2005 Model Commercial Driver’s License Manual 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."  Speeding traffic is the number one cause of injury  and death in roadway work zones. Observe the  posted speed limits at all times when approaching  and driving through a work zone. Watch your  speedometer, and don’t allow your speed to creep  up as you drive through long sections of road  construction. Decrease your speed for adverse  weather or road conditions. Decrease your speed  even further when a worker is close to the roadway.  To be a safe driver, you need space all around your  vehicle. When things go wrong, space gives you  time to think and to take action.  To have space available when something goes  wrong, you need to manage space. While this is  true for all drivers, it is very important for large  vehicles. They take up more space and they  require more space for stopping and turning.  Of all the space around your vehicle, it is the area  ahead of the vehicle--the space you're driving into - -that is most important.  The Need for Space Ahead.  You need space  ahead in case you must suddenly stop. According  to accident reports, the vehicle that trucks and  buses most often run into is the one in front of  them. The most frequent cause is following too  closely. Remember, if the vehicle ahead of you is  smaller than yours, it can probably stop faster than  you can. You may crash if you are following too  closely.  How Much Space?  How much space should you  keep in front of you? One good rule says you need  at least one second for each 10 feet of vehicle  length at speeds below 40 mph. At greater speeds,  you must add 1 second for safety. For example, if  you are driving a 40-foot vehicle, you should leave  4 seconds between you and the vehicle ahead. In a  60-foot rig, you'll need 6 seconds. Over 40 mph,  you'd need 5 seconds for a 40-foot vehicle and 7  seconds for a 60-foot vehicle. See Figure 2.12.  To know how much space you have, wait until the  vehicle ahead passes a shadow on the road, a  pavement marking, or some other clear landmark.  Then count off the seconds like this: "one  thousand- and-one, one thousand-and-two" and so  on, until you reach the same spot. Compare your  count with the rule of one second for every ten feet  of length. These questions may be on the test. If you can't  answer them all, re-read subsections 2.4, 2.5, and  2.6. Subsections 2.4, 2.5, and 2.6  Test Your Knowledge  2.7.1 – Space Ahead  2.6.7 – Roadway Work Zones  2.7 – Managing Space  1.  How far ahead does the manual say you should  look?  2.  What are two main things to look for ahead?  3.  What's your most important way to see the  sides and rear of your vehicle?  4.  What does "communicating" mean in safe  driving?  5.  Where should your reflectors be placed when  stopped on a divided highway?  6.  What three things add up to total stopping  distance?  7.  If you go twice as fast, will your stopping  distance increase by two or four times?  8.  Empty trucks have the best braking. True or  False?  9.  What is hydroplaning?  10. What is "black ice”?  Section 2 – Driving Safely  Page 2-16