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.

September 23, 1999

Judson S. Ludeking
Contractors Risk Management, Inc.,
Post Office Box 211
Concord, New Hampshire 03302-0211

Dear Mr. Ludeking:

Thank you for your August 18, 1999 letter in which you described a hazard apparently not addressed by any specific OSHA standard, but which you believe might be cited by OSHA under the General Duty Clause of the Act. The hazard you described was that employees working at ground level in the vicinity of an operating aerial lift truck were exposed to possible injury as result of being struck by the personnel bucket when it is being lowered close to the ground.

In your letter you posed two related questions. In your first question you asked if OSHA would cite a company whose employees were exposed to this hazard. In your second question you inquired whether installation, on the aerial lift, of a device which would activate an audible alarm whenever the personnel bucket was being lowered, would "address the exposure sufficiently to eliminate any possible citations for the crushing exposure."

To your first question, the only answer I can offer is that OSHA might issue a citation for such an exposure if all necessary elements of a general duty clause violation were found to be present in a particular work citation. That is, the hazard could result in serious injury, sufficient industry or employer knowledge of the hazard was present, and the employer was aware that employees were exposed to the hazard. Since this hazard is not addressed by any specific OSHA standard or by the applicable industry consensus standard (ANSI A92.2), the determination of whether or not there is sufficient employer knowledge present to justify and support a citation for this hazard would necessarily be based on information, obtained during an OSHA inspection, that is specific to the particular employer and work situation. Consequently, the question of whether or not OSHA would issue a citation for this hazard must be decided on a case-by-case basis.

Regarding your second question, the installation of an audible device to warn employees that the bucket was being lowered would not, by itself, be viewed as acceptable abatement of the hazard. Since we know of no empirical evidence that installation of such a device would eliminate (or even reduce) the hazard, for the reasons that follow, we are not prepared to agree that it would.

As you pointed out in your letter, OSHA construction standards do accept a reverse signal alarm as an abatement method for protecting employees from the hazard presented by a rearward moving vehicle which has a restricted view to the rear. At first glance, it might seem that the situations are analogous, the difference being only horizontal versus vertical movement. But the situations differ in a way that is significant. In the case of the backing vehicle with a restricted view to the rear, it is not possible for the operator to see if a pedestrian employee is in the vehicle's path. Use of a spotter or reverse signal alarm may be the only feasible or practical means to reduce the hazard. The vehicle operator can not eliminate the hazard simply by backing the vehicle cautiously.

However, operators of an aerial lift bucket can look over the side of the bucket and see whether or not someone is working beneath them and close enough to be endangered by downward movement of the bucket. Therefore, it is our view that the most effective method for protecting employees from the hazard at issue is for the employer to ensure, through appropriate training and supervision, that aerial lift operators exercise the same caution when moving the bucket that is expected of them when they are moving the truck. That is, that they do not move the bucket unless they can see that it is safe to do so.

We should also point out some of the limitations of audible warning alarms. The effectiveness of audible alarms tends to diminish over time as workers get accustomed to the noise. We would expect this phenomena to be especially problematic in work situations where the employees are continually exposed to the alarm throughout their work shift, such as, when working next to a bucket truck, since they are normally stationary when the aerial bucket is in operation, and not moving in and out of the area as is often the case with vehicles equipped with conventional back-up alarms. We are aware of accidents wherein employees were seriously injured by backing vehicles which were equipped with functioning back-up alarms.

Beside the tendency of the human brain to temporarily tune out re-occurring noise, other factors that can result in workers not hearing an audible motion alarm include: a high ambient noise level (such as that resulting from the operation of chain saws and chippers next to the bucket truck), and the wearing of hearing protection. And, of course, some workers may already have a hearing impairment that could prevent them from hearing an audible motion alarm.

Another concern we have with reliance on an audible alarm is that employees operating the aerial bucket might conclude that the presence of this device obviates the need for them to look in the direction of movement before moving the bucket. We have seen where the installation of back-up alarms on equipment, such as fork trucks, when combined with inadequate training and supervision, can lead truck operators to assume pedestrian employees will get out of their way as soon as the back-up alarm sounds, and to begin moving the truck without first turning to look in the direction of travel.

We hope you find this responsive to your inquiry. Should you have any other questions concerning this matter, you are invited to contact Geoff McKinstry, Safety Specialist, at (617) 565-9893. We thank you for your interest in occupational safety and health.


Ruth McCully
Regional Administrator