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 https://www.osha.gov.

August 20, 1987

Mr. Robert Peyton, Director
Safety and Health Services
The Associated General
Contractors of America
1957 E Street, N.W.
Washington, D.C. 20006

Dear Mr. Peyton:

This is in response to your letter of July 24, concerning the problems associated with the definition, application and use of the term "Horns" as used in the 29 CFR 1926.602(a)(9)(i) section of the construction standard dealing with audible alarms.

29 CFR 1926.602(a)(9)(i) requires all bi-directional machines, such as rollers, compactors, front-end loaders, bulldozers, and similar equipment, shall be equipped with a horn, distinguishable from the surrounding noise level, which shall be operated as needed when the machine is moving in either direction. The horn shall be maintained in an operative condition.

This Agency believes that the requirement of a horn on the above mentioned equipment provides an increase measure of protection for employees exposed to the movement of the machine and the work being performed by the operator of the equipment. The operator can sound the horn to warn exposed employees of any impending hazards without having to dismount or leave machine controls.

In regards to our requirement for a reverse signal alarm, The Associated General Contractors of America, Inc. Manual of Accident Prevention in Construction Sixth Revised Edition (1971) in Chapter 18-7 provides the General Safety rule as follows:

Heavy earthmoving equipment should be equipped with a reverse signal alarm which will operate automatically with backward movement. The alarm should give an audible signal suitable for the conditions. The signal may be continuous or intermittent, but should provide suitable alarm during the entire time of backward movement.

The National Institute of Occupational Safety and Health in its Health and Safety Guide for Highway and Street Construction (Publication No. 78-196 provides guidance as follows:

Audio Alarms

A horn, distinguishable form the surround noise level, shall be provided and operated as needed on all bi-directional machines such as rollers, compactors, front-end loaders, bulldozers, etc.

A reverse signal alarm or a signalman shall be provided for all earth moving or compacting equipment which has an obstructed view to the rear.

The United States Department of the Interior Construction Safety Standards (1978) requires as follows:

Audible alarms. All mobile equipment shall be equipped with a horn distinguishable from the surrounding noise level and an automatic back-up alarm.

The above mentioned regulations support our standard requiring reverse signal alarms or allowing an employee to signal that it is safe to back-up.

If we can be of further assistance, please let us know.


Thomas J. Shepich, Director
Directorate of Compliance Programs