The National Academies Press

Currently Skimming:

Pages 226-240

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.

From page 226... ... 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) Read the entire page →
From page 227... ... 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 Read the entire page →
From page 228... ... 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. Read the entire page →
From page 229... ... 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. Read the entire page →
From page 230... ... 232 will also identify the folder in which the pin is located by highlighting it in the Places window (see Figure A-2) Read the entire page →
From page 231... ... 233 History slider date may not agree exactly with the imagery date. These points are illustrated in Figure A3. Read the entire page →
From page 232... ... 234 describe the cross section at a different location on the segment (i.e., Begin milepost, the mid-segment point, and the End milepost) Read the entire page →
From page 233... ... 235 Figure A-4. Cross Section Pins. Read the entire page →
From page 234... ... 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. Read the entire page →
From page 235... ... 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. Read the entire page →
From page 236... ... 238 Figure A-6. Basic Barrier Pin Placement Rules Read the entire page →
From page 237... ... 239 Figure A-7. Example Pin Location for Roadside Barrier Piece. Read the entire page →
From page 238... ... 240 Figure A-8. Example Pin Locations for Continuous Roadside Barrier Piece Figure A-9. Read the entire page →
From page 239... ... 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, ... Read the entire page →
From page 240... ... 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. Read the entire page →

From page 226...

... 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)