CDL combination vehicles practice test

C: Heavier and longer, and they need more driving skill. Combination vehicles are usually heavier and longer and need more driving skill than single commercial vehicles, so their drivers need more knowledge and skill. Commercial Driver's License Manual (CDL Driver's Manual): 6.1 Driving Combination Vehicles Safely, page 6-1.

B: More than half. Rollovers account for more than half of the truck drivers killed in crashes, which is why the manual stresses keeping loads low and taking turns slowly. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.1 Rollover Risks, page 6-1.

D: It can turn the trailer over. Trucks with trailers have a dangerous crack-the-whip effect. A quick lane change can turn the trailer over, and in many crashes only the trailer has overturned. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.2 Steer Gently, page 6-1.

A: At least 1 second for each 10 feet of vehicle length, plus another second. Keep at least 1 second for each 10 feet of vehicle length, plus another second if you are going over 40 mph. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.2 Steer Gently, page 6-1.

A: When empty. An empty combination rig needs more distance to stop than a fully loaded one. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.3 Brake Early, page 6-1.

C: Get out of the vehicle and away from the tracks. If you get stuck on the tracks for any reason, get out of the vehicle and away from the tracks. Then call for help. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.4 Railroad-highway Crossings, page 6-2.

B: The rear wheels following a different path than the front wheels when going around a corner. Off-tracking (or 'cheating') is when the rear wheels take a tighter path through a turn than the front wheels. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.6 Turn Wide, page 6-3.

D: All the air might leak out, unlocking the brakes on trailers without spring brakes. Never park with the hand valve: all the air might leak out and unlock the brakes on trailers that don't have spring brakes. Use the parking brakes, and chock trailers without spring brakes. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.1 Trailer Hand Valve, page 6-4.

B: Look far enough down the road. Scanning well down the road lets you spot trouble early, so you aren't forced into an abrupt lane change. Also slow to a safe speed before turning. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.2 Steer Gently, page 6-1.

C: It moves higher up from the road, making the truck easier to turn over. Piling up more cargo raises the center of gravity, and the truck becomes easier to turn over. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.1 Rollover Risks, page 6-1.

D: Rearward amplification. Rearward amplification causes the crack-the-whip effect during quick lane changes. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.2 Steer Gently, page 6-1.

B: 7 seconds. One second for each 10 feet gives 6 seconds for a 60-foot rig, plus one more second over 40 mph, for 7 seconds. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.2 Steer Gently, page 6-1.

D: The very stiff suspension springs and strong brakes give poor traction. With a light load, the stiff springs and powerful brakes don't give the tires much grip, so the wheels lock up very easily. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.3 Brake Early, page 6-1.

D: The crossing's location using identifiable landmarks, especially the DOT number if posted. Check signposts or the signal housing for emergency notification information, call 911 or another emergency number, and give the crossing's location using all identifiable landmarks, especially the posted DOT number. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.4 Railroad-highway Crossings, page 6-2.

D: The rear wheels of the last trailer. The tractor's rear wheels off-track some and the trailer's rear wheels more. With more than one trailer, the rear wheels of the last trailer off-track the most. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.6 Turn Wide, page 6-3.

C: Its emergency brakes hold only while there is air in the trailer tank; when the air leaks away, there are no brakes. Trailers without spring brakes have emergency brakes that work from stored tank air and no parking brake. The air will eventually leak away and leave no brakes, so chock the wheels. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.8 Trailer Service, Parking and Emergency Brakes, page 6-6.

A: In the opposite direction from the way you want the trailer to go. Backing a trailer is the reverse of backing a car, straight truck or bus: steer the top of the wheel away from the direction you want the trailer to go. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.7 Backing with a Trailer, page 6-3.

A: Ten times as likely. A rig with a full load is ten times as likely to roll over in a crash as an empty one, because the cargo raises the center of gravity. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.1 Rollover Risks, page 6-1.

C: The rear trailer is twice as likely to turn over as the tractor. On the rearward amplification chart, 2.0 means the rear trailer is twice as likely as the tractor to tip over. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.2 Steer Gently, page 6-1.

B: So you can brake early and avoid a panic stop. Allowing lots of following distance and looking far ahead lets you brake early so you aren't caught by surprise and forced into a panic stop. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.3 Brake Early, page 6-1.

C: A tractor without a semitrailer; it can be very hard to stop smoothly and takes longer to stop than a fully loaded tractor-semitrailer. A bobtail is a tractor running without a semitrailer. Tests show it is very hard to stop smoothly and needs more distance to stop than a tractor-semitrailer at maximum gross weight. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.3 Brake Early, page 6-1.

B: The trailer tends to swing around (a trailer jackknife). When trailer wheels lock up, the trailer tends to swing around. This type of jackknife is often called a trailer jackknife. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.5 Prevent Trailer Skids, page 6-2.

B: Longer vehicles off-track more. Longer vehicles will off-track more. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.6 Turn Wide, page 6-3.

D: If the trailer doesn't have spring brakes, or if you're not sure. Chock the trailer if it lacks spring brakes or you aren't sure. If its tank air leaks away, the emergency brakes release and the trailer could roll. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.2 Uncoupling Tractor-Semitrailers, page 6-9.

A: Turn the wheel the other way to follow the trailer. Once the trailer starts to turn, turn the wheel the other way to follow it. Commercial Driver's License Manual (CDL Driver's Manual): 6.1.7 Backing with a Trailer, page 6-3.