Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at

May 20, 1991

Mr. Raymond W. Halsey
Colin Laboratories, Inc.
1470 Enterprise Parkway
Twinsburg, Ohio 44087

Dear Mr. Halsey:

This is in further response to your letter of March 16, which concerned a telephone conversation you had with Mr. Richard Sauger of our Office of Safety Standards Programs. Your concerns were whether or not the Occupational Safety and Health Administration (OSHA) Standard 29 CFR 1910.147 (lockout/tagout) would apply to motor vehicles.

Specifically, you posed the following question: If a truck driver or other person were to crawl under a truck, with the engine running, to adjust a linkage or fix another problem, would this be considered a violation of the standard? The answers is yes, this would constitute a hazard, as well as a violation. We would agree with the verbal opinion offered by Mr. Sauger that turning the engine off and removing the ignition key would deenergize and isolate the power source. The key would also have to be retained by the employee performing the maintenance operation in order to provide effective protection under the standard.

When servicing or maintenance activities are to take place, on any equipment, deenergization of that equipment will provide maximum safety to an employee. The removal of a vehicle key which can be kept in the sole control of the employee performing the maintenance or service can significantly reduce the risk of serious injury or even possibly a fatal injury.

We are enclosing a copy of the lockout/tagout standard for your use. We would point out the need to put into effect the other requirements of the standard, such a setting up an energy control procedure and employee training.

We hope this helps to clarify your concerns.

Your interest in workplace safety and health is appreciated.


Patricia K. Clark, Director
Directorate of Compliance Programs