Ch 15-17

Question 1

greatest concern for w/ tractor-trailer operations

Answer 1

jackknife
- when some of the tires lose traction

Question 2

the different jackknife circumstances

Answer 2

1. front tires of tractor lock: lose steering control, will usually skid in straight line
2. rear tires of tractor lock: rear of tractor will want to spin around, causing jackknife
3. rear tires of tractor lose traction due to sudden acceleration: drive axle will lose traction causing spinout and jackknife
4. Rear tires of tractor lose traction b/c engine brake is on in wet weather
5. trailer tires lock: trailer at risk of swinging out, usually slower than tractor so driver has time to correct it

Question 3

Causes/Preventing jackknifes

Answer 3

1. over acceleration
2. failure to turn of engine brake on wet roads
3. aggressive braking: drive appropriate speed, smooth braking, anticipate hazards
4. driving on 2 dif. surfaces

Question 4

Tiller lader skid control

Answer 4

• 1st step is to let off offending pedal
• if its the tractor skidding, let off offending pedal, look where you want the vehicle to go, steer in that direction
• when trailer is swinging out, tiller operator may be able to steer back in line, but don’t rely on them to regain control

Question 5

trailer rollovers

Answer 5

• drive will not sense warning signals of the trailer braking traction or starting to roll
• 1st warning will be by watching the trailer or worse, starting to feel the tractor roll as the rolling trailer pulls it
• tiller operator must stay in constant contact w/ driver, advising if driving too fast
• driver must keep tiller operator aware of planned route and upcoming turns
• Communication is key
• helpful to maintain teams on a regular basis

Question 6

backing operations

Answer 6

• tiller operator is a set of eyes in the rear
• must be aware of blindspots associated w/ sitting high on top of vehicle
• backup camera still recommended

Question 7

turning a tiller ladder

Answer 7

• excessive speed may force the tiller operator to oversteer or lose control because they won’t have enough time to correct steering angle and bring back in line
• after the turn, driver must ensure tiller op has brought trailer back in line and wheel straightened
• tiller op must remember to disengage the 5th wheel lockout (provides stability for aerial device) prior to leaving scene. It may put a bend in the truck, causing poor handling as all tires won’t be in full contact w/ the road
• w/ appropriate speed and proper positioning, tiller op will have to make minimal steering corrections and should only be done when there’s a need
• ensure enough space for overhang

Question 8

overhang

Answer 8

• portion of the vehicle from rear axle to rear of the truck
• tiller operator must ensure enough space for the trucks overhang

Question 9

Statistics on 15-passenger vans

Answer 9

• b/t 1990-2002: 1,576 fatal van crashes, 1,111 fatalities were occupants, 86% of those were not wearing seatbelts, 92% wearing seatbelts survived
• rollover 2.2x more likely if loaded to more than half capacity
• 5x when fully loaded compared to only driver
• 5x when on high speed road (greater than 50mph)
• 2x on a curved road

Question 10

Rollovers in 15-passenger vans

Answer 10

• more occupants = center of gravity higher and toward rear
• most common 3 scenarios:
  1. goes off a rural road
  2. driver fatigue
  3. overcorrection as a panic reaction to a roadway emergency or wheel dropping off pavement

Question 11

implementing safety procedures for 15-passenger vans

Answer 11

• age requirements: there are age requirements for large apparatus but not smaller vehicles. Should be over 21 y/o
• number of passengers: 9 max, in front of rear axle
• speed
• seatbelts
• fatigue: switch every 2 hours and avoid overnight travel
• distractions
• tire pressure: 74% of the fatal accidents did not have properly inflated tires

Question 12

selecting a tow vehicle/damage resulting from an oversized load

Answer 12

• knowing how much weight the tow vehicle can pull is the first step in trailer safety
• tow packages typically include heavy-duty engine w/ trans cooler, oversized mirrors, heavy-duty rear suspension, and wiring for the trailer
• damage resulting from an oversized load
  1. brake components
  2. transmissions: excess heat breaks down trans fluid, lack of lubrication, causes breakdown of trans mechanical components or total failure if it seizes
  3. suspension components

Question 13

selecting a hitch
(terminology)

Answer 13

• tongue: v-shaped portion of trailer including the coupler
• tongue weight: transferred to tow vehicle at hitch point, should be 9%-15% of total trailer weight. Too light will cause sway,
• gross trailer weight: total trailer weight
• gross combined vehicle weight rating: total weight of vehicle, trailer, passengers and equipment
• gross vehicle weight rating
• Hitch ball: coupler latches to it. Ensure proper size for coupler, 3 sizes:
  1. 1 7/8” - up to 2k lbs
  2. 2” - 3,500-8,000lb(most common
  3. 2 5/16” - 6,000-30,000 lbs
• Draw bar: ball mount, 2 sizes (1 1/4”, 2” square)
• coupler: drops over hitch ball, 4 types:
  1. weight carrying hitch: carries all tongue weight on ball and receiver
  2. weight distributing hitch: across tow vehicles entire frame w/ “spring bars”
  3. 5th wheel hitch: mounted on bed of truck forward of rear axle
  4. gooseneck hitch: similar to 5th wheel, uses ball hitch instead of locking pin

Question 14

Electromagnetic trailer brakes

Answer 14

• electrical current is sent through an electromagnet found inside brake drum
• brake controller determines how much electricity/force is applied
• advantages
  1. ability to engage separately from vehicle
  2. alleviate trailer sway
  3. helpful when descending hills
• disadvantages
  1. problems when used infrequently, rust
  2. requires brake controller installation
• can be applied manually and/or brake pedal
• 2 types of brake controllers:
  1. time delay: preset amount of force
  2. proportional: applies at same intensity as brake pedal

Question 15

surge braking systems on trailers

Answer 15

• activated by momentum of decelerating trailer
• trailer pushes against hitch and engages hydraulic master cylinder, engaging brake system on trailer

Question 16

trailer breakaway systems

Answer 16

• cord or cable b/t trailer and truck that will automatically engage trailer brakes

Question 17

1st step in safe trailer operations…

Answer 17

properly secure the trailer to the tow vehicle

Question 18

Ensure that chains are used at all times and that the chains are _____.

Answer 18

• crossed
• creates a “nest” for the tongue of the trailer instead of slamming on the ground

Question 19

Trailers: acceleration considerations

Answer 19

• allow more time and space when entering road or making turns
• excess speed can cause trailer sway, longer stopping dist., issues w/ curves and lane changes

Question 20

Trailers: braking considerations

Answer 20

• braking efficiency
• incr stopping distance
• more susceptible to skids/jackknifes
• downshift using retarding force of engine to slow vehicle, reducing brake fade

Question 21

Trailers: turning and curves

Answer 21

• trailer wheels can “off-track”, travel in a different line than vehicle
• if taller than vehicle, may have lower rollover threshold

Question 22

Trailers: backing

Answer 22

• place hands on bottom of steering wheel, direction of hand mvmnt is where the trailer will go
• shorter the dist. b/t axles, the more difficult it will be
• use at least one spotter

Question 23

trailer sway

Answer 23

• excess side-to-side mvmnt of trailer
• more common in trucks w/ soft suspension and longer dist. b/t rear axle and hitch
• causes:
  1. weight distribution
  2. wind
  3. tractor trailers: bow wind
  4. roads: uneven, bumpy, 2 dif. surfaces

Question 24

NFPA chapter dealing specifically with trailers

Answer 24

NFPA 1901-Ch 26