Loop- and Length-Based Vehicle Classication, Federal Highway Administration – Pooled Fund Program [TPF-5(192)] Erik Minge, Primary Author SRF Consulting Group, Inc. Minneapolis, Minnesota November 2012 Research Project Final Report 2012-33 To request this document in an alternative format, please contact the Affirmative Action Office at 651-366-4723 or 1-800-657-3774 (Greater Minnesota); 711 or 1-800-627-3529 (Minnesota Relay). You may also send an e-mail to [email protected]. (Please request at least one week in advance). Technical Report Documentation Page 1. Report No. 2. 3. Recipients Accession No. MN/RC 2012-33 4. Title and Subtitle 5. Report Date Loop- and Length-Based Vehicle Classification, Federal November 2012 Highway Administration – Pooled Fund Program [TPF-5(192)] 6. 7. Author(s) 8. Performing Organization Report No. Erik Minge, Scott Petersen, Herbert Weinblatt, Benjamin Coifman, and Earl Hoekman 9. Performing Organization Name and Address 10. Project/Task/Work Unit No. SRF Consulting Group, Inc. One Carlson Parkway, Suite 150 11. Contract (C) or Grant (G) No. Minneapolis, MN 55416 (C) 95029 12. Sponsoring Organization Name and Address 13. Type of Report and Period Covered Minnesota Department of Transportation Final Report Research Services 14. Sponsoring Agency Code 395 John Ireland Boulevard, MS 330 St. Paul, MN 55155 15. Supplementary Notes http://www.lrrb.org/pdf/201233.pdf 16. Abstract (Limit: 250 words) While most vehicle classification currently conducted in the United States is axle-based, some applications could be supplemented or replaced by length-based data. Common length-based methods are more widespread and can be less expensive, including loop detectors and several types of non-loop sensors (both sidefire and in-road sensors). Loop detectors are the most frequently deployed detection system and most dual-loop installations have the capability of reporting vehicle lengths. This report analyzes various length-based vehicle classification schemes using geographically diverse data sets. This report also conducted field and laboratory tests of loop and non-loop sensors for their performance in determining vehicle length and vehicle speed. The study recommends a four bin length scheme with a fifth bin to be considered in areas with significant numbers of long combination vehicles. The field and laboratory testing found that across a variety of detection technologies, the sensors generally reported comparable length and speed data. 17. Document Analysis/Descriptors 18. Availability Statement Vehicle classification scheme, Vehicle detection, Vehicle No restrictions. Document available from: length, Speed detection, Loop detector, Non-intrusive National Technical Information Services, technologies Alexandria, Virginia 22312 19. Security Class (this report) 20. Security Class (this page) 21. No. of Pages 22. Price Unclassified Unclassified 106 Loop- and Length-Based Vehicle Classification, Federal Highway Administration – Pooled Fund Program [TPF-5(192)] Final Report Prepared by: Erik Minge Scott Petersen Herbert Weinblatt Benjamin Coifman Earl Hoekman SRF Consulting Group, Inc. Minneapolis, Minnesota November 2012 Published by: Minnesota Department of Transportation Research Services 395 John Ireland Boulevard, MS 330 St. Paul, Minnesota 55155 This report represents the results of research conducted by the authors and does not necessarily represent the views or policies of the Minnesota Department of Transportation or SRF Consulting Group. This report does not contain a standard or specified technique. The authors, the Minnesota Department of Transportation, and SRF Consulting Group do not endorse products or manufacturers. Any trade or manufacturers’ names that may appear herein do so solely because they are considered essential to this report. Acknowledgments The project was guided by participating state agencies that are part of this pooled initiative. These individuals comprised the Technical Advisory Committee (TAC): Alaska Maryann Dierckman Colorado Aaron Moss Connecticut Anne-Marie McDonnell Florida Steven Bentz Idaho Jack Helton Illinois Rob Robinson Michigan Jim Kramer Minnesota Gene Hicks New York Kurt Matias Ohio Dave Gardner and Lindsey Pflum Pennsylvania Andrea Bahoric Texas Bill Knowles Washington Ken Lakey Wisconsin John Williamson Wyoming Sherman Wiseman Table of Contents Chapter 1: Project Overview ................................................................................................. 1 1.1 Introduction ...................................................................................................................... 1 1.2 Project Goals and Objectives ........................................................................................... 1 1.3 Project Team .................................................................................................................... 2 1.3.1 Project Audience ....................................................................................................... 2 Chapter 2: Literature Review ................................................................................................ 3 2.1 Vehicle and Loop Length ................................................................................................. 3 2.1.1 Magnetic Length ....................................................................................................... 3 2.1.2 Physical Length ......................................................................................................... 3 2.1.3 Effective Loop Length ............................................................................................... 3 2.2 Loop Characteristics ......................................................................................................... 4 2.3 Loop Detector Operation Theory ..................................................................................... 7 2.4 Loop Detector Errors ........................................................................................................ 9 2.4.1 Documented Research of Detector Errors ................................................................ 9 2.4.2 Causes of Length-Based Error................................................................................ 10 2.5 Length Classification Issues ........................................................................................... 12 2.6 Inductive Signature-Based Detectors ............................................................................. 14 2.7 Non-Loop Detectors ....................................................................................................... 16 2.8 Uses for Length-Based Classification Data ................................................................... 17 2.9 Literature Review Summary .......................................................................................... 18 Chapter 3: Length-Based Vehicle Classification Schemes ................................................ 19 3.1 Development and Evaluation of LBVC Schemes .......................................................... 19 3.1.1 Length-Based Classification Schemes .................................................................... 19 3.1.2 Data......................................................................................................................... 20 3.1.3 Axle Classification .................................................................................................. 22 3.1.4 LBVC Scheme Evaluations Using LTPP Data from All Sites Combined ............... 23 3.1.5 Locational and Temporal Influences ...................................................................... 31 3.1.6 Urbanized Area Influence ....................................................................................... 36 3.1.7 Length Bins and Axle Classes ................................................................................. 37 3.1.8 Estimation of Load Spectra Based on LBVC .......................................................... 37 3.2 Length-Based Classification Scheme Recommendations .............................................. 39 3.2.1 Seasonal and Geographical Variation.................................................................... 40 Chapter 4: Detector Calibration Procedure ....................................................................... 41 4.1 Recommended Calibration Process – Probe Vehicle Runs ............................................ 41 4.2 Calibration Overview ..................................................................................................... 42 4.3 Probe Vehicle Calibration Process ................................................................................. 43 4.4 Probe Vehicle Validation Process .................................................................................. 43 4.5 Alternative Calibration Methods .................................................................................... 44 4.6 Rules of Thumb for Detector Calibration ...................................................................... 47 Chapter 5: Field and Laboratory Tests .............................................................................. 48 5.1 Test Methodology .......................................................................................................... 48 5.1.1 Detectors Tested...................................................................................................... 48 5.1.2 Field Test Description............................................................................................