d Div. 100 ! i I 1 ' L BS BUILDING SCIENCE SERIES 108 afety on Stairs S DEPARTMENT OF COMMERCE • NATIONAL BUREAU OF STANDARDS NATIONAL BUREAU OF STANDARDS The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote pubUc safety. The Bureau's technical work is performed by the National Measurement Laboratory, the National Engineering Laboratory, and the Institute for Computer Sciences and Technology. THE NATIONAL MEASUREMENT LABORATORY provides the national system of physical and chemical and materials measurement; coordinates the system with measurement systems of other nations and furnishes essential services leading to accurate and uniform physical and chemical measurement throughout the Nation's scientific community, industry, and commerce; conducts materials research leading to improved methods of measurement, standards, and data on the properties of materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government Agencies; develops, produces, and distributes Standard Reference Materials; and provides calibration services. The Laboratory consists of the following centers: Absolute Physical Quantities^ — Radiation Research — Thermodynamics and Molecular Science — Analytical Chemistry — Materials Science. THE NATIONAL ENGINEERING LABORATORY provides technology and technical services to users in the public and private sectors to address national needs and to solve national problems in the public interest; conducts research in engineering and applied science in support of objectives in these efforts; builds and maintains competence in the necessary disciplines required to carry out this research and technical service; develops engineering data and measurement capabilities; provides engineering measurement traceability services; develops test methods and proposes engineering standards and code changes; develops and proposes new engineering practices; and develops and improves mechanisms to transfer results of its research to the utlimate user. The Laboratory consists of the following centers: Applied Mathematics — Electronics and Electrical Engineering^ — Mechanical Engineering and Process Technology^ — Building Technology — Fire Research — Consumer Product Technology — Field Methods. THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides scientific and technical services to aid Federal Agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal Agencies; and provides the technical foundation for computer-related policies of the Federal Government. The Institute consists of the following divisions: Systems and Software — Computer Systems Engineering — Information Technology. 'Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234. ^Some divisions within the center are located at Boulder, Colorado, 80303. The National Bureau of Standards was reorganized, effective April 9, 1978. NBS BUILDING SCIENCE SERIES 108 Safety on Stairs D. H. Carsoni J. C. Archea^ S. T. Margulis^ F. E. Carsoni ^Carson Consultants, Inc. Milwaukee, Wisconsin 53701 ^College of Architecture Georgia Institute of Technology Atlanta, Georgia 30332 ^Center for Building Technology National Engineering Laboratory National Bureau of Standards Washington, DC 20234 Sponsored by Consumer Product Safety Commission 5401 Westbard Avenue Bethesda, Maryland 20207 U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary Dr. Sidney Harman, Under Secretary Jordan J. Baruch, Assistant Secretary for Science and Technology NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director Issued November 1978 . Library of Congress Catalog Card Number: 78-600036 National Bureau of Standards Building Series 108 Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 108, 122 pages (Nov. 1978) CODEN: BSSNBV U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1978 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20234 SD Catalog Stock No. 003-003-02026-5 Price $3.00 (Add 25 percent additional for other than U.S. mailing) ABSTRACT Stairways are commonplace in U.S. homes. Stairway design and construction standards are based on custom, common sense, and experience. Stairways, however, are hazardous. A large number of stairway accidents have been reported, raising questions about the adequacy of stairway design and construction standards. This study is a first attempt to rationalize stairway standards by ap- plying well established statistical methods to a significant sample of stairways and people using them. A pilot study on a sample of 253 residences in Milwaukee County, Wisconsin, was undertaken. The study included a survey of stairway use and behavior and an inventory of residential stair- ways. This information was obtained from the total sample. In a subsample of 54 residences, direct field observations and physical measurements of stairways were obtained. The results of the pilot study include a description of existing stairways, inference about interactions that pro- duce accidents, and guidelines which address reasons for accidents (hence should result in a reduc- tion of accidents). The best strategy for making stairways safer, according to the study, is to re- move factors that influence accident rates. Specifically, by systematically reducing hazards, care- less stairway habits, and frequency of use, patterns of factors responsible for accidents can be broken and accident rates can be reduced. Key words: Accidents; architectu'-al psychology; consumer products; environmental factors; home safety; occupant behavior; survey technique. iii CONVERSION FACTORS TO METRIC (SI) UNITS Quantity To convert from To Multiply by Length inch m (meter) 2.540x10-2 foot m 3.048x10-1 mile m 1.609x103 Area in2 m2 6.452x10-4 2 ft2 m2 9.290x10 Volume in^ m^ 1.639x10 5 2 ft3 m^ 2.832x10 gallon m^ 3.785x10 3 Temperature °F °C toe = (toF-32)/1.8 T. difference At=F K ATK=AtoF/1.8 Mass pound kg 4.536x10-1 ounce kg 2.835x10-2 Pressure psi Pa 6.895x103 in HjO Pa 2.488x102 in Hg Pa 3.386x103 mmHg Pa 1.333x102 Energy Btu J 1.055x103 MBtu J 1.055 xlO^ kWh J 3.600x10^ ft-lbf J 1.356x10" kilocalorie J- 4.184x103 Power Btu/h W 2.931x10-1 hp W 7.457x102 Flow gal/min m^/s 6.309x10-5 ft^/min m^/s 4.719x10-* Density lb/ft3 kg/m^ 1.602x101 lb/gal ke/m^ 1.198x102 Heat Capacity Btu/(lb-°F) J/(kg-K) 4.187x103 Btu/(ft3-°F) J/(m3-K) 6.707x10^ iv CONTENTS page LIST OF TABLES AND FIGURES vii ACKNOWLEDGMENTS x PREFATORY REMARKS xi 1. SUMMARY AND GUIDELINES 1 1.1 Introduction 1 1.2 Background and Setting of the Study 2 1.3 Scope 3 1.4 Summary of Physical Inventory 3 1.5 Summary of User Survey 4 1.6 Summary of Influences on Frequency of Stairway Use 5 1.7 Summary of Accident Analysis 5 1.8 General Observations from Site Visits 10 1.9 Eighteen Guidelines for Improved Stair Safety 11 2. DESCRIPTION OF STAIRWAY STUDY 15 2.1 Introduction 15 2.2 Sampling Plan and Overall Study Design 17 2.3 Demographic Comparisons 17 2.4 Data Collection Methods 18 2.5 Survey Procedures 19 2.6 Types of Data Collected 19 2.6.1 Demographic and Background 19 2.6.2 Physical Inventory 19 2.6.3 Behavioral Survey 19 2.6.4 Site Measurements 20 2.7 Definitions and Restrictions 20 2.8 Definitions Relating to Accidents 20 2.8.1 Severity 20 2.9 Note on Data Analysis and Inferences 21 3. PHYSICAL INVENTORY OF STAIRWAYS 23 3.1 Note on Terminology 23 3.2 Number of Stairways Studied and Their Structural Materials 24 3.3 Tread Material on Inside Stairways 24 3.4 Riser and Tread Measurements: Irregularities and Dimensions 27 3.5 Handrail Measurements: Height, Width, Variation and Rigidity 28 3.6 Stairway Length: Number of Risers by Stairway and Flight 29 3.7 Lighting Levels and Gradients: Light Switch Locations 30 V 3.8 Low Headroom and Orientation Edges 31 3.9 Stairway Configurations as Related to Age, Type of Structure 32 4. BEHAVIORAL SURVEY OF STAIRWAY USE 35 4.1 Intended Stairway Repairs 35 4.2 Respondents' Recommendations for Improving Stairway Safety 35 4.3 Stairway Habits Related to Accidents 38 4.4 Assessment of Safety: Percent Safe 39 4.5 Frequency of Stairway Use 39 4.6 Home Activities, Housing Preference and Potential Sources of Home Accidents ... 41 4.6.1 Home Activities 41 4.6.2 Housing Preferences 41 4.6.3 Potential Sources of Home Accidents 41 5. MEASUREMENT AND ANALYSIS OF STAIRWAY HAZARD 43 5.1 A Measure of Stairway Hazard 43 5.2 Stairway Use Related to Physical Variables 45 5.3 Stairway Use Related to Personal Variables 45 6. ANALYSIS OF ACCIDENTS AND CRITICAL INCIDENTS 47 6.1 Note on Accident Analysis 47 6.2 Comparison with NEISS Accident Data