This document was prepared by Karl A. Snyder, Ph.D., Agricultural Engineer, and Thomas G. Bobick, P.E., Safety Engineer, of the Division of Safety Research, National Institute for Occupational Safety and Health.

The authors would like to thank the many contributors who provided valuable assistance and suggestions during the preparation and editing of this handbook.

Ronald L. Stanevich, Acting Chief, Protective Technology Branch, Division of Safety Research, NIOSH, provided insight, long-term support and direction, and helped us to separate the grain from the chaff. Information on specific topics was provided by David L. Hard, Ph.D., Safety Specialist, Division of Safety Research, NIOSH; John A. Kramer, Extension Safety Specialist, Kansas State University; and Charles V. Schwab, Ph.D., Assistant Professor and Extension Safety Specialist, Iowa State University. Editorial, formatting, and document preparation assistance was provided by Linda L. Morton and Paul R. Keane, Writer-Editors, and Herbert I. Linn, Chief, Information Management and Dissemination Activity, Division of Safety Research, NIOSH. The artwork and document format were designed by Pavlina Vagoun-Gutierrez, Morgantown, West Virginia.