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2.6 Controlling Speed (continued)

Slippery Surfaces

It will take longer to stop and be harder to turn without skidding when the road is slippery. You must drive slower to be able to stop in the same distance as on a dry road. Wet roads can double stopping distance. Reduce speed by about one-third (e.g., slow from 55 to 35 mph) on a wet road. On packed snow, reduce speed by half or more. If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so.

Identifying slippery surfaces:

Sometimes it is hard to know if the road is slippery. Following are signs of slippery roads:

  • Shaded areas - Shady parts of the road will remain icy and slippery long after open areas have melted.
  • Bridges - When the temperature drops, bridges will freeze before the road will. Be especially careful when the temperature is close to 32 degrees F.
  • Melting ice - Slight melting will make ice wet. Wet ice is much more slippery than ice that is not wet.
  • Black ice - Black ice is a thin layer that is clear enough that you can see the road underneath it. It makes the road look wet. Any time the temperature is below freezing and the road looks wet, watch out for black ice.
  • Vehicle icing - An easy way to check for ice is to open the window and feel the front of the mirror, mirror support or antenna. If there is ice on them, the road surface is probably starting to ice up.
  • Just after rain begins - Right after it starts to rain, the water mixes with oil left on the road by vehicles. This makes the road very slippery. If the rain continues, it will wash the oil away.

Hydroplaning

In some weather, water or slush collects on the road. When this happens, your vehicle can hydroplane. It is like water skiing: the tires lose contact with the road and have little or no traction. You may not be able to steer or brake. You can regain control by releasing the accelerator and pushing in the clutch. This will slow your vehicle and let the wheels turn freely. If the vehicle is hydroplaning, do not use the brakes to slow down. If the drive wheels start to skid, push in the clutch to let them turn freely.

It does not take a lot of water to cause hydroplaning. Hydroplaning can occur at speeds as low as 30 mph if there is a lot of water. Hydroplaning is more likely if tire pressure is low or the tread is worn. (The grooves in a tire carry away the water; if they are not deep, they do not work well.) Be especially careful driving through puddles. The water is often deep enough to cause hydroplaning.

Speed and Curves

Drivers must adjust their speed for curves in the road. If you take a curve too fast, two things can happen. The wheels can lose their traction and continue straight ahead, so you skid off the road, or the wheels keep their traction and the vehicle rolls over. Tests have shown that trucks with a high center of gravity can roll over at the posted speed limit for a curve.

Slow to a safe speed before you enter a curve. Braking in a curve is dangerous because it is easier to lock the wheels and cause a skid. Slow down as needed. Do not exceed the posted speed limit for the curve. Be in a gear that will let you accelerate slightly in the curve. This will help you keep control.

Speed and Distance Ahead

You should always be able to stop within the distance you can see ahead. Fog, rain or other conditions may require that you slow down to be able to stop in the distance you can see. At night, you cannot see as far with low-beams as you can with high-beams. When you must use low-beams, slow down.

Speed and Traffic Flow

When you are driving in heavy traffic, the safest speed is that of other vehicles. Vehicles going the same direction at the same speed are not likely to run into one another. Drive at the speed of other traffic, if you can without going at an illegal or unsafe speed. Keep a safe following distance.

Speed on Downgrades

Your vehicleʼs speed will increase on downgrades because of gravity. Your most important objective is to select and maintain a speed that is not fast for the:

  • Total weight of the vehicle and cargo.
  • Length of the grade.
  • Steepness of the grade.
  • Road conditions.
  • Weather.

If a speed limit is posted, or there is a sign indicating “Maximum Safe Speed,” never exceed the speed shown. Also, look for and heed warning signs indicating the length and steepness of the grade. You must use the braking effect of the engine as the principal way of controlling your speed on downgrades. The braking effect of the engine is greatest when it is near the governed RPMs and the transmission is in the lower gears. Save your brakes so you will be able to slow or stop as required by road and traffic conditions. Shift your transmission to a low gear before starting down the grade and use the proper braking techniques. Please read carefully the section on going down long steep downgrades safely in Mountain Driving.

Be very familiar with this paragraph, especially the following:

  • Wet roads can double stopping distance.
  • Reduce speed by about one-third on a wet road.
  • On packed snow, reduce speed by half or more.
  • If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so.
Be preaprared to explain what you should do if you hydroplane. Remember that you should not use the brakes and if you have a manual transmission, put the clutch in to allow the wheels to turn freely until you regain traction.
We've seen this statement a couple times now and it shows up on the written exam quite a bit. Slow down before a curve, not during a curve!
You should take special note and familiarize yourself with the below list.
Once again, we've seen this statement a couple times already. Slow down and select a proper gear before starting down a grade, not during the grade! Also make note that you should primarily use engine braking on a decline whenever possible in order to more effectively use your brakes when needed.

OWI:

Operating While Intoxicated

Review Questions - Click On The Picture To Begin...

Which is the best way to check for icing conditions (choose the best answer)?
  • Stop on the shoulder of the road so you can get out and manually check the roadway surface for ice
  • Turn on a weather radio for temperature reports
  • Ask other drivers over the CB radio if icing is present
  • Open the window and feel the front of the mirror, mirror support or antenna. If there is ice on them, the road surface is probably starting to ice up

Quote From The CDL Manual:

An easy way to check for ice is to open the window and feel the front of the mirror, mirror support or antenna. If there is ice on them, the road surface is probably starting to ice up.

Next
The following factors should be considered when determining your proper downgrade speed except:
  • Length and steepness of the grade
  • Total weight of the vehicle and cargo
  • Speed of vehicles around you
  • Weather and road conditions

Quote From The CDL Manual:

Speed on Downgrades - Your vehicle's speed will increase on downgrades because of gravity. Your most important objective is to select and maintain a speed that is not fast for the:

  • Total weight of the vehicle and cargo.
  • Length of the grade.
  • Steepness of the grade.
  • Road conditions.
  • Weather.

If a speed limit is posted, or there is a sign indicating "Maximum Safe Speed," never exceed the speed shown. Also, look for and heed warning signs indicating the length and steepness of the grade. You must use the braking effect of the engine as the principal way of controlling your speed on downgrades. The braking effect of the engine is greatest when it is near the governed RPMs and the transmission is in the lower gears. Save your brakes so you will be able to slow or stop as required by road and traffic conditions. Shift your transmission to a low gear before starting down the grade and use the proper braking techniques.

Prev
Next
When should high-beam headlights be used?
  • Anytime it's safe and you're legally allowed to do so
  • During the daytime to help others see you
  • When driving through heavily traveled city streets
  • All of these are good times to use high-beam headlights

Quote From The CDL Manual:

Use high-beams: Some drivers make the mistake of always using low-beams. This seriously cuts down on their ability to see ahead. Use high-beams when it is safe and legal to do so. Use them when you are not within 500 feet of an approaching vehicle.
Prev
Next
What is Black Ice?
  • Very cold liquid water on the roadway surface that has not yet frozen
  • A thin layer of ice that is clear enough that you can see the road underneath it
  • Ice which forms in conditions that are above freezing
  • A highly visible sheet of ice often formed over black surfaces

Quote From The CDL Manual:

Black ice is a thin layer that is clear enough that you can see the road underneath it. It makes the road look wet. Any time the temperature is below freezing and the road looks wet, watch out for black ice.

TruckingTruth's Advice:

Black ice is called "black" because it often forms over black asphalt surfaces. However, black ice is completely transparent and can form over any colored surface including brick, concrete, and cement. Black ice will appear to be the color of whatever surface it forms over and normally makes the surface appear to be wet.

Prev
Next
What is hydroplaning?
  • A loss of steering or braking control when a layer of water prevents direct contact between tires and the road surface
  • Loss of traction due to excessive icing on the roadway
  • Loss of traction due to loose sand or gravel on the roadway
  • Increased stopping distance due to friction created by standing water

Quote From The CDL Manual:

In some weather, water or slush collects on the road. When this happens, your vehicle can hydroplane. It is like water skiing: the tires lose contact with the road and have little or no traction. You may not be able to steer or brake. You can regain control by releasing the accelerator and pushing in the clutch. This will slow your vehicle and let the wheels turn freely. If the vehicle is hydroplaning, do not use the brakes to slow down. If the drive wheels start to skid, push in the clutch to let them turn freely.

It does not take a lot of water to cause hydroplaning. Hydroplaning can occur at speeds as low as 30 mph if there is a lot of water. Hydroplaning is more likely if tire pressure is low or the tread is worn. (The grooves in a tire carry away the water; if they are not deep, they do not work well.) Be especially careful driving through puddles. The water is often deep enough to cause hydroplaning.

Prev
Next
How will wet roads affect your stopping distance?
  • Wet roads have little effect on stopping distance
  • Wet roads can decrease stopping distance by washing away oil and other foreign liquids from the roadway surface
  • Wet roads can triple stopping distance
  • Wet roads can double stopping distance

Quote From The CDL Manual:

It will take longer to stop and be harder to turn without skidding when the road is slippery. You must drive slower to be able to stop in the same distance as on a dry road. Wet roads can double stopping distance. Reduce speed by about one-third (e.g., slow from 55 to 35 mph) on a wet road. On packed snow, reduce speed by half or more. If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so.

Prev
Next
If the roadway surface is icy, how much should you reduce your speed?
  • During icy conditions, stop immediately to avoid loss of control
  • Maintain current speed in order to avoid a rear-end collision
  • Reduce speed by 1/2
  • Reduce speed to a crawl and stop driving as soon as you can safely do so

Quote From The CDL Manual:

If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so.

Prev
Next
While on wet roads, how much should you reduce your speed?
  • Maintain regular speeds to avoid being rear-ended
  • Reduce speed by about 1/4
  • Reduce speed by about 1/2
  • Reduce speed by about 1/3

Quote From The CDL Manual:

It will take longer to stop and be harder to turn without skidding when the road is slippery. You must drive slower to be able to stop in the same distance as on a dry road. Wet roads can double stopping distance. Reduce speed by about one-third (e.g., slow from 55 to 35 mph) on a wet road. On packed snow, reduce speed by half or more. If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so.

Prev
Next
Why are roadways more slippery immediately after it begins to rain?
  • Water mixes with oil left on the road by vehicles
  • All of these are correct
  • Tires have to adjust to the wet conditions
  • It takes time for the roadway surface to absorb water

Quote From The CDL Manual:

Right after it starts to rain, the water mixes with oil left on the road by vehicles. This makes the road very slippery. If the rain continues, it will wash the oil away.

Prev
Next
When driving on packed snow, how much should you reduce your speed?
  • Reduce speed by about 1/8
  • Maintain your speed to avoid being rear-ended
  • Reduce speed by about 1/4
  • Reduce speed by about 1/2 or more

Quote From The CDL Manual:

It will take longer to stop and be harder to turn without skidding when the road is slippery. You must drive slower to be able to stop in the same distance as on a dry road. Wet roads can double stopping distance. Reduce speed by about one-third (e.g., slow from 55 to 35 mph) on a wet road. On packed snow, reduce speed by half or more. If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so.

Prev
Next
Which of the following are signs of potential slick spots on the roadway?
  • Bridges
  • Melting ice
  • Shaded areas
  • All of these are signs a road could be slippery

Quote From The CDL Manual:

Sometimes it is hard to know if the road is slippery. Following are signs of slippery roads:

  • Shaded areas - Shady parts of the road will remain icy and slippery long after open areas have melted.
  • Bridges - When the temperature drops, bridges will freeze before the road will. Be especially careful when the temperature is close to 32 degrees F.
  • Melting ice - Slight melting will make ice wet. Wet ice is much more slippery than ice that is not wet.
  • Black ice - Black ice is a thin layer that is clear enough that you can see the road underneath it. It makes the road look wet. Any time the temperature is below freezing and the road looks wet, watch out for black ice.
  • Vehicle icing - An easy way to check for ice is to open the window and feel the front of the mirror, mirror support or antenna. If there is ice on them, the road surface is probably starting to ice up.
  • Just after rain begins - Right after it starts to rain, the water mixes with oil left on the road by vehicles. This makes the road very slippery. If the rain continues, it will wash the oil away.
Prev
Finish
Please select an option
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