Traffic Data Computation Method - POCKET GUIDE

Sep 13, 2026

Upload by Elsa

Traffic Data Computation Method Pocket Guide provides a structured reference for calculating key traffic engineering inputs used in transportation planning and roadway design. It covers essential measures such as speed percentiles, AADT and ADT variants, truck and ESAL-related computations, capacity, directional design volumes, intersection and signal parameters, and vehicle-class conversions. The pocket guide also consolidates supporting concepts like free flow, headway, saturation flow, K-factors, occupancy, VMT, and volume-to-capacity relationships, enabling consistent, objective application of FHWA methodology.

LanguageEnglish

CategoryGeneral

FormatPDF

Pages116

Reading Time41 min

AccessFree to download

Preface

85th Percentile Speed

Annual Average Daily Traffic (AADT)

Annual Average Daily Truck Traffic (AADTT)

Average Daily Traffic (ADT)

Axle Correction Factor (ACF)

Capacity

Change Rate

Combination Unit Truck AADT

Critical Speed

Design Hour

Design Vehicles

Design Volume

Directional Design-Hour Volume (DDHV)

Directional Factor

Directional Flow Rate and Ratio

Equivalent Single Axle Load (ESAL)

Free Flow

Future AADT

Gross Vehicle Weight (GVW)

Headway

K-Factor

Lane Groups

Load Spectra

Month of Year and Day of Week Factors

Monthly Average Daily Traffic (MADT)

Number of Intersections of Other Type

Number of Signalized Intersections

Number of Stop Sign Intersections

Passenger Car Equivalent (PCE)

Peak Hour Factor (PHF)

Percent Green Time

Percent Peak Combination Unit Trucks

Percent Peak Single Unit Trucks & Buses

Roadway Occupancy

Saturation Flow

Saturation Headway

Short Term Count ADT by Vehicle Class to AADT by Vehicle Class Conversion

Short Term Count ADT to AADT Conversion

Signal Type

Single Unit Truck & Bus AADT

Time of Day (TOD) Factor

Traffic Demand

Turning Radius

Vehicle Class Factoring

Vehicle Density

Vehicle Miles Traveled (VMT)

Vehicle Speed

Volume and Volume-to-Capacity Ratio

Index

Publication No. FHWA-PL-18-027 August 2018 Traffic Data Computation Method POCKET GUIDE NOTICE This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document. QUALITY ASSURANCE STATEMENT The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. 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 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 ..................

FAQs

What purpose does the Traffic Data Computation Method Pocket Guide serve?

It consolidates FHWA traffic computation concepts and measures into a structured reference for calculating common inputs used in traffic analysis and roadway design.

Which traffic volume measures are included in the guide?

The guide includes AADT-related measures (AADT, ADT, MADT) and truck-focused variants such as AADTT, along with directional design-hour volumes and demand-related parameters.

Does the pocket guide cover both vehicle speed and roadway capacity concepts?

Yes. It includes topics such as 85th percentile speed, critical speed, headway, free flow, saturation flow/headway, capacity, and volume-to-capacity ratio relationships.

Sep 13, 2026

Upload by Elsa