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Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report (2021)

Chapter: Appendix A: Data Collection Procedures Guide

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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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Suggested Citation:"Appendix A: Data Collection Procedures Guide." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report. Washington, DC: The National Academies Press. doi: 10.17226/26393.
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228 A P P E N D I X A -DATA COLLECTION PROCEDURES GUIDE Data Collection Procedures Guide Purpose of Document This document described how geometric variables were be measured by the project team. Precise definitions are provided, and specific instructions for measuring the variables in Google Earth (when it is necessary to do so) are provided. This document is a companion to the Appendix B, which also lists non- geometric variables that do not require measurement by the project team. This document describes the research team’s approach for collecting data from Google Earth and post- processing it with MS Excel VBA macros. The team’s existing macro code was modified for Project 17- 89 and refinements to the data collection process were made as it occurred. Definition and Measurement of Geometric Data For geometric variables collected by the project team, definitions and instructions for measurement are provided below. Definitions remain consistent from facility to facility and state to state. The process for obtaining variable values in Google Earth assumes that pins are placed at points of interest, and macros in MS Excel read the coordinates of pins to determine distances. The “ruler” tool within Google Earth and other in-application measurement features are not used unless noted. Only variables that are simply observed or counted, like type of median barrier or number of lanes on a ramp, were directly entered into the database spreadsheet by the analyst. Use of pins for measurement-related variables preserves the start and end points of measurement, as well as the location of measurement (for cross-sectional measurements). This provided a record for checking the work of analysts, as well as a means of re-measuring variables under certain conditions if there was a need to redefine variables or a systemic error occurred. In this document, some variables are described in terms of a milepost location. For the purposes of associating crashes with sites and associating geometric elements with one another, a linear referencing system will be established for each facility studied. For HSIS states, the linear referencing system was obtained electronically and directly used (Method 1). For other states, the research team created their own linear referencing system (Method 2). The linear referencing system was created along the inside edge line that separates the leftmost travel lane (general purpose or HOV lane) from the shoulder (including a shoulder used for part-time travel). Separate referencing systems will be used for each direction of travel in Virginia because mileposts for each direction of travel differed by several tenths of a mile. The linear referencing system uses miles as the dimensional unit and values are reported as “mileposts” and referred to as “mileposts” in the remainder of this document. All crashes were assigned to a milepost, all sites are defined to start and end at a milepost, all geometric variables are associated with mileposts. Mileposts are defined to the thousandth of a mile. Table A-1 lists geometric variables and method by which each variable was measured. Definitions of these variables can be found in the Database Dictionary.

229 Table A-1. Geometric Variables and Method of Measurement Variable  Method of measurement  General  knowledge  Agency  provided  Assigned  by  research  team  Observed  in Google  Earth  Computed  with macros  from pins  dropped in  Google Earth  for this  variable  Computed  with macros  from pins  previously  dropped in  Google Earth  for other   variables  Manually  calculated  from other  variable  values  State  X Route  X Direction  X Site Type ‐ Shoulder Usage  X Site Type – Geometric X Number of Lanes X Lane Add/Drop   X Managed Lanes X Zipper Lane   X Speed Limit X X Opening Date  X  X Opening Date Known X Conversion X Conversion Known X Site Identification Number X Starting Point   X Ending Point   X Beginning Milepost X End Milepost   X Photo Date   X Length of Segment X  Length of Speed Change Lane   X  Number of Lanes on Ramp   X Type of Speed Change Lane, Lane 1   X Type of Speed Change Lane, Lane 2   X PTSU Transition Segment   X Starting Day X Ending Day X AADT  X Length of Curve X X  Radius of Curve X Length of Curve in Segment X Lane Width   X Right Shoulder Width   X Left Shoulder Width   X Width of Right Shoulder Used for Travel X Width of Left Shoulder Used for Travel   X Length of Right Side Rumble Strips   X Length of Left Side Rumble Strips   X Length of Roadside Barrier  X Offset to Roadside Barrier  X Median Plus Inside Shoulder Width  X Median Width  X Median Barrier Width  X Median Type  X Median Offset  X Median Barrier Length  X Median Barrier Offset  X Weaving Section   X Weaving Length   X  Distance to Nearest Upstream Entrance Ramp X  AADT of Nearest Upstream Entrance Ramp X

230 Distance to Nearest Downstream Exit Ramp X  AADT of Nearest Downstream Exit Ramp  X AADT of Entrance Ramp  X AADT of Exit Ramp  X Distance of Upstream Start of PTSU   X  Distance to Downstream End of PTSU X  Turnout Length X Shoulder Used for PTSU   X Sign Type  X GENERAL GUIDANCE Data are collected by creating a “segment” file in Google Earth. This file contains the coordinates of key points within and near a segment to help determine its geometric properties. The creation of segment file begins by loading the base segment file [i.e., SEG_base (rename).kml]. The structure of the segment file is shown in Figure A-1. It consists of the following folders: Begmp and Endmp – folder for the begin and end milepost placemarks. Begin Cross Section, End Cross Section, Mid-Point Cross Section – folder for placemarks describing the cross section at one milepost. Increasing Direction - folder for placemarks describing the median barrier pieces (for discontinuous median barriers) and roadside barrier pieces) on the increasing milepost direction of the freeway Decreasing Direction - folder for placemarks describing the median barrier pieces (for discontinuous median barriers) and roadside barrier pieces) on the decreasing milepost direction of the freeway Photo Date - folder is unused, but the photo date is typed into the folder name. Figure A-1. Segment File Structure Each folder (except PHOTO DATE) will contain multiple pins named in a specific format, and in some cases the pins are organized into subfolders named in a specific format. The structure of the folder and the information in the folder name is very important to the software that reads the file and interprets the data. DO NOT change the folder names, delete the folders, or rename the folders unless explicitly instructed to do so in these guidelines.

231 Google Earth Folder Manipulation Note that Google Earth locates points on the photo using the Placemark feature. A placemark is shown as a yellow pin. For this reason, placemarks are referred to hereafter as pins. Rename. A folder can be renamed by right-clicking on it and selecting “Rename”. Save. The segment folder can be saved by right-clicking on its name and selecting “Save Place As...”. Use the file name provided (it will be same as the folder name). Click on the drop down in bottom center of the open window for “Save as type” and select “.kml”. Click Save. Delete. A folder can be deleted by right-clicking on it and selecting “Delete”. Load. A segment file can be loaded using File, Open, and then navigating to the correct folder location for the file. Finding the Folder Location of a Pin. The folder containing a pin shown on the photo can be found by right clicking on the pin and selecting “Properties.” The folder location will be shown in Places (right side of Earth window). Moving the Folder Location of a Pin. A pin can be moved from one folder to another by right clicking on the pin in Places and select Cut. To put the pin at the top of the target folder, right click on the desired folder location and select Paste. Alternatively, to move the pin just after an existing pin in the target folder, right-click on the existing pin and select Paste. Moving a Folder Location. A folder can be moved using the same technique as followed for moving a pin (see previous paragraph). Copying the Folder Location of a Pin. A pin can be copied from one folder to another by right clicking on the pin in Places and select Copy. To put the pin at the top of the target folder, right click on the desired folder location and select Paste. Alternatively, to copy the pin just after an existing pin in the target folder, right-click on the existing pin and select Paste. Copying a Folder Location. A folder can be copied using the same technique as followed for copying a pin (see previous paragraph). Turning Off Folders. The pins shown on the photo can be hidden from view by clicking on the corresponding check mark in Places. Individual pins or entire folders of pins can be hidden in this manner. Clicking an open box will restore the check mark and reveal the pins. Resizing the Places View. The mouse can be used to grab the right border of the Places view and used to move this border left or right as needed to show the full folder or pin name. Similarly, the bottom of the Places view can be moved up or down. Google Earth Pin Manipulation Adding a Pin to a Folder. Click on the desired folder and highlight it. Then, click Add, Placemark; or cntl+shift+P; or click the yellow push pin on toolbar. Use the mouse to put the tip of the push pin on the desired point. Click OK. Renaming a Pin. A pin can be renamed in one of two ways. As one option, right-click on the pin shown on the photo and select Properties. Then click on the Name field and type the desired pin name (any combination of text and numbers is accepted). When done, click on OK. Moving Pin Location on the Photo. To adjust pin location on the photo, right-click on the pin and select Properties. Then, put the cursor on the pin and move it accordingly. The tip of the pin precisely defines the pin location. Viewing Pin Coordinates. The coordinates of a pin can be viewed by right-clicking on the pin and selecting Properties. The coordinates will be shown in a new window, as shown in Figure 3. This action

232 will also identify the folder in which the pin is located by highlighting it in the Places window (see Figure A-2). Figure A-2. Pin Coordinates. PLACEMARK PLACEMENT GUIDELINES This section provides guidelines for providing the information needed to describe a segment in the segment file. One file is populated for each road segment. Folder Name The file name convention is described below. SS-RRR-DD-XX.XXX where, SS = two letter US Postal Service abbreviation for the state name RRR = a state’s numerical designation of the route, with zeros preceding one or two digit route numbers DD = the posted direction of travel on the freeway (NB, SB, EB, WB) XX.XXX is begin milepost (begmp) Photo Date (Imagery Date) All of the pins in the folder must be located using one common photo. The date of this photo was previously established when the segment coordinates were determined. This date can be found in the spreadsheet and in the Photo Date folder (see Figure A-3). At the start of a session, turn on the Historical Imagery feature (either by clicking on the clock icon or click View, Historical Imagery). Before any pins are put in the segment folder, adjust the History slider until the photo’s “Imagery date” (lower left corner of photo) matches that in the spreadsheet. Note that the

233 History slider date may not agree exactly with the imagery date. These points are illustrated in Figure A- 3. Figure A-3. Imagery Date Identification. Never enter pins in the segment folder while the slider on the Historical Imagery date line is at the far right position. This is the “default” photo position. Newly inserted pins will not be date stamped when the slider is in the default photo position. Starting Point and Ending Point, Beginning Milepost and End Milepost The Beginning milepost and End milepost pins are placed on the marked edge line of the inside shoulder at the points where the criteria for starting and a segment are satisfied (See Site Data section of Database Dictionary). Both pins must be located in Begmp and Endmp Coordinates folder. Enter the name of the pin as the milepost number corresponding to the pin. Starting Point and Ending Point latitude/longitude values are read from the properties of the Beginning milepost and End milepost pins with macros. These provide a secondary means of future researchers being able to locate the site from the dataset alone after Project 17-89 is complete should it ever be separated from the associated Google Earth files. Cross-Section Variables The pins in this section are used to compute the following variables: Lane Width, Right Shoulder Width, Left Shoulder Width, Width of Right Shoulder Used for Travel, Width of Left Shoulder Used for Travel. This section describes the guidelines for locating the pins that describe the road cross section. Three folders are available for this purpose. The only difference is that each cross section folder is used to

234 describe the cross section at a different location on the segment (i.e., Begin milepost, the mid-segment point, and the End milepost). Number of Cross Section Folders to Use For segments less than 0.05 miles in length, populate the Begmp folder. For segments between 0.05 and 0.15 miles in length, populate the Begmp and Endmp folders. For segments more than 0.15 miles in length, populate all three folders. (See the section titled Cross Section Pin Location for additional discussion.) Number of Pins per Folder Up to one pin per folder. Each pin must be named. Its name is identified in parentheses in the folder name. Each name consists of two to three letters. If a particular point of reference does not exist on a given cross section, then the folder is left empty. Technique for Locating Pins on a Cross Section Draw a reference line on the photo at the desired location. The line must be perpendicular to the roadway’s centerline (use the Ruler tool to draw the line). Then locate the pins along this line. This technique will ensure that the computed widths are accurate. This line and the located pins for one cross section are shown in Figure 5. Each pin is placed on the reference line and at the point where the associated cross section element ends (or begins), as may be indicated by a pavement marking, barrier, change in coloration, or similar. In this case:  r for roadside edge  os2 for second outside edge line (present at some PTSU sites)  os for outside edge line  is for inside edge lane  m for median treatment location  iso for inside edge line for the other direction of travel The outside barrier does not begin or end within the extends of the photo, so pins associated with it do not appear in Figure A-4.

235 Figure A-4. Cross Section Pins. Figure A-5 illustrates pin placement in the vicinity of a gore point. The begin milepost reference line does not have a defined outside road edge. In this situation, the outside road edge pin “r” is located ½ of the distance between the markings delineating the edge of traveled way of the main lanes and ramp. The four pins associated with the barrier are discussed in a later section. Figure A-5. Cross Section near a Gore Point Cross Section Pin Location The “first-choice” location for pins in the Begmp cross section folder is a location near to the Begin milepost (i.e., within 25 to 35 feet). Similarly, the “first-choice” location for pins in the Endmp cross section folder is a location near to the End milepost (i.e., within 25 to 35 feet). If the candidate location

236 for a line is between the taper point and the taper-at-full-width point of a speed-change lane or a drop-add lane (i.e., the line is “on the taper”), then do the following: a. If two other cross section folders have been fully populated and three cross section lines are needed, then skip the location of this line. b. If one other cross section folder has been fully populated and two cross section lines are needed, then do one of the following: (1) if a second line can be located so that it is not “on the taper,” then locate pins on this line and add them to the appropriate cross section folder; or (2) if a second line cannot be located off of the taper, then skip the location of the second line. c. If the segment is entirely “on the taper” such that at least one side of the roadbed is being tapered at any point along the segment, then populate just one cross section folder using a line located at the point on the segment with the narrowest paved roadway width (= lane + shoulder width). For example, if the segment is 0.08 miles in length, then two folder locations are required. However, the begin milepost location is between the gore and taper points of a speed-change lane, so it is skipped. Instead, the Endmp and Mid-Point folders are fully populated. Transferring Cross Section Folders from Segment File to Segment File If the subject segment has an adjacent segment and the Endmp cross section folder has been previously populated in the adjacent segment’s folder, then the existing folder can be copied into the subject segment folder (i.e., these pins do not have to be manually re-entered). To illustrate this treatment of adjacent segments, consider the following example. Segment 1’s file has been fully populated with cross section pins, including those for the Endmp cross section. Next, the base segment file is started for Segment 2. The cross section data for the Endmp in Segment 1’s file is needed in Segment 2’s file because it represents the Begmp on Segment 2. The “Endmp Cross Section” folder will be copied from the Segment 1 file. Both files need to be loaded in Places at this point. First, the “Begmp Cross Section” folder (which is empty) is deleted from the Segment 2 file. Then, the Segment 1 file is opened and the “Endmp Cross Section” folder is copied from Segment 1 and pasted into the main folder for Segment 2. Finally, it is renamed in the Segment 2 folder from “Endmp Cross Section” to “Begmp Cross Section”. Note that the order of these main folders is not important (it is likely to change as a result of this paste operation) Roadside Barrier and Median Treatment Variables The pins in this section are used to compute the following variables: Roadside Barrier Start, Roadside Barrier End, Roadside Barrier Offset, Median Treatment Start, Median Treatment End, Median Treatment Offset. The following pins and pin names are used to describe roadside barrier and median treatment pieces:  barX – point on a barrier, where X = number of point, X = 1, 2, 3, ...  offX – projection of “barX” to the outside edge of traveled way, where X = number of point As described in the data dictionary, median treatments may be cable barriers, guardrail barriers, concrete barriers, obstructions, or no obstructions. In the remainder of this section, all are referred to as “barriers” (although “no obstruction” is explicitly a no barrier condition) For any point identified on a piece of barrier using “barX”, there must be a corresponding point “offX” that is located on the outside edge of traveled way and at the closest possible distance from “barX” (this point will be along a line through “barX” that is perpendicular to the edge of traveled way). Note that median treatments that are continuous for the length of the segment are described in the Cross Section folders. They are not described in these folders. Only barrier pieces located on (i.e., adjacent to) the segment are used to populate the barrier subfolders (unlike gore and taper points). If a barrier piece starts in the subject segment and continues into the next

237 segment, then only that portion of the barrier that is on the subject segment is referenced by pins in the segment folder. Subfolder Content All pins in a subfolder are used to describe one piece of barrier. Subfolders named r1, r2, r3, etc. contain data for outside (right side) barriers, and subfolders names l1, l2, l3, etc. contain data for median (left side) barriers. A minimum of four pins are needed for this purpose (two at each end: bar 1, off1 at one end and bar 2 and off 2 at the other end). All of the pins associated with one piece of barrier are located in one subfolder. Maximum Number of Subfolders A maximum number of 10 barrier pieces can be described for the roadside. Similarly, 10 barrier pieces can be used to describe median treatments for this roadbed. Maximum Number of Pins Per Folder A maximum of 30 pins can be added to any one barrier subfolder (i.e., a maximum of 15 “barX” pins and 15 “offX” pins). A minimum of four pins are needed in the folder. Procedure for Defining Subfolder Content 1. For each barrier piece, locate one “barX” pin (and associated “offX” pin) at the start of the barrier, where the start of the barrier is the most upstream point relative to the direction of travel. Use a value of “1” for the X variable at this point (i.e., “bar1”, “off1”). 2a. If the road is straight for the length of the barrier, the offset distance between barrier and edge of traveled way does not change or, it changes at a constant rate along the barrier, then locate one “barX” pin (and associated “offX” pin) at the end of the barrier, where the end of the barrier is the most downstream point relative to the direction of travel. Use a value of “2” for the X variable at this point. This condition is shown in Figure A-6a and Figure A-6b. 2b. If the conditions in 2a do not apply, then move along the barrier in the direction of travel and locate additional pairs of “barX” and “offX”. Pin pairs should not be closer than 20 ft (as measured along the edge of traveled way) and should be spaced along the barrier piece such that the middle ordinate between “offX” pins does not exceed 6 ft (i.e., about the width of the typical full size sedan). Use values of “2”, “3”, etc. as needed for the X variable. This condition is shown in Figure A-6c. 3. At least one pair of pins should be used to locate the end of the barrier. The X variable at this point should have the largest value of all pins associated with this barrier. If there is any doubt about whether Step 2a or 2b applies, use Step 2b. Only that portion of the barrier that is “on” (i.e., adjacent to) the segment is referenced by pins in the segment folder. Similarly, if a barrier is located along the speed- change lane, then only that portion adjacent to the segment is reference by pins in the segment folder. Both of these points are illustrated in Figure A-6 where a piece of barrier is located partially on the ramp and partially on the segment. Four pins are used to define the portion of barrier that is on the segment. An example barrier location is shown in Figure A-7. It illustrates the application of procedure Steps 1, 2b, and 3, where X = 1, 2, and 3. With regard to Step 2b, one additional pair of pins is used at a mid- barrier location where there is a notable change in the angle between the barrier and the edge of traveled way. All pins shown are located in one subfolder.

238 Figure A-6. Basic Barrier Pin Placement Rules

239 Figure A-7. Example Pin Location for Roadside Barrier Piece. An example barrier location is shown in Figure A-8. It illustrates the application of procedure Steps 1, 2b, and 3, where X = 1, 2, 3, 4, 5, and 6. Note that two pairs of pins are used at the beginning of the barrier, a second pair is located at the start of the curve, and additional pairs are spaced along the curve. All pins shown are located in one subfolder. An example barrier location is shown in Figure 10. It illustrates the application of procedure Steps 1, 2b, and 3, where X = 1, 2, 3, and 4. With regard to Step 2b, two additional pairs of pins are used at mid-barrier locations. This example is similar to that shown in Figure 8 except that it illustrates the need for and additional pin pair (X =3). In this instance, it is the edge of traveled way curving away from the straight barrier that dictates the need for this pin pair. If the distance between off3 and off4 is greater than 40 ft, then an additional pin pair should be located midway between these two pairs (the new pair would be numbered X=4 and the last pair would be renumbered as X=5). All pins shown are located in one subfolder.

240 Figure A-8. Example Pin Locations for Continuous Roadside Barrier Piece Figure A-9. Example Pin Location for Complex Shape Barrier Piece. Curve-related Variables Curves can span multiple segments. A separate system of Google Earth pins and folders and Excel VBA Macros are used to process curve data. The pins in that system are used to compute the following variables: Length of Curve, Radius of Curve, Length of Curve in Segment. They are placed on the inside (left) edge line of the freeway The following pins and pin names are used to describe horizontal curves:

241  s1 - Locate on tangent, at least 150 ft before the curve  s2 - Locate on tangent, at least 100 ft after s1 and before the curve  m1 - Use for all analyses. If a compound curve is suspected, points m1, m2, ... mN should follow points a1, a2, ..., aN and precede points b1, b2, ... bN.  m2 - Use for all analyses. Locate at least 50 ft from m1. Points m1, m2, ... mN are located along the curve with shorter spacing near the midpoint of the curve. At least 3 points are needed.  mN - Locate at least 50 ft from last point.  e1 - Locate on tangent, at least 50 ft after the curve  e2 - Locate on tangent, at least 100 ft from e1 in the direction away from the curve (i.e., at least 150 ft from the curve) Folder Content All pins used to describe a curve are placed in the same folder. Pins for the tangents before and after the curve can be located beyond the Beginning milepost and End milepost pins because the tangents will be beyond the limits of the segment itself. Maximum Number of Pins Per Folder Only one set of these pins can be used per folder because a maximum of 34 pins can be added to any one curve folder (i.e., two for the approach tangent, up to 30 for the curve, and two for the departure tangent). Quality Assurance/Quality Control This section describes QA/QC procedures for the geometric variables that were collected for Project 17-89.  A master data file will be an Excel spreadsheet kept on the network drive. Data will only be entered into this master file after it has been reviewed and approved by a senior staff member. The last section of the Database Dictionary document describes the structure of this spreadsheet.  Junior researchers will reduce data using an Excel spreadsheet with their initials at the end of the file name that has the same worksheets and field headings as the master file. These files are referred to as “individual files”. When they complete a portion of data reduction and pass the reduced data onto the principal investigator or another senior staff person for review, they will highlight the cells containing the data in yellow. When the review is complete, the principal investigator will change the cell highlighting from yellow to green and copy the data into the master file. The principal investigator will indicate in columns in the master file the initials of the person who reduced the data, the initials of the person who checked the data, and the date that checking was completed and transferred into the master file. It is anticipated at this time that all geometric data will be reduced by a single junior researcher, but the process described above is scalable and will accommodate the use of additional staff if necessary.  The Excel macros that process Google Earth pin data provide 1) built-in warning messages for data outside of typical values, such as a lane width greater than 14 feet and 2) built-in error messages if the placement or name of pins violates the conventions needed by the software to run properly.  If multiple measurements are required for a given variable, the associated math should be performed within the Excel file rather than mentally or with a calculator. For example, =average(8, 10) or =sum(32+95)

242  The number of geometric variables being extracted and the definitions of them (in the database dictionary) exceed what any person will be able to memorize and efficiently extract at once. Therefore, instead of a junior staff person extracting all geometric data for a given site, they will extract a “wave” of five to ten related variables for an entire facility, then return to the start of the facility and extract the next “wave”. The research team has successfully extracted data with the “wave” approach on past projects.  The first time a junior engineer extracts variables in a given wave, the principal investigator or another a senior staff person will conduct a work session with them to measure the variables for several sites together and ensure the junior engineer fully understands the measurement process.  When the junior engineer completes a wave for an entire facility or at the end of each week (whichever happens first), the junior engineer will pass their individual file to the principal investigator for checking and indicate the number of hours it took to reduce the data.  The principal investigator or another senior staff person will then check the data and record the number of hours to do so. The following checks will occur: o A manual review of the data at a glance to identify illogical values of data (for example, a “Width of right shoulder used for travel” value of 4 feet) or sequences of data (for example, frequent changes of speed limit from one segment to the next) o Summary calculations to identify impossible conditions, such as a value of “length of barrier” that this greater than the length of the segment or a “distance to downstream end of PTSU” that exceeds the length of the facility o Occasional spot checks (i.e. re-reducing a site’s data to verify results)

Next: Appendix B: Database Dictionary »
Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report Get This Book
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Part-time shoulder use is a congestion relief strategy that allows use of the left or right shoulders as travel lanes during some, but not all, hours of the day.

The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 309: Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report describes the development of crash prediction models for freeways with PTSU operation.

Supplemental to the document is a Freeway Analysis Tool, which includes BOS Data, S D PTSU Data, and a Prediction Tool, as well as NCHRP Web-Only Document 309: Safety Performance of Part-Time Shoulder Use on Freeways, Volume 1: Informational Guide and Safety Evaluation Guidelines.

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