If you had a freeway billboard, what would it say?

Both lanes are used fully up to the merge point!

• At the point where one lane ends, drivers take turns merging:
  • One car from the left lane
  • One car from the right lane
• Just like the teeth of a zipper coming together.

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When to Use It

✔ Heavy traffic
✔ Stop-and-go or slow-moving conditions
✔ Clearly marked lane closures (“Lane Ends Ahead”)

🚫 Not necessary in light traffic (early merging works fine when there’s plenty of space)

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Why It Works

Traffic studies show zipper merging:

• Reduces queue length by up to ~40%
• Prevents one lane from backing up excessively
• Reduces rear-end collisions
• Keeps traffic flowing more evenly

Early merging in heavy traffic causes:

• Long backups in one lane
• Aggressive behavior
• Lane blocking and sudden braking

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Driver in the Ending Lane

1. Stay in your lane until the merge point.
2. Match the speed of traffic.
3. Signal early.
4. At the merge point, move smoothly into the open lane behind one vehicle.
5. Do not stop unless traffic is stopped.

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Driver in the Through Lane

1. Expect cars to merge at the end.
2. Leave one car length of space.
3. Maintain a steady speed.
4. Allow one vehicle in, then continue.
5. Do not block the ending lane.

Blocking is unsafe and often illegal.

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Common Myths (and the Truth)

❌ “Using the open lane until the end is cutting in line”
✅ It’s the intended design in heavy traffic.

❌ “Merging early is more polite.”
✅ Early merging actually makes congestion worse when traffic is heavy.

❌ “I should stop them from merging”
✅ Lane blocking increases crash risk and road rage.

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Key Rule to Remember

Early merge in light traffic.
Zipper merge in heavy traffic.