Off-road vehicles

Off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks. Other vehicles that do not travel public streets or highways are generally termed off-highway vehicles, including tractors, forklifts, cranes, backhoes, bulldozers, and Golf carts.

Off-road vehicles have an enthusiastic following because of their many uses and versatility. Several types of motorsports involve racing off-road vehicles. The three largest "4 wheel vehicle" off-road types of competitions are Rally, Desert Racing, and Rockcrawling. The three largest types of All Terrain Vehicle (ATV) / Motorcycle competitions are Motocross, Enduro, and also Desert Racing like Dakar Rallye and Baja 1000.  The most common use of these vehicles is for sight seeing in areas distant from pavement. The use of higher clearance and higher traction vehicles enables access on trails and forest roads that have rough and low traction surfaces.

Common off-road vehicles

Common commercial off-road vehicles include four wheel drive pickup trucks like the Ford F-Series, Chevy Silverado, GMC Sierra, Toyota Hilux, and Dodge Ram. In addition, light trucks with station wagon-like bodies, which have been very popular since the 1980s, are common. These include the Chevrolet Blazer, Dodge Ramcharger, FIAT Campagnola, Ford Bronco, Jeep Cherokee, Jeep Wrangler, International Scout, Mitsubishi Pajero, Isuzu Trooper, Rodeo Amigo, IVECO Massif, Land Rover Defender and Discovery, Mercedes-Benz G-Class, Suzuki Jimny/Samurai Suzuki Vitara/Sidekick/Grand Vitara, Range Rover, Nissan Patrol Xterra, Lada Niva, Toyota Land Cruiser and 4Runner. A number of those models have now become luxury SUV's with reduced off-road capability.

A number of military vehicles have also seen civilian use, including the Jeep CJ and the AM General Hummer. Some, like the early Land Rovers, were adapted to military use from civilian specifications.

Specialised commonly available off-road vehicles include ATVs (All Terrain Vehicles), dirt bikes, dune buggies, rock crawlers, and sandrails.

Commercial, military and less common off-road vehicles

European militaries and utilities have used Land Rover Defenders, Haflingers, Pinzgauers, Volvo L3314, and Mercedes-Benz Unimogs for all-terrain transportation. The Portuguese UMM Alter is less common.

The military market for off-road vehicles used to be large, but, since the fall of the Iron Curtain in the 1990s, it has dried up to some extent. The U.S. Jeep, developed during World War II, coined the word many people use for any type of light off-road vehicle. In the U.S., the Jeep's successor from the 1980s on was the AM General HMMWV. The Eastern Bloc used the GAZ-69 and UAZ-469 in similar roles.

Technical

To be able to drive off the pavement, off-road vehicles need several characteristics: They need to have a low ground pressure, so as not to sink into soft ground, they need ground clearance to not get hung up on obstacles, and they need to keep their wheels or tracks on the ground so as not to lose traction.

Wheeled vehicles accomplish this by having a suitable balance of large or additional tires combined with tall and flexible suspension.

Tracked vehicles accomplish this by having wide tracks and a flexible suspension on the road wheels.

The choice of wheels versus tracks are one of cost and suitability. A tracked drivetrain is more expensive and costly in terms of maintenance. Wheeled drivetrains are cheaper and give a higher top speed. For pure off-road capabilities, the tracked drivetrain has the edge.

Most off-road vehicles are fitted with especially low gearing. This allows the operator to make the most of the engine's available power while moving slowly through challenging terrain. A combustion engine coupled to a normal gearbox often has an output speed too high to be usable. The vehicle often has one of two things, either a very low ("granny") first gear (like the all wheel drive Volkswagen Transporter versions) or an additional gearbox in line with the first, called a reduction drive. Some vehicles, like the Bv206 in the picture on the right, also have torque converters to further reduce the gearing.

Many wheeled off-road vehicles have all wheel drive to keep traction on slippery surfaces; however, in vehicles designed for use both on and off road, this may be switchable so that the vehicle has fewer driven wheels when on the road.

Environment

In the United States, the number of ORV users since 1972 has climbed sevenfold—from five million to 36 million in 2000. Government policies that protect wilderness but also allow recreational ORV use have been the subject of some debate within the United States and other countries.

All trail and off-trail activities impact natural vegetation and wildlife, which can lead to erosion, invasive species, habitat loss, and ultimately species loss, decreasing an ecosystem's ability to maintain homeostasis. ORV's cause greater stress to the environment than foot traffic alone, and ORV operators who attempt to test their vehicles against natural obstacles can do significantly more damage then those who follow legal trails. Illegal use of off-road vehicles has been identified as a serious land management problem ranked with dumping garbage and other forms of vandalism. Many user organizations, such as Tread Lightly! and the Sierra Club, publish and encourage appropriate trail ethics.

ORVs have also been criticized for producing more pollution in areas that might normally have none. In addition to noise pollution that can cause hearing impairment and stress in wildlife, according to the U.S. Forest Service, old-style two-stroke engines (no longer a component of new off-road vehicles, although some are still in use) "emit about 20 to 33 percent of the consumed fuel through the exhaust" and "discharge from two-stroke snowmobile engines can lead to indirect pollutant deposition into the top layer of snow and subsequently into the associated surface and ground water. In 2002, the United States Environmental Protection Agency adopted emissions standards for all-terrain vehicles that "when fully implemented in 2012...are expected to prevent the release of more than two million tons of air pollution each year--the equivalent of removing the pollution from more than 32 million cars every year.
Tags: Game viewing vehicle , Sport utility vehicle , Ramp travel index , Tread Lightly! , Amphibious vehicle