7CDLFree CDL permit study for every state
Content preview, before public launch
Course › General Knowledge

Managing space ahead, behind and to the sides

General Knowledge3 minManual section 2.7.1–2.7.3

Space all around your vehicle gives you time to think and act when something goes wrong. Big vehicles take up more space and need more space to stop and turn. This lesson covers following distance, tailgaters, staying centered and avoiding driving alongside others.

Space ahead is the most important (2.7.1)

Of all the space around you, the space ahead — the space you are driving into — is the most important.

Crash reports show that the vehicle trucks and buses hit most often is the one in front of them, and the most frequent cause is following too closely. A smaller vehicle ahead can probably stop faster than you can.

How much following distance?

Rule: at speeds below 40 mph, keep at least 1 second for each 10 feet of vehicle length. Above 40 mph, add 1 second.

  • 40-foot vehicle: 4 seconds below 40 mph, 5 seconds above 40 mph.
  • 60-foot vehicle: 6 seconds below 40 mph, 7 seconds above 40 mph.

How to measure: wait until the vehicle ahead passes a clear landmark (a shadow, a pavement marking). Count “one thousand-and-one, one thousand-and-two…” until you reach the same spot. Compare your count to the rule.

Example: in a 40-foot truck you count only 2 seconds — you are too close. Drop back and count again until you have 4 seconds (5 over 40 mph). On slippery roads you need much more space.

Space behind (2.7.2): stay right and handle tailgaters

You cannot stop others from following too closely, but you can make it safer.

Stay to the right. Heavy vehicles are often tailgated when they cannot keep up with traffic, especially uphill. If a heavy load slows you, stay in the right lane if you can. Going uphill, do not pass another slow vehicle unless you can get around quickly and safely.

You are often tailgated when you are traveling slowly (drivers trapped behind follow closely) and in bad weather (many car drivers follow big vehicles closely when it is hard to see ahead). In a large vehicle it can be hard to see that someone is close behind.

If you are tailgated:

  • Avoid quick changes. Signal early and slow down very gradually.
  • Increase your following distance. More space ahead means fewer sudden moves, and it makes it easier for the tailgater to pass you.
  • Do not speed up. It is safer to be tailgated at a low speed than a high one.
  • Avoid tricks. Do not turn on your taillights or flash your brake lights to warn them off.

Space to the sides (2.7.3)

Commercial vehicles are wide and use most of a lane. Manage the little side space you have by keeping centered in your lane and avoiding driving alongside others.

Stay centered to keep safe clearance on both sides; a wide vehicle has little room to spare.

Two dangers of traveling next to others: another driver may change lanes suddenly and turn into you, and you may be trapped when you need to change lanes.

Find an open spot away from other traffic. In heavy traffic, keep as much space as possible, and drop back or pull forward so you are sure the other driver can see you.

Strong winds make it hard to stay in your lane. It is usually worse for lighter vehicles and can be especially bad coming out of tunnels. Do not drive alongside others if you can avoid it.

References and scope

The topic reference is listed below. Sources support verification; the lesson itself is here. The current content needs technical and language review before public launch.

Manual reference: 2.7.1–2.7.3

Official CDL handbook · Utah ↗StatesOur editorial approach

Put it into practice

Educational questions with explanations. The answer review also works without the interactive quiz.

Preparing your questions…

Review questions with answers

  1. Of all the space around your vehicle, which is the most important?
    1. Space behind
    2. Space to the right
    3. Space ahead
    4. Space overhead
    Show answer
    Space ahead

    The space ahead — the space you drive into — is the most important.

  2. According to crash reports, what vehicle do trucks and buses most often hit?
    1. The vehicle in front of them
    2. Vehicles turning left
    3. Parked vehicles
    4. Vehicles in the next lane
    Show answer
    The vehicle in front of them

    The vehicle ahead is hit most often, usually from following too closely.

  3. Below 40 mph, how much following distance should you keep?
    1. 2 seconds for any vehicle
    2. 1 second for each 20 feet of length
    3. 3 seconds plus 1 for each trailer
    4. At least 1 second for each 10 feet of vehicle length
    Show answer
    At least 1 second for each 10 feet of vehicle length

    The rule is 1 second per 10 feet of length below 40 mph.

  4. You drive a 40-foot vehicle at 55 mph. How many seconds of following distance do you need?
    1. 4 seconds
    2. 5 seconds
    3. 6 seconds
    4. 3 seconds
    Show answer
    5 seconds

    40 feet = 4 seconds, plus 1 second above 40 mph = 5 seconds.

  5. You drive a 60-foot rig at 30 mph. How many seconds of following distance do you need?
    1. 4 seconds
    2. 7 seconds
    3. 6 seconds
    4. 5 seconds
    Show answer
    6 seconds

    60 feet = 6 seconds below 40 mph (7 above 40 mph).

  6. How do you measure your following distance?
    1. Count seconds from when the vehicle ahead passes a landmark until you reach it
    2. Count the car lengths between you
    3. Use the odometer
    4. Estimate by the size of the vehicle in your windshield
    Show answer
    Count seconds from when the vehicle ahead passes a landmark until you reach it

    Pick a landmark and count “one thousand-and-one…” until you reach it.

  7. A smaller vehicle ahead of you can usually stop:
    1. More slowly than you
    2. At the same distance as you
    3. Only with ABS
    4. Faster than you
    Show answer
    Faster than you

    Smaller vehicles can probably stop faster, so following too closely can cause a crash.

  8. A heavy load is slowing you down on an uphill grade. What should you do?
    1. Move to the left lane
    2. Stay in the right lane if you can
    3. Pass slower trucks whenever possible
    4. Turn on your high beams
    Show answer
    Stay in the right lane if you can

    Stay right when slow; do not pass uphill unless you can do it quickly and safely.

  9. You are being tailgated. What should you do?
    1. Speed up to get away
    2. Flash your brake lights to warn them
    3. Increase your following distance and avoid quick changes
    4. Turn on your taillights and brake suddenly
    Show answer
    Increase your following distance and avoid quick changes

    Open space ahead, slow gradually, and do not speed up or use tricks.

  10. When are you most likely to be tailgated?
    1. When traveling slowly or in bad weather
    2. When driving at the speed limit on dry roads
    3. When parked
    4. When driving in the right lane at night only
    Show answer
    When traveling slowly or in bad weather

    Drivers follow closely behind slow vehicles and in bad weather.

  11. It is safer to be tailgated at a high speed than at a low speed.
    1. True
    2. False
    Show answer
    False

    False. It is safer to be tailgated at a low speed, so do not speed up.

  12. What are the two dangers of traveling alongside other vehicles?
    1. Wind noise and glare
    2. A driver may change lanes into you, and you may be trapped when you need to change lanes
    3. Higher fuel use and tire wear
    4. Mirror vibration and dust
    Show answer
    A driver may change lanes into you, and you may be trapped when you need to change lanes

    Drivers may turn into you, and you may have no escape when you need to change lanes.

  13. If you must travel near other vehicles in heavy traffic, you should:
    1. Drop back or pull forward so the other driver can see you
    2. Stay directly beside them
    3. Follow them very closely
    4. Drive on the lane line
    Show answer
    Drop back or pull forward so the other driver can see you

    Keep as much space as possible and make sure other drivers can see you.

  14. Strong side winds are often especially bad:
    1. At night
    2. On uphill grades
    3. Coming out of tunnels
    4. In heavy traffic
    Show answer
    Coming out of tunnels

    Winds can be especially bad coming out of tunnels, and worse for lighter vehicles.

  15. Why should you keep your vehicle centered in your lane?
    1. To make it easier for cars to pass on the shoulder
    2. To reduce tire wear
    3. To use less fuel
    4. To keep safe clearance on both sides
    Show answer
    To keep safe clearance on both sides

    A wide vehicle has little room to spare; centering keeps clearance on each side.

  16. Going uphill behind another slow vehicle, you should pass:
    1. Always, to keep traffic moving
    2. Only if you can get around quickly and safely
    3. Never, under any condition
    4. Only on the right shoulder
    Show answer
    Only if you can get around quickly and safely

    Do not pass uphill unless you can get around quickly and safely.