2020 California Manual for Setting (Revised February 2020) Speed Limits Division of Traffic Operations California Department of Transportation Copyright 2020 California Department of Transportation. All Rights Reserved. California Manual for Setting Speed Limits Disclaimer This manual (Manual) does not constitute a standard, specification, or regulation. This Manual is not intended to replace the existing Caltrans mandatory or advisory standards and is not intended to be a substitute for engineering knowledge, experience or judgment. This Manual promotes better access to helpful information and concepts from various agencies and organizations. Caltrans acknowledges the existence of other practices and provides this Manual for reference and direction for those responsible for making professional engineering or other design decisions. Please be aware that Caltrans is not the author of the external sources contained in this Manual and is therefore not responsible for errors or omissions that may be contained within those external sources. The references contained in this Manual are provided for the user’s convenience. The content or information in such references is the sole responsibility of their respective authors and/or owners. Copyright 2020 California Department of Transportation. All Rights Reserved. Page 1 California Manual for Setting Speed Limits This page has intentionally been left blank. Page 2 Copyright 2020 California Department of Transportation. All Rights Reserved. California Manual for Setting Speed Limits California Manual for Setting Speed Limits Division of Traffic Operations California Department of Transportation 2020 Copyright 2020 California Department of Transportation. All Rights Reserved. Page 3 California Manual for Setting Speed Limits This page has intentionally been left blank. Page 4 Copyright 2020 California Department of Transportation. All Rights Reserved. California Manual for Setting Speed Limits Table of Contents CHAPTER 1 INTRODUCTION........................................................................................................................11 1.1 Overview.....................................................................................................................................11 1.1.1 Purpose of this Manual .......................................................................................................11 1.1.2 Users of this Manual ...........................................................................................................11 1.1.3 Responsibilities...................................................................................................................11 1.2 General Concepts........................................................................................................................11 1.2.1 Basic Speed Law.................................................................................................................12 1.2.2 Prima Facie Speed Limits by Statute ..................................................................................13 1.2.3 Speed Limits Requiring an Engineering and Traffic Survey ..............................................13 1.2.4 Authority to Set Speed Limits.............................................................................................13 1.2.5 Speed Traps.........................................................................................................................13 1.3 Factors Affecting Drivers’ Speeds..............................................................................................14 1.3.1 Design and Physical Characteristics of the Roadway.........................................................14 1.3.2 The Vehicle.........................................................................................................................14 1.3.3 The Driver...........................................................................................................................15 1.3.4 Traffic .................................................................................................................................15 1.3.5 Weather and Visibility ........................................................................................................15 1.3.6 Other Roadway Users .........................................................................................................15 1.3.7 Vehicle Operating Speeds...................................................................................................16 CHAPTER 2 REGULATORY AND ADVISORY SPEEDS...................................................................................17 2.1 Overview.....................................................................................................................................17 2.2 Regulatory Speed Zones Established by an Engineering and Traffic Survey.............................17 2.2.1 Regulatory Speeds...............................................................................................................17 2.2.2 Highway Approaches to Incorporated Municipalities ........................................................18 2.2.3 Minimum Speeds ................................................................................................................18 2.2.4 Signs within Cities and Towns............................................................................................19 2.2.5 Advisory Speeds .................................................................................................................19 2.2.6 Regulatory Versus Advisory Speeds...................................................................................19 2.2.7 Advisory Speeds in Regulatory Speed Zones .....................................................................20 2.3 Temporary Traffic Control Advisory and Regulatory Speeds....................................................20 2.3.1 Advisory Temporary Traffic Control Speeds .....................................................................21 2.3.2 Temporary Traffic Control Speed Limit in Construction Work Zones ..............................21 Copyright 2020 California Department of Transportation. All Rights Reserved. Page 5 California Manual for Setting Speed Limits 2.3.3 Request for Maintenance Regulatory Temporary Traffic Control Speed Zones ................ 25 2.3.4 Signs Installed by the Contractor ........................................................................................ 25 2.4 School Speed Zones .................................................................................................................... 26 2.4.1 Planning for School Areas .................................................................................................. 26 2.4.2 School Zones under Local Authority .................................................................................. 26 2.4.3 Signs for School Areas ........................................................................................................ 27 2.4.4 Intervals of Operation ......................................................................................................... 27 2.5 Reduced Truck Speed Limit on Descending Grades .................................................................. 28 2.6 Private Roads .............................................................................................................................. 29 2.7 Variable Speed Limits ................................................................................................................. 30 2.8 Setting a Speed Limit at 70 mph ................................................................................................. 30 2.9 Special Weather Conditions ........................................................................................................ 30 Chapter 3 ENGINEERING AND TRAFFIC SURVEYS (E&TS) ...................................................................... 32 3.1 Overview ..................................................................................................................................... 32 3.1.1 Scope of Survey .................................................................................................................. 32 3.1.2 Components of an E&TS .................................................................................................... 32 3.2 Data Collection and Analysis ...................................................................................................... 32 3.2.1 Equipment ........................................................................................................................... 32 3.2.2 Location of Speed Measurements ....................................................................................... 33 3.2.3 Selecting Vehicles Under Free Flow Conditions ................................................................ 34 3.2.4 Measuring Vehicle Speeds .................................................................................................. 34 3.2.5 Recording Measured Speeds ............................................................................................... 35 3.2.6 Calculating 85th Percentile Speed........................................................................................ 35 3.2.7 Collision Analysis ............................................................................................................... 35 3.2.8 Evaluating Existing Conditions .........................................................................................