Getting the Most Out of Forklift Alarms
Backup alarms must be treated more creatively than the same application in other industrial equipment.
- By Barrett Miller
- Sep 01, 2003
BACKUP alarms are installed on forklift trucks because they provide notice to a worker that a forklift is in close or immediate proximity. If they worked perfectly--and they don't--they might prevent as many as 20 deaths per year from pedestrian-forklift accidents and reduce injuries by seven thousand1 or more.
Forklift alarms cannot be used in every situation, but given careful analysis, the device can reduce management costs without the need to rely exclusively on the operator to sound the horn or the supervisor to supervise the operator. In the best sense, backup alarms can help make up for the human shortcomings of operators, supervisors, and pedestrians.
If the ambient sound level in an area is too great or the physical dimension of the work site is too small, forklift alarms are ineffective. In every case, it is important to use additional intelligent management practices like assigning spotters, establishing workstation isolation, and setting restrictive corridors that are protected from moving vehicles.
Manufacturers of forklift trucks see backup alarms as a controversial subject. OSHA never has made a commitment to enforce the installation of alarms on forklifts, but if the vehicle was manufactured with an alarm, rearview mirror, or other safety device, the employer may be cited for a failure to maintain safety equipment. Some believe OSHA has no authority to force performance that goes beyond the strict wording of a national consensus standard.2 That may be true. ANSI B56.1 says:
4.1.2. Unusual operating conditions may require additional safety precautions and operating instructions.
4.15.2. The user shall determine if operating conditions require the truck to be equipped with additional sound-producing or visual (such as lights or blinkers) devices, and be responsible for providing and maintaining such devices.
Historically, the forklift industry fought mandatory requirements for alarms as well as seat belts and rear-view mirrors. Manufacturers assert that forklift alarms should be regulated solely under the guidelines of a national consensus standard, in this case ANSI B56.1.
Membership of the B56 committee is controlled by the forklift industry association. There is nothing insidious in this, but as long as this standard is regulated by a captive committee, forklift alarms will remain optional and not a regulated duty. One manufacturer in particular has actively opposed the use of backup alarms and rear-view mirrors, which they think diminish safety in the workplace. This company's literature hasn't changed a single word on the subject in more than 15 years. It also opposes the use of warning or strobe lights. We urge readers to evaluate the opinion of this manufacturer,3 which cites:
- Excessive noise level exposure to the operator resulting in annoyance, fatigue, and long-term hearing loss.
- Pedestrians become habituated to the alarm and ignore it, because it constantly sounds a meaningless warning.
- Operator depends on alarm to clear pedestrians from path, rather than looking in direction of travel.
- Multiple alarms due to more than one lift truck cause confusion and increased workplace noise.
- Disconnection or disablement by operators.
OSHA continues to recommend backup alarms on forklifts but has limited enforcement power. This leaves OSHA relying on other more traditional responses such as barrier islands, segregated forklift routes, and secured workstation design.4
The most important actor in this safety paradigm is the field supervisor. However, the installation and use of alarms is increasing, fueled by state codes and industry demand.5 Why, one might wonder, would an employer want to add an expensive piece of equipment when there is no strict legal requirement? It is because, to the extent an alarm is effective, users are free from the cost of maintaining a spotter.
California's industrial commission is a representative example of state enforcement. In response to my inquiry, they said: The Cal/OSHA Regulations do not specifically require alarms on forklift trucks; however, Section 1592(a)&(b) of the Construction Safety Orders requires alarms on vehicles that meet the conditions therein. Section 3656(c) of the General Industry Safety Orders(GISO) requires a flashing or rotating light on Order Pickers and Stock Pickers, and 3664(a)(11) of the GISO requires the use of a horn by industrial trucks and tow tractors.6
Manufacturers of all products share a common duty, independent of code or statute. The obligation to release one's product into a marketplace in a manner responsive to public safety extends beyond federal statute or code.7 Compliance with a known code does not create a legal presumption that the product is safe. As you can imagine, this has led itself to mountains of litigation. In litigation, manufacturers' public defenses restate the obvious. Their behavior is dictated by the American National Standard. Another voluntary code, SAE J994--a surface vehicle standard--is often used to beg compliance by those who choose to manufacture their vehicles with alarms. This standard is a general-industry practice and does not address unique forklift requirements.8
The Electric Laboratory Performance Testing Standard for general equipment alarms is adequate for production levels in most industry equipment and confronts most of the important operating conditions an average industrial truck will encounter. However, it does not pretend to be able to match the backup alarm to any unique set of workplace conditions. The standard specifies alarm frequency and timing, as well as the even distribution of sound. One critical test is for the masking characteristics of sound in response to engine noise.9 The standard measures device sensitivity to heat, weather, and voltage changes. The standard ignores the issue of alarm placement on forklifts and does not provide a means of determining how one evaluates the ability to alert a pedestrian in the presence of an already elevated sound level.
While it is common to rely on general-purpose standards where no specific product standard exists, safety is not always served. SAE J994 actually may create test conditions that are not compatible with safe forklift operations. Forklifts' alarms are needed at a specific distance corresponding to warning response and ideally would be reduced in other directions. If one designs and places a backup alarm specifically for a directional pattern, allowing the pedestrian four seconds to respond, it may be possible with proper application to reduce overall environmental sound levels.
No one has addressed the application of alarm frequency patterns in response to the types of ambient sounds. This could be completed by the manufacturers, but only major consumers would have the capacity to do this work for themselves.
The Physics of Sound
The author once investigated the behavior of a captain during the sinking of a large yacht. A small salon area housed almost 100 alarm functions on three panels. Three alarm attenuators set at 110 dBA were used to alert the captain, who stood three feet away.
The alarm was located in the salon, an area of about 100 square feet. The salon was reflective, and the sound level continued to bounce back and forth across the space. Another siren was mounted on the fly bridge and broadcast its signal across the ocean; another was on the rear observation deck.
I questioned whether a person could respond to the three signals and concluded that the alarms produced confusion. From the captain's position, I measured 95 dBA in an area that normally maintained a sound level no more than 40 dBA. When I replicated the alarm on a similar yacht, I found that after a minute in close proximity to the 95 dBA attenuator, I could not think clearly and became nauseated. When I walked toward the rear deck, I could hear two other alarms. Because of the distance and their unique surroundings they seemed quieter, and they appeared to be alerting me to different conditions for which I could not account.
Sound waves are nothing but changes in pressure caused by vibration at a distant point. Measurements are made in reference to a straight linear path. The pressure change that reaches your ear is interpreted by the brain as sound. Frequency is dependent on the character of the original source. Sound waves at a given point are not the same air or vibration that existed at the original source. As sound travels, it spreads and becomes weaker and as it pushes succeeding air volumes. Sound diminishes inversely proportional to distance. Sound changes in response to a number of things.
If the frequency and direction of blending sound waves are the same, the gross volume of sound will increase. But when sounds collide and have a different frequency, they blend and cause a sound pressure different from the original but sharing certain characteristics. To illustrate, think of the way an orchestra's sounds blend. The tuba, the violin, and the drum combine to produce a sound substantially different from that of any individual source. The instruments may or may not create a greater sound level, depending on phase and direction. In industrial settings, when the blend of sounds is unwanted, unpleasant, and destructive, we call the resultant sound noise.
Sound is measured in decibels. A doubling of sound produces a measured reading of 3 dBA. In laboratory conditions, one can barely recognize a change of 6 dBA.10 You might decide to measure the sound level from any given point to your listening position. You also may compute the level of sound mathematically if you know the level and distance of the sound at another point.11 Blending sound sources may be louder, softer, or the same. The only certainty is that the resulting sounds will be different but will share original characteristics.
Backup alarms on forklift trucks must be treated more creatively than the same application in other industrial equipment. With a forklift, for example, there is an optimum distance and direction at which the target listener should hear the alarm. That distance should be approximately four seconds travel time using the customary speed in any given work site.
Settings should vary with individual job sites and other sound sources present. A good rule of thumb is that to be heard, a backup alarm must be about 10 dBA higher than the ambient sound level. At the same time, working volumes should stay below the action levels established in time weighted averages. As a rule, the maximum periodic sound from a backup alarm at 25 feet should be no more than 80 dBA.12
It may be necessary to change the frequency range of the alarm to provide control the way sounds blend with other noises. It makes no sense to use an alarm that is too loud. Don't use an 80 dBA alarm in a working environment where the average sound level is 40 dBA, for example. This goes beyond the customary duties for most manufacturers, but in most situations, they are the most qualified to do the study and make suitable recommendations.
Research on Backup Alarms
Most research on backup alarms relates to sound level. However, four things can be manipulated to improve their effectiveness. We can evaluate the tonal range of the alarm or establish new rules for the placement of the alarms. On first examination, placing the alarm at a higher level and focusing of the direction of the sound wave seem to be highly productive ideas. Potentially, the sound can be directed to reach only the desired listener without sending unwanted tones randomly throughout the workplace.13
Consensus standards show the common belief that a backup alarm must be louder by a factor of at least 10 dBA. It seems reasonable to assume that if several forklift trucks operating in the same area will increase sound levels by 10 dBA for the entire work site, occasionally by a larger amount, in noisy environments this is impractical. The use of self-adjusting backup alarms that sense the ambient noise in an area and then automatically self-adjust to 10 decibels higher than that level can potentially improve both the directionality and overall sound level in the work site, and limit sound pollution.
New devices called Pre Backup Ground Personnel Alerting Devices14 may be used with or without a continuous sound or light system. The OSHA Directorate of Construction reviewed this device in 1993 and found the device meets the intent of codes requiring backup alarms.15 Accident prevention is achieved by warning the driver of a vehicle before the collision takes place. The concept is simple; the operator of a vehicle will avoid the accident if he/she knows the potential of a collision exists. As the vehicle backs toward an obstacle, the radar pattern is interrupted and detection is made. Upon detection, the driver's buzzer/light device is activated in the cab to provide an adequate warning.
It might be useful to think of these devices as providing alert, but not alarm. To be effective, backup alarms should focus the direction of the sound wave into a zone where it will be most useful. At no time should a manager allow the alarm to increase the ambient sound level in a way that increases the 85 dBA action level for sounds in the workplace, unless the entire audible environment has been evaluated. The output level of the forklift alarm should be about 10 decibels above the average sound level in the area. This approach, along with alarm devices that choose the level of output, can reduce the nuisance level of alarms.
Modern alternatives have been accepted by OSHA for more than 10 years, but forklift manufacturers do not use them. It is now possible to provide continuous alarms, alarms that activate only in the presence of a pedestrian, and alarms that--while continuous--increase sound in the presence of the pedestrian. While the alarm sends notice to the person on foot, the existence of a pedestrian sends no notice to the forklift driver. That has changed. This is especially important because forklifts are required to operate in reverse while carrying loads. Many have a great many blind spots.
The use of backup alarms is now more common. This is caused, in part, by statutes for other applications. It is also because forklifts are more frequently considered multi-use vehicles, and many sympathetic uses require alarms. New research and new products offer promise but have not been widely accepted.
Twenty or more lives can be saved each year if forklift alarm technology is improved. Many of the 7,000 annual injuries in forklift/ pedestrian accidents can be prevented, but it appears only changes in administrative codes can force change. In most cases, the expertise and equipment to design the sound environment are under the control of manufacturers and their dealers.
1. NIOSH Alert, "Preventing injuries and deaths of workers who operate near forklifts." Publication 2000-112, December 1999 (www.cdc.gov/niosh/2000-112.html).
2. OSHA doesn't require but recommends--Alarm guidelines, July 28, 1987.
3. Toyota marketing brochure, "optional equipment."
4. Case studies establishing response to material handling accidents, found in guidelines for the maritime industry (OSHA Abatement Summaries, January 2003).
5. Hazard Alert Bulletin: Forklift fatalities. New Jersey Department of Health and Senior Services, December 1998.
6. Formal Inquiry, Feb. 7, 2003.
7. Clark v. Chrysler Corp., F.3d (WL 2002, WL 31386161).
8. Society of Automotive Engineers standard J994, Surface vehicle standard.
9. The measurement of the blending character of the engine alarm is restricted to the emissions control function commonly called high idle.
10. This follows the scientific doctrine of "Least Perceptible Change."
11. The Inverse Square Law for waves.
12. 85 dBA is the OSHA action level for hearing protection. At that level, the employer is required to initiate a hearing preservation program.
13. Vermont sets goal of 50-55 dBA for construction sites.
14. R.F. Knapp Co., www.rfknappco.com/Radar_System/system_202.htm.
15. Advisory letter from OSHA Office of Construction and Maritime, July 12, 1993.
This article originally appeared in the September 2003 issue of Occupational Health & Safety.