A mobile elevating work platform, is an engineering control that can reduce the risk of musculoskeletal disorders from overhead work. These mechanical devices can provide temporary access to elevated work sites and may be manually-propelled (push-around), self-propelled (drivable), or vehicle-mounted. They can mechanically function in two different ways such that some can usually only elevate vertically (i.e. scissor lifts) whereas some are situated on an articulating arm that can also allow horizontal movements (i.e. boom lifts).

Aerial work platforms can mechanically function in two different ways and are categorized as either "scissor" lifts or "boom" lifts. Scissor lifts usually have work platforms that can only elevate vertically whereas boom lifts have work platforms situated on an articulating arm that can also allow horizontal movements. 

Some may be more suitable than others in certain work conditions and environments. Further, there are also different types of aerial work platforms. This list generally includes:

Manually-propelled

These are the typical push-around aerial platforms since they are not capable of moving under their own power.  Usually, these are one-occupant vertical lifts (scissor lifts) commonly called "Genies," although there are other manufacturers that make them.  In some cases, boom lifts can also fall under the manually propelled type such as a trailer-mounted AWP.

(Photo courtesy of Terex Corporation)

Self-propelled

These are driveable lifts in which operators (workers) can operate while the job is in progress.  This type of MEWP also covers both scissor and boom lifts.

(Photo courtesy of Terex Corporation)

Vehicle-mounted

This type of MEWP covers articulating boom lifts, which are usually mounted on a vehicle.

 

(Photo courtesy of Terex Corporation)

MEWP provide a large, mobile, guarded and stable work area that can usually be occupied by more than one worker. Boom lifts can elevate a worker into positions that would be difficult to reach safely using a ladder. The use of lifts may eliminate the erection of stationary scaffolding or repeated movement of ladders.

Although an MEWP may serve as safer alternative to ladders and scaffolds, these must be carefully selected to match the work being performed and must be maintained and operated in strict conformity with the manufacturer's manual and with OSHA and ANSI standards.

Users must ensure that:

• The equipment that they buy, lease, rent or borrow is built and maintained in accordance with OSHA and ANSI requirements
• The operator of the AWP is trained by a qualified person before being assigned to operate the aerial platform
• The operator is familiarized with the aerial platform to be operated
• The operator is retrained, if necessary, based on the user’s observation and evaluation of the operator
• Each piece of equipment is provided with an operation and maintenance manual that is maintained on that piece of equipment; usually in a weather resistant compartment (not in the office)

Operators must:

• Be trained by a qualified person before operating any lift
• Read, understand and follow the manufacture's operating instructions for the specific piece of equipment being used
• Read all decals, warning and instructions on the work platform
• Conduct a work area inspection prior to using each lift
• Conduct a thorough equipment check for defects such as cracked welds, hydraulic leaks, damaged  control cables, loose wire connections and tire damage, and inspect functional controls for proper operation prior to work on a daily basis
• Operate the AWP within the safe limits as specified by the manufacturer and ensure that any provided stabilizing devices, such as outriggers, are used in accordance with the manufacturer's instructions
• Guardrails are kept completely in place, including entry opening chains or gates
• Properly wear and attach fall arrest systems (workers on guarded scissor lifts are not required to use personal fall arrest systems unless they leave the lift's guarded area)

Before each elevation the operator must check:

• For overhead obstructions and high-voltage conductors. A minimum of ten feet must be maintained at all times between any conductor and the operator and work platform.  It is recommended that this distance be marked on the ground to aide operators.
• That the platform is elevated only on a firm and level surface (unless the equipment is specifically designed for unlevel surfaces, in which case the manufacturer's directions must be strictly followed).
• That the load is configured on the platform in conformance with the manufacturer's recommended load limits
• That any required outriggers or stabilizers are deployed
• That guardrails are installed and that entry gates or chains are securely closed
• For boom and bucket trucks, that all occupants are wearing properly attached full-body harnesses

While driving the elevating work platform (under the conditions specified by the manufacturer) the operator must:

• Look in the direction of travel
• Ensure that the path is clear, firm, and level
• Maintain a safe distance from obstacles, drop-offs, holes, personnel and other hazards.
• Maintain a safe distance from overhead obstacles
• Maintain a safe speed

Safe operation includes steps to prevent the tip-overs, falls, electrocutions and crushing injuries that result in about 26 construction worker deaths each year. Users must ensure that operators are trained by a qualified person, and must understand and adhere to all requirements of the manufacturer's operations manual.
 

Tip-Over Prevention

Scissor lifts, like other scaffolds, must be maintained in a level and plumb configuration.  Indoor or "slab" machines are required by ANSI to be tested for stability at 5 degrees greater slope than the machine is rated for. Manufacturers, however, usually treat this as a safety margin and clearly mark the equipment for use on level surfaces only. These lifts must not be used on uneven surfaces or where they may be driven into holes or depressions greater that 4 inches.  Scissor lifts specifically designed for rough terrain are available.  Any outrigger or stabilizing device provided by the manufacturer must be used in strict compliance with the operations manual. No exceptions may be made for brief jobs.

Fall Prevention 

Either a guardrail or a personal fall arrest system must be used by workers on a scissor lift. A properly maintained and closed guardrail system best serves this purpose. Attachment points may be provided for lanyards, but should only be used for fall restraint since fall arrest could cause the lift to tip over if the lift has not been specifically designed to accommodate the resultant force. Although a body belt may be used for a fall restraint (not fall arrest) system, it is a better practice to use a full body harness.

A fall arrest system may be required if the worker exits the guarded area of the scissor lift. In that case the lanyard must be attached to a suitable exterior attachment point, not to the guardrail.  Workers must not be attached to an external anchorage point while working on the lift. Workers in an aerial lift (boom or bucket truck) MUST be protected by both a guardrail and a fall arrest system. 

Using a railing, ladder, planks or any other devise for gaining additional height is not permitted on any elevated work platform. Workers must maintain a firm footing on the platform at all times, except for workers on a scissor lift who are wearing a fall arrest system attached to an external anchorage point while exiting the guarded area of the lift, or who are attached to a manufacturer approved hardpoint.

Boom lifts are not designed to elevate materials and may collapse or tip over under excessive loads.  Always use a crane or telehandler to raise materials.

Scissor lifts should not be operated in high winds, especially if materials that may act as sails are on the lift.

All-terrain fork-lifts require specialized operator training that meets OSHA requirements for fork lift operators.  This training is different that that usually provided to aerial lift operators.

Jean Christophe Le, MPH. - CPWR - The Center for Construction Research and Training.