|Preparation and Operation of Off-Highway
Vehicles for Search and Rescue
Just as a golfer doesn't develop a proper swing or a tennis player doesn't develop a good backhand just by reading books, a driver must diligently practice the techniques of proper off-highway driving to develop skill and judgment. This article provides an introduction to the preparation and knowledge portions of the off-highway equation. While the primary emphasis is on the operation of four-wheel drive vehicles, the information can also be applied to two-wheel drive utility vehicles. Readers are strongly encouraged to consult the recommended bibliography at the end of this article for excellent, expert advice in considerably more detail, particularly the Tread Lightly! booklets and Crow and Murray (1986).
SAR teams should be aware of four-wheel drive organizations in their areas. These resources can be valuable, particularly in truly treacherous terrain. It can be very helpful to have a driver experienced with the specific terrain as an advisor or leader, just as it is helpful to use the knowledge of an expert climber who has personal experience in an area where a technical rescue is required. In many ways, expert four-wheel driving has much in common with technical climbing.
* What is the terrain like in your area? Is it steep and rocky, with narrow roads and lots of snow in the wintertime? Is it hot, sandy desert country?
* What about the weather? Is it dry, or is deep mud or snow often a problem?
* Do you search for lost hunters who are thought to be somewhere within a 100-square mile area, using your vehicles to cover all existing roads and trails?
* Are you looking for lost hikers in a wilderness area, ferrying ground search teams to trailheads at the wilderness boundary?
* Are you looking for hard-core four-wheelers who are overdue?
Each of these scenarios will have an effect on your preparations. The key is to make a realistic list of your anticipated mission needs and expected conditions, then plan which preparations will best fulfill your unique needs.
Preparation of an off-highway vehicle for serious use begins with maintenance. Always be sure that your vehicle is in top condition. Perform factory recommended service more often than required, particularly lubricating the chassis and drivetrain. Check the belts and hoses before every mission. Always clean the vehicle thoroughly after every off-highway trip to remove any mud, dirt or salt that can cause corrosion problems.
Tires can make a drastic difference in a vehicle's ability to travel the back country. There are three major variables to consider when selecting tires: rolling diameter, width and tread pattern. Ruggedness of construction and availability are also important.
Taller tires will increase ground clearance, but at a price. Taller tires change your vehicle's gear ratio, effectively robbing it of power and reducing its ability to crawl at low speeds. Tall tires can also interfere with fender openings and worsen the vehicle's turning radius, requiring a lift kit. A moderate increase in tire diameter of one to two inches over standard, or "stock," is usually okay, but larger increases will probably require gearing changes and/or lift kits.
Wide tires certainly look cool, and they work very well in sand, bottomless mud and deep snow. However, a narrower tire works better in rocky terrain and in shallower mud and snow with a firm bottom. The tire width you select is one of those factors that will be determined by the prevalent terrain in your area. If you are located in the mountains, you should use a relatively narrow tire-standard or a little wider. If you are based in the desert, you may be better off with tires that are considerably wider than stock, mounted on wider wheels.
Tread patterns have a major effect on traction. A smooth highway tread offers excellent adhesion on pavement, but loads up with mud or snow immediately and has almost no grip at all on these surfaces. "Mud and snow" or "all-terrain" treads have more open space between the cleats than highway tires and are a good compromise on a vehicle that is also a "daily driver" (although they are somewhat noisier than stock tires). "Mud grip" tires have very aggressive cleat patterns. They offer excellent traction in most off-highway conditions (except deep sand, where they may tend to dig in), but are noisy and degrade the vehicle's handling capabilities and grip on pavement.
Many drivers modify their vehicle's suspension for improved off-highway performance. While you see many trucks on the street that have been raised an extreme amount, you will never see these vehicles used by experienced drivers in difficult back country. Again, moderation is the key to success. The goals of suspension modifications are improved ground clearance and traction.
Another common modification is the addition of positive traction differentials, which deliver driving torque to both wheels on an axle if one wheel starts to spin. These come in a wide variety of configurations and prices, from factory-optional limited-slips (which are the cheapest way to go) to air-powered fully locking differentials that can be engaged by a dash-mounted button. These items drastically improve traction, to the point that a fully prepared vehicle can go over almost any road or trail that exists on the planet. They are relatively expensive, and installation is best left to professionals.
The ability to crawl along at a slow walking speed is probably the single most important ability of a good off-highway vehicle. To enhance this ability, many people install higher numerical final drive gears in their front and rear differentials. This also compensates for tires that are taller than stock. Again, this is not cheap and installation should be handled by a professional.
The most efficient form of automotive lighting available today is the quartz-halogen (QH) bulb. In general, an off-highway vehicle should have at least one "fog" or "cornering"-beam light and at least one "driving" or "euro"-beam light. So-called "pencil beams" are too narrow for our purposes. A large light with more reflector area will generally outperform a smaller light. There are dozens of manufacturers of QH auxiliary lights; in general, you get what you pay for. One each of these large lamps from a major manufacturer will provide a dramatic improvement in night vision.
Inexpensive QH "fog" lamps actually work quite well, though, and make excellent area lights for the rear or sides of the vehicle. A hand-held QH spotlight is a worthwhile accessory to have stored in the vehicle.
Auxiliary lighting and other electrical equipment commonly found on SAR off-highway vehicles, such as multiple radios and winches, can require a lot of power. As a general rule, an alternator should not be run at more than 75 percent of its rated output for extended periods, and winches place large demands on batteries. If you choose to equip your vehicle with this gear, you should consider an uprated alternator and a higher capacity battery. Some people install an extra battery just to power the winch. Be smart-carry jumper cables.
Anyone operating a vehicle off the highway should have a substantial amount of equipment with them at all times. This should be securely stowed in the vehicle, as loose objects can become lethal projectiles in an unexpected rollover or other sudden change in attitude. A good way to stow this equipment is in boxes bolted to the bodywork of the vehicle. These are commercially available, or can be custom made by the owner. Be sure to use good-sized washers between the bolt heads and the bodywork.
Store in these boxes: tools (including a hammer and tools sufficient to change accessory belts and tighten clamps and bolts), a comprehensive first-aid kit, jumper cables, a fire extinguisher, food, water, shelter, duct tape, baling wire, garbage bags and motor oil.
You should also carry spare parts: a full set of hoses, accessory belts, a fuel filter and a distributor cap. Make sure your spare tire is in good condition, and check its air pressure before each mission. Always have a spare ignition key, and take plenty of maps of the area you'll be searching.
Any vehicle operating off of paved roads is in danger of getting stuck. You should always have a sturdy jack, a good lug wrench and a jacking pad for loose or soft surfaces. A square piece of 3/4-inch plywood about one foot on a side makes an excellent jacking pad. An aftermarket "handyman"-type jack is a good investment, as is a "come-along" or electric winch. You should also carry a full-sized shovel and a good nylon tow strap. Traction aids such as tire chains or sections of chain-link fencing or expanded metal are useful in extreme conditions. The Boy Scout motto, "Be Prepared," is an excellent motto for everyone who ventures off-highway.
The most important piece of equipment the off-highway driver has is his brain! Off-highway travel is an exercise in control; done skillfully, it is highly mental. Keep an objective attitude. Know your vehicle's limitations, know your skill limitations and know the requirements of the mission. Observe, think, plan, then execute! Strive for elegance. The best off-pavement driver is one who is in control all the time, who thinks ahead and who never spins a wheel.
Whenever possible, don't travel alone. Always try to have at least two vehicles traveling together. The second vehicle should be careful not to follow the lead vehicle too closely. The lead vehicle may have to stop suddenly or back up.
In general, skillful off-highway driving requires planning, precision, concentration and smoothness. It has a lot in common with race driving; at the Indianapolis Motor Speedway, a driver must be extremely smooth and able to place his wheels within an inch of where he wants to or he will spin out or be too slow. In the back country, the driver must place his wheels exactly on top of that rock, or he will get stuck or damage the vehicle. Always think safety, smoothness and courtesy for other road users and the environment.
When you leave the pavement, it's a good idea to go into four-wheel drive right away. Rally racing has proven that four-wheel drive offers better control, even on dry, relatively smooth dirt roads-particularly under braking. The same improvement in control is noticeable at normal speeds, and if you engage four-wheel drive before you truly need it, you'll always be ready for the unexpected. One of the biggest advantages a four-wheel drive vehicle has over other vehicles is low range. Use it a lot-most of the time, slow is the best way to go in difficult terrain.
Know the legal vehicle restrictions in your search area. Know which roads and trails are closed to vehicles and respect those rules. Never travel off existing roads and trails unless it is a true emergency and off-road travel is allowed in the area.
When traveling up and down steep hills, never attempt to turn around on the middle of the hill. Always back straight down (or up) and try again. Turning around on a hill (or attempting to drive along the side of a steep incline) is the most common cause of an off-highway vehicle rollover. When traveling downhill, use the gearbox to control your speed. On really steep hills, use of the brakes while descending can cause the rear of the vehicle to slide, causing a loss of control and a possible rollover. Low range really helps in this situation. When climbing hills, use low range to steadily power your way up the hill without wheelspin. Conserve your momentum, and crest the hill slowly-the road may drop off or turn sharply. Be able to come to a full stop at the crest, if necessary.
If you encounter opposing traffic on a hill, the vehicle headed uphill has the right-of-way. When parking the vehicle in hilly terrain, always leave the vehicle in low range, first gear or reverse, set the parking brake and block the wheels-especially at high altitude. At high elevations, the air is thin enough that simple engine compression may not be enough to securely hold the vehicle in place.
Consider lowering the air pressure in your tires if you will be traveling in difficult terrain. Experienced drivers often air down to between one-half and two-thirds of highway pressures for rocky terrain, and down to ten PSI or less in sand. Before airing down, though, be sure that you have a way to increase the pressure to normal before driving on pavement. Operating tires that are severely underinflated on pavement can easily cause a failure and loss of control. Carry an air tank or some kind of air pump. There are many types of pumps available, from manual to electric compressors to pumps that screw into a spark plug location.
In rocky terrain, think like a technical climber. Plan each move, then execute it smoothly. Slow and steady is the way to travel this terrain elegantly. Use low range, first gear and drive like there's an egg between your foot and the pedal. Once you're rolling, try to control your vehicle with the gas pedal only; avoid using the clutch and brake, except to come to a full stop.
When you are faced with a particularly difficult section of road, get out and look it over. Is it really necessary to go this way? Is there an easier route? Can the section be improved by moving rocks? Once you have planned your route, proceed slowly in low range, with gentle changes in throttle setting. Always place your tires on top of large rocks, rather than trying to straddle them. Try to avoid or straddle ruts, but if you must cross ruts, do so at an angle.
If you have to cross a stream, always check out the footing first. Is it firm rock or gooey mud? Is it smooth or are there holes to avoid? Is the water deep or shallow? Does the water flow rapidly or slowly?
You must take all of these factors into account. Be sure that the stream is more shallow than the air intake of your engine; if you suck water into the engine, it will cause severe damage immediately. If you must cross the stream, cross at approximately right angles (or head slightly upstream) at a slow, steady rate. Don't create a "bow wave," and don't charge the stream, throwing up big sheets of water. That can harm the ecology of the stream and drown your ignition or cause major engine damage.
Low traction conditions-sand, mud or snow-require special techniques. Be even smoother than usual in everything you do. This is one situation where more speed, within reason, can help. Be sure to maintain momentum; low range is useful here. If you start to bog down, wiggle the steering back and forth a little bit to help the front tires bite. Do not spin your tires unless you are still making progress-you will quickly become very stuck! Stop and try to back out. If you know that you will have to drive in deep sand, mud or snow, try lowering the tire pressures a lot. If you typically encounter shallow mud or snow with a hard subsurface, narrower tires with higher pressures are effective.
If you do get stuck in deep sand, mud or snow, don't keep trying to blast your way out. You'll just dig in deeper. Jack up the vehicle and fill in the space under the tire with rocks, brush, boards, fencing, floor mats or anything else that you may have. This is where a top-quality jack, such as a "handyman-type" jack, is invaluable. These rugged jacks can lift more than three feet and are much stronger than a standard jack. Be sure to use a platform of some sort under the jack, or you may find that you are pushing the jack into the ground, rather than lifting the vehicle. Sometimes carefully jacking up the vehicle and pushing the vehicle off the jack to one side will work, particularly if you are high-centered. Use caution, though-this must be done very carefully to avoid damage or injury. Friction between the sidewalls and mud can really hold you in place, so dig out the mud from around the sidewalls. Make sure that you have a ramp to drive away on, rather than a ledge produced by wheelspin.
If you have another vehicle to help, use a tow strap. The best tow straps are heavy nylon, at least 25 to 30 feet long. Attach the strap to the tow hooks on your frame, if the vehicle has them. If not, attach the strap to a strong place, preferably the frame, that is not sharp. Do not use an ordinary hitch ball, and do not tie knots in the strap. The towing vehicle should slowly take out most of the slack, then accelerate briskly away. The nylon strap will work like a giant rubber band and, hopefully, slingshot the stuck vehicle out of its predicament. Be careful not to get the towing vehicle stuck, too!
Winches are extremely valuable devices for getting unstuck. They also can help move fallen trees from the road. A thorough discussion of winches can easily be the sole subject of a lengthy paper; see the bibliography for some good references. Winches are very useful, but they can be very dangerous when not used properly. Be sure to thoroughly read and understand the operational information that comes with your winch. Some general guidelines follow.
Always wear leather gloves when using a winch. If you need to attach the cable to a tree, use a tree strap to avoid damaging the tree's bark. If you are winching another vehicle to "unstick" it, put your vehicle in low range, first or reverse gear, set the parking brake and chock the wheels. Always pull as straight as possible, and stand in a safe place to avoid injury should the cable break. Most people raise their hood and stand behind a door when operating the winch. Always place a blanket or coat over the cable to act as an air brake if the cable snaps. A broken cable can be lethal.
If there is nothing to attach the cable to, you can use a "deadman" or cable anchor. This can be either a commercially available winch anchor or you can bury your spare tire. You can double the pulling power of the winch by using a "snatch block," which is a pulley designed for winching. When you are through winching, unwind the cable and respool it neatly onto the drum. Again, always wear leather gloves. Be sure not to drain your battery too much while winching-carry jumper cables just in case.
The proper equipping and operation of off-highway vehicles has been discussed. In general, it all comes down to thinking ahead, using common sense and being prepared. Strive for elegance-slow is usually the way to go. Practice your driving skills and you should avoid major problems in off-highway conditions, whether as part of a SAR mission or during recreational four-wheeling.