The Effect of Law Enforcement Deployment Patterns on Motorists’ Speeds
Total Page:16
File Type:pdf, Size:1020Kb
THE EFFECT OF LAW ENFORCEMENT DEPLOYMENT PATTERNS ON MOTORISTS’ SPEEDS Final Report SPR 304-161 by Kevin J. Haas, P.E. Barnie P. Jones, Ph.D. Alan R. Kirk for Oregon Department of Transportation Research Unit 200 Hawthorne Ave. SE, Suite B-240 Salem OR 97301-5192 and Federal Highway Administration 400 Seventh Street S.W. Washington, DC 20590 December 2003 Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA-OR-DF-04-04 4. Title and Subtitle 5. Report Date The Effect of Law Enforcement Deployment Patterns on Motorists’ December 2003 Speeds 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Kevin J. Haas, P.E., Barnie P. Jones, Ph.D. and Alan R. Kirk 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Oregon Department of Transportation Research Unit 11. Contract or Grant No. 200 Hawthorne Ave. SE, Suite B-240 Salem, Oregon 97301-5192 SPR 304 - 161 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Oregon Department of Transportation Final Report Research Unit and Federal Highway Administration 200 Hawthorne Ave. SE, Suite B-240 400 Seventh Street S.W. Salem, Oregon 97301-5192 Washington, DC 20590 14. Sponsoring Agency Code 15. Supplementary Notes 16. Abstract The combination of increased demands on Oregon’s transportation system and limited law enforcement resources has led the Oregon Department of Transportation (ODOT) to investigate whether a relationship exists between motorists’ speeds and law enforcement levels. If an optimum level of law enforcement could be identified that reduces the number of motorists driving in an unsafe manner, the end result could be a more efficient deployment of scarce law enforcement resources. This study deployed enhanced law enforcement patrols at six study sites in Oregon to evaluate the effects of law enforcement presence on vehicle speeds. Investigators first recorded baseline speeds for a two-month period prior to the commencement of enhanced enforcement. Enhanced patrols varied from 10 to 25 hours per week on either fixed or random schedules. Enforcement at each site was on an eight-week cycle: two weeks of enhanced patrols followed by six weeks of normal patrols. The data analysis compared median and 85th percentile speeds in the baseline and enhanced enforcement conditions. Baseline and enhanced enforcement data were also compared for the percent of vehicles traveling over the posted speed at each site. The findings showed that enhanced patrols resulted in small but statistically significant reductions in speed at most of the test sites. Both median and 85th percentile speeds were significantly higher than posted speeds at all of the study sites in both the baseline and the enhanced enforcement conditions. 17. Key Words 18. Distribution Statement speed limits, basic rule, police patrol, traffic law enforcement, th Copies available from NTIS, and online at field study, data collection, speeding, median speed, 85 http://www.odot.state.or.us/tddresearch percentile speed, optimum deployment 19. Security Classif. (of this report). 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified 56 Technical Report Form DOT F 1700.7 (8-72) Reproduction of completed page authorized Printed on recycled paper i SI* (MODERN METRIC) CONVERSION FACTORS APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FROM SI UNITS Symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find Symbol LENGTH LENGTH In Inches 25.4 Millimeters Mm Mm Millimeters 0.039 inches in Ft Feet 0.305 Meters M M Meters 3.28 feet ft Yd Yards 0.914 Meters M M Meters 1.09 yards yd Mi Miles 1.61 Kilometers Km Km Kilometers 0.621 miles mi AREA AREA In2 Square inches 645.2 millimeters mm2 mm2 millimeters squared 0.0016 square inches in2 Ft2 Square feet 0.093 meters squared M2 m2 meters squared 10.764 square feet ft2 Yd2 Square yards 0.836 meters squared M2 Ha Hectares 2.47 acres ac Ac Acres 0.405 Hectares Ha km2 kilometers squared 0.386 square miles mi2 Mi2 Square miles 2.59 kilometers squared Km2 VOLUME VOLUME ML Milliliters 0.034 fluid ounces fl oz ii Fl oz Fluid ounces 29.57 Milliliters ML L Liters 0.264 gallons gal Gal Gallons 3.785 Liters L m3 meters cubed 35.315 cubic feet ft3 Ft3 Cubic feet 0.028 meters cubed m3 m3 meters cubed 1.308 cubic yards yd3 Yd3 Cubic yards 0.765 meters cubed m3 MASS NOTE: Volumes greater than 1000 L shall be shown in m3. G Grams 0.035 ounces oz MASS kg Kilograms 2.205 pounds lb Oz Ounces 28.35 Grams G Mg Megagrams 1.102 short tons (2000 lb) T Lb Pounds 0.454 Kilograms Kg TEMPERATURE (exact) T Short tons (2000 lb) 0.907 Megagrams Mg LC Celsius temperature 1.8C + 32 Fahrenheit LF TEMPERATURE (exact) LF Fahrenheit 5(F-32)/9 Celsius LC temperature temperature * SI is the symbol for the International System of Measurement (4-7-94 jbp) ACKNOWLEDGEMENTS The authors would like to thank the following for their assistance in the conduct of the research and the preparation of this report: McGregor Lynde, Joni Reid and Deborah Martinez, Oregon Department of Transportation Research Unit Jeremy Williams and Michelle Baldwin (Student Interns), Oregon Department of Transportation Research Unit Larry Christianson, Oregon Department of Transportation Safety Division Steve Vitolo, Oregon Department of Transportation Safety Division Andrew Griffith, Texas Department of Transportation DISCLAIMER This document is disseminated under the sponsorship of the Oregon Department of Transportation and the United States Department of Transportation in the interest of information exchange. The State of Oregon and the United States Government assume no liability of its contents or use thereof. The contents of this report reflect the view of the authors who are solely responsible for the facts and accuracy of the material presented. The contents do not necessarily reflect the official views of the Oregon Department of Transportation or the United States Department of Transportation. The State of Oregon and the United States Government do not endorse products of manufacturers. Trademarks or manufacturers’ names appear herein only because they are considered essential to the object of this document. This report does not constitute a standard, specification, or regulation. iii iv THE EFFECT OF LAW ENFORCEMENT DEPLOYMENT PATTERNS ON MOTORISTS’ SPEEDS TABLE OF CONTENTS 1.0 INTRODUCTION..................................................................................................................1 1.1 PROBLEM STATEMENT..................................................................................................1 1.2 OBJECTIVES AND RESEARCH METHODOLOGY ......................................................1 2.0 LITERATURE REVIEW .....................................................................................................3 3.0 SITE SELECTION................................................................................................................5 4.0 FIELD STUDY METHODS .................................................................................................7 4.1 DEVELOPMENT OF LAW ENFORCEMENT PATTERNS............................................7 4.2 DATA COLLECTION ........................................................................................................8 4.3 SITE DATA.........................................................................................................................9 5.0 ANALYSIS OF RESULTS..................................................................................................11 5.1 ENHANCED ENFORCEMENT OVERVIEW.................................................................11 5.2 MEDIAN (50TH PERCENTILE) SPEEDS ......................................................................12 5.3 85TH PERCENTILE SPEEDS............................................................................................12 5.4 PERCENT OF VEHICLES TRAVELING OVER POSTED SPEED ..............................12 5.5 PERCENT OF VEHICLES TRAVELING 10 MPH (16 KM/H) OR GREATER OVER THE POSTED SPEED...........................................................................................12 5.6 STATISTICAL TESTING.................................................................................................13 5.6.1 Analysis of Gates speed data .....................................................................................14 5.6.2 Analysis of Alsea speed data .....................................................................................15 5.6.3 Analysis of Monmouth statistical data.......................................................................15 5.6.4 Analysis of Aumsville statistical data........................................................................16 5.6.5 Analysis of Oak Knoll statistical data........................................................................16 5.6.6 Analysis of Noti statistical data .................................................................................17 5.6.7 Chi-square analysis summary ....................................................................................17 5.7 DISCUSSION OF FIELD DATA .....................................................................................18 6.0 CONCLUSIONS AND RECOMMENDATIONS.............................................................21 6.1 CONCLUSIONS................................................................................................................21 6.2 RECOMMENDATIONS...................................................................................................22