Speed, following space and zipper merging

Key points

1. Crashes are a leading cause of death for people ages 16 to 25 in Washington.

   Source: PDF page 60

   “In Washington, vehicle crashes are a leading causes of death for people ages 16 to 25.”
   Washington Driver Guide (plain-text version), PDF page 60

2. Speed limits are the maximum legal speed under ideal conditions, and you must slow down when conditions are poor.

   Source: PDF page 63

   “Speed limits indicate the maximum speed legal under ideal conditions. Washington law also requires you to drive at speeds that are safe for current road conditions.”
   Washington Driver Guide (plain-text version), PDF page 63

3. Excessive speed reduces the effectiveness of seat belts.

   Source: PDF page 62

   “Seat belts are designed to protect you in a crash, but their effectiveness decreases at higher speeds.”
   Washington Driver Guide (plain-text version), PDF page 62

4. Near other vehicles, leave at least twice the length of your vehicle between you and the vehicle ahead.

   Source: PDF page 63

   “it’s important to leave a distance that’s at least twice the length of your vehicle between you and the vehicle ahead.”
   Washington Driver Guide (plain-text version), PDF page 63

5. Drivers already on the interstate have the right of way, so you may need to adjust your speed to merge.

   Source: PDF page 64

   “Drivers already on the interstate have the right-of-way, so creating space to merge might require you to adjust your speed, faster or slower.”
   Washington Driver Guide (plain-text version), PDF page 64

6. Zipper merging improves traffic flow by 60 percent.

   Source: PDF page 64

   “Zipper merging is a technique that: Improves traffic flow by 60 percent.”
   Washington Driver Guide (plain-text version), PDF page 64

7. In a zipper merge, use both lanes until the merge point, then take turns.

   Source: PDF page 64

   “Continue using both lanes until you reach the designated merge area. Take turns.”
   Washington Driver Guide (plain-text version), PDF page 64

8. Practice judging space by picking a marker you think is 15 seconds ahead and counting.

   Source: PDF page 64

   “Pick out a marker, such as a road sign or utility pole, that you think is 15 seconds ahead of your vehicle.”
   Washington Driver Guide (plain-text version), PDF page 64

9. When turning in front of oncoming traffic, remember approaching traffic has the right of way.

   Source: PDF page 65

   “Remember approaching traffic has the right-of-way.”
   Washington Driver Guide (plain-text version), PDF page 65

Numbers to know

3 questions from the Washington practice test

1. 1. When road conditions are poor, how should a Washington driver use the posted speed limit?

   1. Treat it as a minimum and accelerate to reach it
   2. Treat it as a maximum and reduce speed when conditions require
   3. Ignore it completely whenever rain begins
   4. Use it unchanged because conditions never affect legal speed
   Show answer

   Treat it as a maximum and reduce speed when conditions require. Washington describes a speed limit as the maximum legal speed under ideal conditions, while also requiring a speed that is safe for current conditions. Rain, snow, fog, traffic, and limited visibility can require a slower pace. The choice calling the limit a minimum reverses its meaning, and completely ignoring the sign is unnecessary. The practical cue is maximum under ideal conditions, then adjust downward. A driver can be below the posted number and still be traveling too fast if the roadway or visibility makes stopping difficult.

2. 2. What minimum space does the Washington guide recommend between your vehicle and the vehicle ahead when driving near other vehicles?

   1. At least twice the length of your vehicle
   2. Exactly one vehicle length at all times
   3. A distance measured only by the car behind you
   4. One tire length regardless of speed
   Show answer

   At least twice the length of your vehicle. The guide recommends leaving a distance at least twice the length of your vehicle from the vehicle ahead. This provides room to respond if traffic changes or the lead driver brakes. The one tire length and fixed one vehicle length choices are smaller or unsupported distances, while the car behind you does not determine the space needed ahead. Use the size of your own vehicle as the reference, then leave at least two of those lengths. Increase the margin further when weather, darkness, congestion, or a vulnerable road user reduces your options.

3. 3. What should you do when traffic is moving slowly because a lane is closed?

   1. Merge immediately and block the ending lane
   2. Stop in the open lane until another driver waves you in
   3. Pass the line on the shoulder
   4. Use both lanes until the designated merge area, then take turns
   Show answer

   Use both lanes until the designated merge area, then take turns. Washington describes zipper merging for slow or stopped traffic caused by a lane closure. Continue in your lane until the marked merge area, then alternate with vehicles from the other lane. Merging at the first sight of a closure can leave unused roadway and create a less predictable line. The shoulder is not a passing lane, and stopping in the open lane creates a new obstruction. Keep a steady pace, signal your intent, and allow one vehicle from the ending lane to enter in turn.

Source: the Washington Driver Guide (plain-text version), Chapter 5: Hazards. This lesson is a plain English summary, not the law itself; where it differs, the manual and the statute govern. Last checked 2026-09-27.