Allow one second for every 10 feet of vehicle length, which gives 4 seconds for 40 feet, and add one more second because you are going faster than 40 mph.
More room ahead lets you slow down gradually if traffic stops, which gives the tailgater time to react and makes a rear-end crash less likely. Avoid tricks like flashing your brake lights, and do not wave other drivers past.
The compressor is linked to the engine through gears or a V-belt, and the engine's power lets it pump air into the storage tanks. Some compressors are cooled by the engine's cooling system, but the radiator does not drive the compressor, and neither does the drive shaft.
Backing toward the driver's side lets you look straight out your window and watch the back of the vehicle as it moves. Backing toward the right leaves much of the area hidden and is far more dangerous, and a helper is still a good idea either way.
Rising BAC weakens judgment and self-control, which is why many drinkers believe they are fine to drive when they are not. Nothing makes the body clear alcohol faster; the liver breaks it down at its own steady pace.
A combination vehicle tips over most easily when its center of gravity is high and it takes a turn too fast. Loading cargo as low as possible and slowing down for turns address both causes, so they are the two most important precautions.
Stops along the route are the time to confirm that the load and its tie-downs are still holding and that tires and brakes are not running hot. Neither check can be skipped because it was done before departure or will be done at the destination.
Lock rings that are mismatched, bent or cracked are dangerous, as are clamps, spacers, studs or lugs that are missing. Also watch for damaged rims, any wheel or rim that has been repaired by welding, and rust around the lug nuts, which may mean they are loose.
At 55 mph on a dry road, the distance covered while you notice the hazard, react and brake adds up to roughly 400 feet, about the length of a football field. Large vehicles need far more room to stop than most drivers expect, so leave plenty of space ahead.
The sharper the turn, the higher the risk of skidding or rolling over, so steer only as much as needed to clear the hazard and be prepared to countersteer. Grip the wheel firmly with both hands, and avoid braking while turning, because braking may lock the wheels and cause a skid.
A heavy truck's brakes, tires, springs and shock absorbers are designed to work best under a full load. Without that weight the truck has less traction, so it needs a longer distance to come to a stop.
Below 40 mph you need one second for each 10 feet of length, so a 100-foot rig needs 10 seconds. Above 40 mph you add one more second, for a total of 11.
A healthy engine builds normal oil pressure almost immediately, within seconds of starting. If the gauge stays low, shut the engine off at once, because running it without proper lubrication can quickly cause serious damage.
That emblem identifies a slow-moving vehicle, such as farm or construction equipment, which typically travels at 25 mph or less. Reduce speed early and pass only when it is safe; the emblem has nothing to do with hazmat loads or police.
Drivers need time to react, so if a hill or curve means they cannot see your stopped vehicle from 500 feet away, the rearmost triangle has to go farther back along the road. Triangles must be set out within 10 minutes of stopping, however long you plan to stay, and taillights alone are not a dependable warning.
Tip When a hill or curve limits the view, the rear triangle may need to go anywhere from 100 to 500 feet behind your vehicle.
A vehicle that has to stop at a railroad crossing, including one hauling hazardous materials, should halt no closer than 15 feet and no farther than 50 feet from the nearest rail. From there, look and listen in both directions before going across.
High beams light the road much farther ahead, so use them whenever it is safe and legal. Dim them when traffic is coming toward you or when you are close behind another vehicle.
Wet pavement gives your tires less grip and makes stopping take longer, so slow down by roughly a third; for instance, go from 60 mph down to about 40 mph. Packed snow calls for an even bigger cut, about half or more.
After a tire fails, braking can make you lose control. Grip the wheel firmly and let the vehicle lose speed on its own before braking gently and pulling off the road; brake sooner only if a collision is about to happen.
A failed ABS still leaves the regular brakes working, so there is no reason to stop the bus or panic; simply brake as you normally would. Have the system fixed soon, though, instead of waiting for routine maintenance.
A burning tire has to be cooled, and that often takes a lot of water. Opening the hood or the cargo doors lets in fresh air that makes the fire burn faster, so keep them shut whenever possible.
Putting chains on during a storm without any prior practice is slow and dangerous, so learn the steps in good conditions first. Chains also need regular checks for broken hooks, worn cross-links and bent or broken side chains.
Air brakes combine a service brake for normal stops, a parking brake to hold the vehicle in place, and an emergency brake that uses parts of both of those systems to stop the vehicle if the brakes fail. A drum brake is a type of brake hardware and an engine brake is a separate retarder, so neither is one of the three systems.
An escape ramp is designed to bring a vehicle that can no longer slow down on a long downgrade, usually because its brakes have failed, to a safe stop. Any vehicle in that situation may use one; it is not limited to tank vehicles or combination vehicles.
Locked wheels make the vehicle slide, and sliding tires cannot steer it, so brake hard but ease up whenever the wheels lock, then reapply. Turning off the front brakes is never a safe way to stay straight.
Drivers judge shift points either by engine speed, watching the tachometer for the right rpm, or by road speed, knowing which mph range each gear covers. Traffic, following distance and weather affect how you drive, but they do not tell you when to shift.
Safety comes first: a careful inspection catches defects before they can cause a breakdown or a crash, protecting you and everyone who shares the road with you.
The warning means air pressure has fallen below a safe level, and if it keeps dropping, the spring brakes can come on by themselves, usually somewhere between 20 and 45 psi. Stop in a safe spot while you still have control rather than waiting for the brakes to lock on in traffic.
The standee line is the boundary that keeps standing riders out of the driver's area; no one may stand forward of the rear edge of the driver's seat.
Many carriers have rules on matters such as smoking, drinking or playing music, and announcing them as the trip begins heads off disputes before they start.
Operating a vehicle that must display hazardous materials placards is illegal unless your CDL carries the hazmat endorsement, and that holds for any distance, even a short hand-off. Pulling the placards off would only add another violation, because the shipment still legally requires them.
Air brakes need about half a second of brake lag before they take hold, which adds roughly 32 feet at 55 mph to the perception, reaction and braking distances. Altogether, the stop takes more than 450 feet even on dry pavement with good brakes.
This snub-braking method keeps the brakes from overheating and fading: with the engine doing most of the work in a low gear, brake firmly enough to feel a clear slowdown, let off once you are roughly 5 mph under your safe speed, and brake again when you are back up to the safe speed. Constant or ever-increasing pressure heats the brakes until they fade.
Because the cargo sits high, a tanker is top-heavy and can tip over more easily, and liquid in a tank that is not full can slosh and shove the vehicle. Cargo value, schedules, trailer width, and cab visibility are not why tankers need extra care.
At their stop, students must be told to move 10 feet or more away from the bus's side, which lets the driver see and count every one of them before pulling out. A step or two from the door still leaves a child in an area the driver may not be able to see.
Beer (12 ounces), wine (5 ounces) and liquor (1.5 ounces) all hold roughly equal amounts of alcohol per serving, so several of any one impair a driver just the same. Only the passage of time brings BAC down; showers and coffee do not, and people who drink often are impaired as well.
Construction areas bring narrowed lanes, workers, and sudden slowdowns, so a large vehicle should go through slowly and carefully. Flashing your brake lights or using hazard flashers also warns the drivers behind you that you are slowing, so each listed action is recommended.
By common convention the red line is the emergency (supply) line and the blue one is the service (control) line. Mixing them up when coupling can keep the trailer brakes from working properly, so check each connection.
With stab braking you push the brakes all the way down, let up as soon as the wheels lock, and press fully again once they start rolling; it is meant for vehicles without antilock brakes. Steady pressure that stops short of lockup is a different method called controlled braking.
Cargo that rides high raises the center of gravity, which makes the vehicle easier to roll over in curves and on ramps even when its weight is within the legal limit. Keep the heaviest freight low and spread the weight evenly.
Placards are required on each end and each side of the vehicle, four in all, so that anyone approaching it, especially police and firefighters, can see the warning whichever way they come from.
Any hazardous materials in a load must be described on its shipping papers, such as the bill of lading, where those entries are set apart so they are easy to spot. Opening containers is not how cargo is identified and could expose you to the very danger you are trying to find.
A pressurized cooling system holds steam and scalding coolant that can spray out and cause severe burns, so leave the cap alone until everything has cooled. If the engine overheats, stop as soon as it is safe instead of pushing on, and keep coolant at the proper level in every season.
A signal that has stayed green for a while may switch to yellow at any moment, so lift off the accelerator and be prepared to stop instead of racing to get through. A large vehicle also needs extra distance to stop.
A trailer skid usually begins when the trailer wheels lock, so letting off the brakes allows them to roll, grip the road again and fall back in line behind the tractor. Pulling the trailer hand brake will not straighten the rig; it only makes the slide worse.
Spraying the base hits the fuel that is actually burning instead of wasting the extinguisher on the flames above it. Stay as far back as you can while still reaching the fire, and keep the wind at your back so smoke and heat move away from you.
The basic guideline is one tie-down for every 10 feet of cargo length, and any load that can shift needs at least two, however short it is. Spacing them farther apart leaves parts of the load free to move.
Taking your foot off the gas lets the vehicle lose speed gradually until the tires cut through the water and grip the pavement again. Adding power, braking hard, or making sharp steering moves can send the vehicle into a skid.
Because the suspension squats under weight, a truck rides lower when loaded and higher when empty, so an overpass you cleared with a load may be too low on the trip back. Posted heights can also be wrong after repaving or packed snow, so never assume they are accurate.
Changing lanes safely calls for several mirror checks: before you signal, to see if there is space; after you signal, to make sure no one has entered your blind spot; just after you begin the move, to confirm the way is still open; and when the lane change is finished.
Every question in this set has its own page with the correct answer and an explanation.
