Double

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This endorsement is required if the driver will pull two or three trailers. To receive this endorsement, applicants must pass a..

This endorsement is required if the driver will pull two or three trailers. To receive this endorsement, applicants must pass a test. The test consists of 20 multiple choice questions. To pass, the applicant must answer at least 16 questions correctly. Each question has four possible answer choices. Test questions come from the Indiana Commercial Driver License Manual. Questions come from chapters covering: Driving Safely, Air Brakes (if applicable), Combination Vehicles and Doubles and Triples. The Double/Triple endorsement can be used with the Class A CDL.

Passing grade:

How does doubling your speed from 20 mph to 40 mph affect your vehicle's braking distance?

Explanation
Increasing your vehicle's speed will increase your vehicle's striking power and braking distance. Doubling your vehicle's speed from 20 to 40 mph will multiply its braking distance by four.

Rollovers happen when:

Explanation
Rollovers happen when a vehicle is driven too fast. To reduce the risk of rollover, make sure the weight of cargo is loaded low to the ground, and that you take turns and curves slowly.

What is the minimum permitted size of a placard?

Explanation
Hazardous materials must be diamond-shaped and a size of at least 10 ¾ square inches.

Air tank drains:

Explanation
In an air brake system, the air storage tanks must be drained to remove accumulated water and compressor oil. Failing to do so can cause damage. Manually operated drains should be used at the end of each day of driving.

When other vehicles have trouble seeing you at dawn or dusk, you can increase your visibility by:

Explanation
At dawn or dusk, and in snowy or rainy conditions, you should turn on your headlights to make it easier for other road users to see your vehicle.

To confirm that a trailer has ABS, you can:

Explanation
If you are unsure if a trailer is equipped with an Anti-Lock Braking System (ABS), look under the vehicle for the electronic control unit and wheel speed sensor wires coming from the back of the brakes.

When using road speed to know when to switch gears, you should:

Explanation
There are two indicators that determine when you need to shift into a higher gear. One indicator is the engine speed (rpm). You should read your vehicle's manual to learn its rpm range and shift up when you reach the top of that range. The other indicator is road speed (mph). You should learn which speeds each gear can accommodate, then keep an eye on the speedometer and shift up as needed.
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