Questions about the q&a from the practice tests

I start CDL class next week, currently I'm going through the tests and would like some clarification.

• You are driving an 40 foot vehicle at 45 mph. What is the least amount of space, in seconds, you should keep in front of your vehicle? When you are traveling under 40 mph, you should follow other vehicles with a distance of 1 second for every 10 feet of your vehicle length? How do you realistically calculate these distances? I'm having trouble picturing what "seconds" looks like as a distance.

• If you are being tailgated, you should increase your following distance and avoid quick lane or speed changes? Unless you're pulling an empty flatbed, how do you know if you're being tailgated if you can't see the car behind you?

• How can an engine retarder cause a truck to skid on slippery roads?

• How can the truck get stuck in neutral if the driver downshifts while driving down a mountain?

 

Is stab breaking something that is used only in trucks that don't have ABS?

 

Look at a sign or landmark a distance down the road, then begin counting: 1 one thousand, 2 one thousand, etc. When the truck reaches that point in the road, that's roughly the amount of seconds away you are. Use this system to gauge and estimate following distance.

 

You should be constantly visually scanning in 360 degrees all around the truck while traveling. This includes checking both mirrors every 3-6 seconds. During mirror checking, you should be able to tell at some point if you are being tailgated when the offending vehicle drifts slightly within the lane or the trailer you're pulling does so. It's all about being constantly aware of all of your surroundings and identifying and anticipating potential traffic hazards. You probably will be able to see the vehicle approaching from the rear, then disappearing into your blind spot.

 

When an engine retatder(jake brake) engages, it uses the drive tires to slow the vehicle. This can cause loss of control because the driver cannot regulate the amount of braking power with the service(pedal) brakes. A sudden slowdown of the vehicle caused by engine braking can cause the vehicle to go into a skid on slick road surfaces(this includes wet roads as well).

 

In a CMV with a manual transmission, the gears are not synchronized with the engine. This means that to upshift or downshift, the driver must match the engine RPM's with the RPM's of the transmission. This can be done by braking or acceleration respectively. If the truck is rapidly accelerating down a steep grade, the transmission RPM's will want to exceed those of the engine. This can make it very difficult or impossible to match the RPM's of both to downshift unless there is braking. Braking must be minimized on downgrades due to the possibility of overheating the brakes, which could cause the brakes to fail.
The general rule is to descend a steep grade in a lower gear than you used to climb with...
Just grab the gear before you begin your descent.

 

Yes.

 

How common is it for trucks/cabs to not have ABS?

 

Not common at all now, I think everything after 2001¿ Has to have abs

 

Empty trucks may require longer stopping distances than full ones. Why? Wouldn't the increased weight/mass of a full truck need require more breaking power and distance to stop it?