The requirement to have a CDL in order to drive a CMV (Commercial Motor Vehicle) has been mandatory since 1992, however a CDL by itself is not enough. Depending on the type of vehicle a driver operates, he or she may still be required to undergo testing for one or more CDL endorsements. Normally, the most common type of endorsement required is the one for air brakes. Air brakes are the most efficient and effective type of braking system for large, heavy vehicles but their use and maintenance requires special knowledge on the part of the commercial driver.

Air brakes normally consist of three different braking systems: the service brake, parking brake, and emergency brake. The service brake system operates when the brake pedal is used during normal driving. The parking brake system operates when the driver uses the parking brake control. The emergency brake system kicks in to stop a vehicle during brake system failure, and utilizes parts from both the service brake and the parking brake.

Knowing first what kind of air brake system a driver will operate should be top priority. If a driver is going to pursue an air brake endorsement, these are the things he/she should know first:

• Air Brake System Parts
• Dual Air Brake Systems
• Inspecting Air Brakes
• Using Air Brakes

Air Brake System Parts

Air brake systems are not standard on all vehicles; there are different types of systems depending on the make of the vehicle, and the date it was manufactured. There are many parts to an air brake system, and having an intimate knowledge of what each part does will make it easier for a driver to diagnose a potential problem. There are parts that are specifically designed to alert the driver if there's anything wrong, and knowing these parts is the key to maintaining proper air brake functionality in a vehicle.

Dual Air Brake Systems

Most of the bigger vehicles utilize a dual air brake system connected to one set of brake controls. These systems, designed for safety, control two separate sets of brakes for the front and rear axles. Maintaining proper air pressure in both the primary and secondary system is key to maintaining harmony in the dual system. Should the pressure in either system drop to 60 psi or lower, it will turn off that brake system and it will take longer for the vehicle to come to a complete stop. Should this happen, the safest option is parking the vehicle in the nearest available stop and getting the brake systems fixed.

Inspecting Air Brakes

There are more parts to inspect in a vehicle with air brakes than one without, and knowing how to properly inspect the parts for any possible trouble is key to maintaining safe vehicle operation. Since air brakes operate on compressed air, there will be several gauges and warning lights in the vehicle that would tell if air pressure is at optimum working efficiency. If there is any suspicion that the system is not working properly, the driver needs to take immediate action to prevent longer braking or the need to rely on the emergency brake due to failure of the system.

Using Air Brakes


Knowing how to use the braking systems properly is the first step in making sure that the air brake system(s) will last for a long time. Knowing how to perform emergency stops while the ABS (Antilock Braking System) is on, remembering to use the parking brake system, and knowing the proper stopping distance for the vehicle a driver would be operating are what makes for safe operation of vehicles with air brake systems.

In order to get proper training for air brake endorsement, a driver must pass a written exam, and perform specific maneuvers on the vehicle they plan to operate, in order to gauge their knowledge about air brake systems.

Learn more about how to get you CDL or take a FREE Air Brakes test at TestQuestionsAndAnswers.com.

Labels: air brakes, cdl, CDL endorsements, CDL practice test, commercial drivers license, commercial truck drivers, commercial vehicles

Big trucks, small trucks or medium trucks, regardless of their size, they are a natural part of the driving environment. They are driven by commercial drivers and play a substantial role in our commerce. It is important to learn about their characteristics and how to drive defensively around them.

So what should you keep in mind when sharing the road with trucks?

Take in account the differences in size and weight.

Due to their size and weight they can not react quickly in the driving environment. While most cars weigh an average of 3,000 pounds, large trucks are heavy and can weigh up to 80,000 pounds. At that weight trucks can't maneuver like a 3,000 pound car and can not be brought to a quick stop. In a crash involving a 3,000 pound car and an 80,000 pound truck, the truck is going to sustain less damage.

Increase your following distance.

When traveling behind a truck use extra caution and increase your following distance to three or fours seconds. Doing so allows you to have a better view of the traffic conditions ahead. If you are following at a safe distance, consider it will only cost you two or three seconds of your time to remain behind the truck as you approach your exit.

The most common mistake that drivers make around trucks is thinking trucks have the ability to perform and to stop like a small car. It takes at least twice the distance for a large truck or bus to stop than it does for a small car. It also takes them longer to accelerate and get up to speed.

Use extra care when passing.

The US Department of Transportation Office of Motor Carrier Safety conducted a study titled "The Unsafe Driving Acts of Motorists in the Vicinity of Large Trucks". The study found "Particularly distressing to truck drivers is when a motorist passes a large truck, quickly cuts in front of it, then exits the highway." They cited the most common reason for collisions involving passenger vehicles and large trucks was the motorists "unfamiliarity with the performance limitations and capabilities of large trucks. It appeared that most drivers are unaware of the limited acceleration, braking, and visibility of large trucks and of the relationship between mass and velocity and the potential consequences of that relationship to safety." They need lots of room to maneuver and have a much wider turning radius.

Be aware of the blind spots.

Avoid cruising along in a truck's blind spots. Large vehicles have very large blind spots or what is referred to as "No-Zones". Semis have a large blind spot reaching up to 200 feet directly behind them. As you near the cab on the left side there is a blind spot that runs from behind the cab to just behind the driver. There is a much larger blind spot on the right side of the vehicle. Trucks with high hoods have a blind spot of up to 25 feet in front of the truck. The old saying that "If you can't see the truck's mirrors, the truck driver can't see you" is true. Some go even further to say if you can't see the truck driver's face in his mirrors, he can't see you.

A study conducted by the AAA Foundation found that in collisions involving cars and trucks, the driver of the car was at fault 73 % of the time. Other studies have shown that:

Passenger-car drivers are four times more likely to rear-end a truck than truckers are to rear-end cars;

Non-commercial drivers are 10 times more likely to crash into a truck head-on than vice versa;

Passenger-car drivers are three times more likely to speed in poor road conditions (such as rain) than truck drivers;

Non-commercial drivers are eight times more likely to be involved in crashes involving drowsiness.

The AAA study also found that in fatal collisions involving cars and trucks, 98% of the deaths were among occupants of the car.

When sharing the road with trucks, give trucks a wide berth and respect their limitations.

For more information about truck safety or commerical drivers license (CDL) please visit www.TestQuestionsandAnswers.com.

Labels: cdl, commercial drivers license, driver safey, sharing the road with trucks, truck safety

Standards for testing and licensing Commercial Motor Vehicle (CMV) drivers are developed and issued by The Federal Highway Administration (FHWA). These standards mean that states can only issue Commercial Driver’s Licenses (CDLs) to CMV drivers if the drivers pass knowledge and skills tests that relate to the type of vehicle the driver will be operating. CMV drivers have been required to have CDLs since April 1, 1992.

Drivers may have a commercial drivers license (CDL) with certain endorsements or restrictions. Endorsements mean that a driver is qualified to operate a particular type of vehicle. Restrictions mean that a driver is not qualified to operate a particular type of vehicle. If a driver fails the air brake component of the general knowledge test or performs the skills test in a vehicle that does not have air brakes, the driver’s CDL will indicate that the driver is restricted from operating a CMV that has air brakes.

How Do Air Brakes Work?

Air brakes use compressed air to make the brakes stop the vehicle. There are actually three braking systems in the air brake system: service brake, parking brake, and emergency brake. The service brake system applies and releases the brakes when the brake pedal is used during normal driving. The parking brake system applies and releases the parking brakes when the parking brake control is used. The emergency brake system uses parts of the service and parking brake systems to stop the vehicle in a brake system failure.

Stopping distance is greater on vehicles with air brakes because with air brakes there is an added delay when stopping. The delay comes from the time required for the brakes to work after the brake pedal is pushed; it takes one-half second or more for the air to flow through the lines to the brakes. Drivers of CMVs with air brakes need to be aware of brake lag distance so they can allow for additional stopping distance.

What Do CDL Drivers Need to Know about Air Brakes?

All commercial motor vehicle operators must have knowledge of air brakes, unless they have a restriction on the CDL indicating that they are not qualified to operate a CMV with air brakes or have your CDL Air Brakes endorsement. The driver must have knowledge of:

• Air brake system nomenclature


• The risks of a contaminated air supply


• The consequences of severed or disconnected air lines between the power unit and the trailer(s)


• The implications of low air pressure readings


• A method of conducting a safe and accurate pre-trip inspection


• Procedures for performing en-route and post-trip inspections of air actuated brake systems, including the ability to identify defects which may cause the system to fail

Labels: air brakes, cdl, CDL endorsements, commercial drivers license

Drivers have been required to have a Commercial Driver's License (CDL) to drive a Commercial Motor Vehicle (CMV) since April 1, 1992. The Federal Highway Administration (FHWA) develops and issues standards for testing and licensing CMV drivers. Among other requirements, states are allowed to issue CDLs only after the driver passes knowledge and skills tests administered by the state that relate to the type of vehicle the driver wants to operate.

Drivers need CDLs if they are in interstate, intrastate, or foreign commerce and drive a vehicle that meets one of the definitions of a CMV. Drivers who operate special types of CMVs need to pass additional tests to obtain the necessary endorsement(s) on their CDL. Endorsement T is for drivers who operate CMVs with double or triple trailers (triple trailers are illegal in some states). Double and triple trucks are also known as Longer Combination Vehicles (LCVs). A knowledge test is required.

To obtain a double/triple trailers endorsement, applicants must have knowledge of:

Procedures for assembly and hookup of the units

Proper placement of the heaviest trailer

Handling and stability characteristics including off tracking, response to steering, sensory feedback, braking, oscillatory sway, rollover in steady turns, and yaw stability in steady turns

Potential problems in traffic operations, including problems the motor vehicle creates for other motorists due to slower speeds on steep grades, longer passing times, possibility of blocking entry of other motor vehicles on freeways, splash and spray impacts, aerodynamic buffeting, view blockages, and lateral placement.

The U.S. Department of Transportation (DOT) Federal Motor Carrier Safety Administration (FMCSA) has developed minimum training requirements for operators of LCVs. There are also special requirements for classroom and skills instructors who train LCV drivers. For purposes of this training, an LCV is defined as any combination of a truck-tractor and two or more trailers or semi-trailers that has a gross vehicle weight rating greater than 80,000 pounds and operates in interstate commerce. Twin trailers, also known as western doubles, are not subject to this rule, because they have a gross vehicle weight rating of 80,000 pounds or less. These rules were effective June 1, 2004.

LCV training consists of both driving and non-driving activities. Non-driving activities include activities such as route planning and checking cargo and weight. There are different training courses for LCV doubles and triples because they have different operating characteristics.

To qualify for doubles training, drivers must show six months of driving experience in vehicles with a Gross Combination Weight Rating (GCWR) of 26,001 or more pounds. For the triples training, drivers must show six months of truck-tractor/semitrailer or twin-trailer experience.

Labels: cdl, commercial drivers license, endorsements, triple trailers

View Full Post posted by NSC - Traffic Safety : 9:16 AM