vii FOREWORD “Develop a comprehensive medical oversight program for interstate commercial drivers….” Thus begins a Safety Recommendation issued to the Federal Motor Carrier Safety Administration (FMCSA) by the National Transportation Safety Board (NTSB) in 2001 in response to “serious flaws” in the medical certification process for commercial drivers. The FMCSA has made halting progress toward this goal, but Dr. Natalie Hartenbaum continues to edit the single most important source of guidance for those commercial driver medical examiners who would make transportation safety their highest priority. As the FMCSA works to transition toward a more systematic process for commercial driver medical evaluation, it is even more important that those performing the exams have a ready reference for the often-complex questions they will need to address. The FMCSA’s process clearly lays responsibility for the consistent performance of commercial driver certification examinations at the foot of the certi- fied examiner. This book fills the gaps between what such examiners are obligated to do by their position and what will best provide for highway safety. The book has always served as a concise collection of the critical regulatory and guidance information on the process of the examination, specific data-driven recommendations on how to perform and evaluate various portions of the exam itself, and straight- forward acknowledgment of where the science or directives (or both) may fall short. The first edition of this book was published at about the same time that I was beginning my tenure as the Medical Officer at the NTSB, and I have come to know Natalie as a passionate and tireless advocate for transportation safety. She has taught for over two decades on the commercial driver examination process, edited the American College of Occupational and Environmental Medicine (ACOEM) Commer- cial Driver Medical Examiner Review for over 15 years, served as the ACOEM Transportation Section Chair for more than 10 years, and is a past president of ACOEM. She brings to this edition of The DOT