Brush trucks are custom vehicles fire fighters can take off-road
Last year, more than 10 million acres of land burned in the United States, and much of that wasn’t easily accessible by road, much less urban infrastructure like fire hydrants. Fighting fires on rugged terrain adds complicates the logistics of an an already difficult job, since many of the vehicles and systems a fire department can use in a city, like ladder or pumper truck, will have a difficult time reaching the front lines of a fire in the woods, if they’d even be useful in that environment in the first place. To deal with this, fire fighters have employ more exotic equipment, like helicopter buckets or bulldozers to make firebreaks. The most versatile vehicle though is the wildland fire engine, also known as a brush truck.
Brush trucks are basically the trucks a fire fighter can take off road, into the brush and brambles where a fire’s front line is likely to be. Since they might be one of the few vehicles that can gain access to areas with steep grades or rough terrain, these trucks are often equipped with tools, medical supplies and some amount of water to spray at a fire. The flexibility of a brush truck’s payload is actually part of its origins, as they were originally built from other, off-road-capable vehicles, such as those obtained as military surplus. They were then customized to fit a specific fire department’s needs, or possibly just capabilities depending on the equipment available. While you can now buy a brush truck new, the idea that they are customizable is still key to their design.
Also appropriate for urban jungles
Even though large ladder trucks designed to help with burning skyscrapers aren’t practical on mountain roads, some brush trucks have found their way back to cities. The shorter chassis allows these smaller vehicles to maneuver through traffic more easily than a large fire engine, which can save critical time for first responders. The trucks can also bring equipment and small water pumps to cramped urban spaces, such as multi-level parking lots, to deal with things like medical emergencies or car fires. While fire departments in the wilderness and in cities obviously still need their more specialized equipment, brush trucks make a good case for the value of versatility as well.
Source: What is a Brush Truck?, wise Geek