Table I.17. Evaluation of TTI and PTI Results for I-40 Statistic I-40 Reliability Agency Threshold of Acceptability Conclusion Mean TTI 1.97 <1.93 Marginally unsatisfactory PTI 5.34 <3.55 Unsatisfactory Table I.18. Read the entire page →

From page 233...

... 233 Objective This example problem illustrates the following process: 1. Calculating reliability statistics for a freeway facility using the minimum required data for the analysis; 2.