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Terrain's influence on features
OSHA regulations require general contractors to provide surface conditions that enable easy site access, Roeske comments. "But sometimes you do have dirt conditions mixed with gravel, and you have Mother Nature to deal with," he says.

Consequently, Roeske almost always specs four-wheel drive on boom lifts. "We work 12 months out of the year, whether it's cold or hot, wet or dry," he points out. "Four-wheel drive is normally a very valuable asset."

Four-wheel drive has become almost standard on models for outdoor use. "Most of the combustion-powered machines we sell are four-wheel drive with an oscillating axle," says Mohn. "That's what people generally want, I think as much for the versatility — because they never know what kind of job they're going to run into — as for the resale value. A four-wheel drive is going to bring more when you go to sell the machine than a two-wheel drive."

Gradeability is another consideration if the lift will be driven over slopes. However, Mohn suggests taking this a step further to assess "terrainability" of the lift. "How does it get around the jobsite? If one tire starts to spin, are you going to be stuck? Do you have the proper flow division to transfer the power to the wheels to still have traction to pull you through?" he asks. "To us, that's more important than a straight gradeability number — whether you can get around the jobsite in different types of conditions."

Ground conditions influence the type of tires required, as well. Indoor applications may require non-marking tires, while sensitive landscape, such as a golf course, may dictate turf tires. Areas such as South Florida, where sugar sand is prevalent, may call for high-flotation, non-aggressive sand tires, or even tracks.