Traffic Data Computation Method - Transportation

Publication No. FHWA-PL-18-027 August 2018

Traffic Data Computation Method

POCKET GUIDE

NOTICE

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Table of Contents

Table of Contents .............................................................. i List of Figures .................................................................. iv List of Tables .................................................................... v Abbreviations .................................................................. vii Preface .............................................................................1 85th Percentile Speed........................................................4 Annual Average Daily Traffic (AADT)................................6 Annual Average Daily Truck Traffic (AADTT)....................8 Average Daily Traffic (ADT)............................................10 Axle Correction Factor (ACF) ..........................................12 Capacity .......................................................................... 14 Change Rate ...................................................................16 Combination Unit Truck AADT ........................................18 Critical Speed..................................................................20 Design Hour....................................................................22 Design Vehicles...............................................................24 Design Volume................................................................26 Directional Design-Hour Volume (DDHV)........................28 Directional Factor ...........................................................30 Directional Flow Rate and Ratio......................................32 Equivalent Single Axle Load (ESAL) ................................34 Free Flow........................................................................36 Future AADT ...................................................................38 Gross Vehicle Weight (GVW) ..........................................40

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Headway .........................................................................42 K-Factor ..........................................................................44 Lane Groups ...................................................................46 Load Spectra...................................................................48 Month of Year and Day of Week Factors ........................50 Monthly Average Daily Traffic (MADT)............................52 Number of Intersections of Other Type ..........................54 Number of Signalized Intersections ................................56 Number of Stop Sign Intersections .................................58 Passenger Car Equivalent (PCE) .....................................60 Peak Hour Factor (PHF) ..................................................62 Percent Green Time ........................................................64 Percent Peak Combination Unit Trucks ...........................66 Percent Peak Single Unit Trucks & Buses .......................68 Roadway Occupancy.......................................................70 Saturation Flow...............................................................72 Saturation Headway........................................................74 Short Term Count ADT by Vehicle Class to AADT by Vehicle Class Conversion ................................................76 Short Term Count ADT to AADT Conversion...................78 Signal Type .....................................................................80 Single Unit Truck & Bus AADT ........................................82 Time of Day (TOD) Factor ..............................................84 Traffic Demand ...............................................................86 Turning Radius................................................................88 Vehicle Class Factoring ...................................................90

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Vehicle Density ...............................................................92 Vehicle Miles Traveled (VMT) .........................................94 Vehicle Speed .................................................................96 Volume and Volume-to-Capacity Ratio ...........................98 Index ............................................................................100

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