Incorporating Travel Time Reliability into the Highway Capacity Manual (2014) / Chapter Skim
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Pages 142-168
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142 This appendix provides guidance for the use of the Urban Streets Reliability Engine (USRE) , referred to as STREETVAL in the proposed Highway Capacity Manual (HCM)
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143 • Special events; • Traffic control devices; • Weather; and • Inadequate base capacity. These sources can result in the formation of oversaturated operation for extended time periods.
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144 HCM Data Set An HCM data set comprises the input data needed to evaluate an urban street facility using the HCM methodology. These data are also needed for the reliability methodology.
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145 • Calib-Weather: calibration factors and default data for weather; • Calib-Demand: calibration factors and default data for demand volume; • Calib-Incident: calibration factors and default data for incidents; and • Analysis: statistical analysis of results from multiple runs. The Set Up, Facility Evaluation, and Performance Summary worksheets will be used for every evaluation in the order listed.
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146 before the button is clicked. A numeric counter is shown after the button is clicked.
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147 Each data set is saved in a file using a file name with a .txt extension. The file name includes the text of the file name associated with the base (or alternative)
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148 average conditions for the analysis period during that month. Work zones that exist at the same time as a special event must be described using one alternative data set.
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149 appropriate traffic volume adjustment factors for each scenario. The functional classes that are considered are identified in the following list: • Urban expressway; • Urban principal arterial street; and • Urban minor arterial street.
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150 the intersection lane assignments and signal timing plan should be the same during the study period. If the facility has two or more time-of-day signal timing plans, then a separate study period should be established for each plan period.
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151 worksheets can also be changed if appropriate local data are available. Guidance for using the USCE to create an HCM data set is provided in the section titled "Urban Streets Computational Engine Data Entry." The analyst should confirm that he or she has enabled macro operation in the workbook before starting the data entry process.
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152 analysis period is selected, then additional input data are needed in the Supplemental Input Data section (discussed later in this section)
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153 number data entry cell is used for weather predictions, another for demand prediction, and a third for incident prediction. A unique sequence of events is predicted for a given seed number.
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154 Alternatively, the analyst can chose to evaluate every scenario for every other day (i.e., enter 2)
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155 Results Review and Interpretation This section describes the output data provided by the tool. These data are provided in the following four worksheets: • Performance Summary; • Weather; • Demand; and • Incident.
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156 shown in Figure B.11 so that the figure text could be kept at a readable size. The second location for output data, just below the weather statistics, lists in chronological order the predicted weather conditions for each analysis period.
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157 The Incident worksheet lists in chronological order the incident type and location for each analysis period. One group of 12 columns is dedicated to each intersection and to each segment on the facility.
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158 in the Highway Safety Manual (American Association of State Highway and Transportation Officials 2010)
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159 • Segment 6: input data describing the segment located between Intersections 6 and 7; • Segment 7: input data describing the segment located between Intersections 7 and 8; and • Segment 8: input data describing the segment located between Intersections 8 and 9. The segment and intersection numbers are defined sequentially in the EB or NB direction of travel.
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160 parameters can be entered in the Supplemental Urban Street Parameters section that is located at the bottom of the Set Up worksheet (not shown)
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161 entry. This schematic is repeated at the top of the Intersection worksheet and at the top of each Segment worksheet.
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162 fwid = saturation flow rate adjustment factor for approach width; freduce = saturation flow rate adjustment factor for reducing lanes during work zone presence; aw = approach lane width during work zone (total width of all open left-turn, through, and right-turn lanes plus any setback distance to adjacent curb or work zone traffic control devices) , ft; no = number of left-turn and through lanes open during normal operation; and nwz = number of left-turn and through lanes open during work zone presence.
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163 not be discussed in this section. The remaining two sections are described in the following paragraphs.
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164 Software Description The software used for a reliability evaluation consists of two Excel workbooks and one executable file. These files are described in this section.
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165 The file name for this file is yyyymmdd-HHhh.out. The file naming convention is the same as that for the scenario data set file as described in the previous section.
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166 "FileName:","TexasAM2.out" "NbrSegments",2 "SEGMENT:",1 " 02 06" "SegLength",1800.............................................................................
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167 rename it to create a new workbook; one workbook should be created for each strategy being considered. Specifically, modify the workbook file name by attaching a suffix to indicate the specific strategy to which this workbook will apply (e.g., C17_A06-4_G06-4_V2010_ L08_s1.xls)
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168 results from each run will be saved in the appropriate replication folder. After each run, the appropriate replication folder should contain one scenario data set file and one scenario output file for each analysis period associated with that replication.
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Key Terms
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