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From page 119... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 107 APPENDIX F DECISION RULE DEVELOPMENT SLSG = LIMITED ACCESS Overview This section provides an overview of the decision rules selected for the SLSG of Limited Access. Read the entire page →
From page 120... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 108 Table 46. Overview of decision rules for SLSG = Limited Access. Read the entire page →
From page 121... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 109 and design speed of limited-access facilities (17, Table 8-1) Read the entire page →
From page 122... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 110  Average AADT (two-way total) for the study period. Read the entire page →
From page 123... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 111 Table 48. Average KABC crash rate per 100 MVM for Limited Access SLSG. Read the entire page →
From page 124... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 112 (both length and offset are required) is greater than desired for analysis of the posted speed limit. Read the entire page →
From page 125... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 113 Table 49. Minimum section length for a particular speed limit. Read the entire page →
From page 126... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 114 Variables Included in SLS-Tool Table 50 provides an overview of the variables along with the variable value that would trigger using either C85, RD85, or C50. Following the table is a justification for selecting those variables and break points. Read the entire page →
From page 127... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 115 Table 50. Overview of decision rules for SLSG = Undeveloped. Read the entire page →
From page 128... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 116 Figure 24. Crash prediction using HSM equations for four-lane undivided and divided roadways. Read the entire page →
From page 129... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 117 design criteria may be considered for local and minor collector roads and streets that carry 2,000 vehicles per day or less in accordance with the AASHTO Guidelines for Geometric Design of Very Low-Volume Local Roads. (17, page 52) Read the entire page →
From page 130... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 118 Crash Level USLIMITS2 can produce a suggested posted speed limit whether crash data are available or not (11) Read the entire page →
From page 131... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 119 Table 51. Average crash rate per 100 MVM for Undeveloped SLSG (i.e., context = rural with roadway types of principal arterial, minor arterial, collector, or local) Read the entire page →
From page 132... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 120 Table 52. Average F&I crash rate per 100 MVM for Undeveloped SLSG (i.e., context = rural with roadway types of principal arterial, minor arterial, collector, or local) Read the entire page →
From page 133... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 121 curvature to significantly affect crash occurrence. These data were reanalyzed for purposes of guideline development here. Read the entire page →
From page 134... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 122 Table 53. RHR for undeveloped roadways. Read the entire page →
From page 135... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 123 SLSG = DEVELOPED Overview This section provides an overview of the decision rules selected for the SLSG of Developed. The research team considered the following sources in creating the decision rules for developed roadways:  Rules used in USLIMITS2 (11) Read the entire page →
From page 136... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 124 Table 54. Overview of decision rules for SLSG = Developed. Read the entire page →
From page 137... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 125 Table 55. Decision matrix for sidewalk presence/width, sidewalk buffer, and pedestrian activity combinations for Developed SLSG. Read the entire page →
From page 138... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 126 Number of Lanes/Median Type (Undivided, TWLTL, Divided) Combinations The safety analyses conducted as part of NCHRP Project 17-76 (see Appendix D on Austin, Texas, and Appendix E on Washtenaw, Michigan) Read the entire page →
From page 139... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 127 The research team recommends that an appreciation for the bicycle activity level be retained within the SLS-Tool but separated from pedestrian activity. The examples for high bicyclist activity used in USLIMITS2 should be refined to reflect the use of the Expanded Functional Classification System in that downtown or CBD areas now fit within the urban core context. Read the entire page →
From page 140... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 128  Is a sidewalk separation (or buffer) present or not present between road (face of curb when curb and gutter are present or edge of travel lane when a shoulder is present) Read the entire page →
From page 141... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 129  Average AADT for the study period.  Average rate of total crashes and average rate of injury and fatal crashes (per 100 MVM) Read the entire page →
From page 142... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 130 Table 56. Average KABCO crash rate per 100 MVM from USLIMITS2 for Developed SLSG (i.e., context = urban, suburban, or rural town with roadway types of principal arterial, minor arterial, or collector) Read the entire page →
From page 143... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 131 Variables Considered but Not Included in SLS-Tool The research team considered the following variables but did not select them for the SLS-Tool:  Presence of a midblock crosswalk. Whether the presence of a single midblock crossing warrants a speed reduction would need to consider whether additional supplemental treatments are present, such as a rectangular rapid flashing beacon or pedestrian hybrid beacon. Read the entire page →
From page 144... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 132  Pedestrian activity (high, some, or negligible) Read the entire page →
From page 145... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 133 For roadways within the Full-Access SLSG, measured operating speeds are used to identify the suggested posted speed limit within the following two methods:  The 50th percentile speed rounded to the closest 5-mph increment (C50) Read the entire page →
From page 146... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 134 Signal Density USLIMITS2 includes the variable "signals per mile," and the variable was included in the Developed SLSG with break points at 3 and 4 signals per mile. These break points were supported by the findings from the analyses conducted using City of Austin, Texas, data (see Appendix D) Read the entire page →
From page 147... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 135 Bicyclist Activity Like the Developed SLSG, the suggested posted speed for a corridor within the FullAccess SLSG is a function of the level of bicyclist activity and the presence of a separated bike lane. Sidewalk Presence/Width, Sidewalk Buffer (Separation Distance between Pedestrian and Vehicles) Read the entire page →
From page 148... ... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 136  Number of access points (i.e., driveways and unsignalized intersections) in the section. Read the entire page →

From page 119...

... NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 107 APPENDIX F DECISION RULE DEVELOPMENT SLSG = LIMITED ACCESS Overview This section provides an overview of the decision rules selected for the SLSG of Limited Access.