Construction Zone Traffic Control (C-31) · Lesson 2 of 6

Freeway Lane Closure Length: Signs, Taper and Buffer

"Freeway Lane Closure Length: Signs, Taper and Buffer" is lesson 2 of 6 in the Construction Zone Traffic Control (C-31) Learning Hub. It opens with "A Lane Closure Is a Chain of Distances" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. A Lane Closure Is a Chain of Distances
  2. Advance Warning Sign Spacing (T9 Table 3)
  3. Taper and Buffer Space (T9 Tables 1 and 2)
  4. Add It Up for the Closure Length
  5. Check the T10 Notes Before You Set Up

The worked example in the course applies this lesson to a realistic job in 5 steps, from "Advance warning signs" through "Re-check if the grade is steep".

What you'll be able to do

  • Explain the main idea of "Freeway Lane Closure Length: Signs, Taper and Buffer" in plain language you can use on the exam.
  • Apply this step with confidence: "Taper and Buffer Space (T9 Tables 1 and 2)".
  • Apply this step with confidence: "Add It Up for the Closure Length".
  • Apply this step with confidence: "Check the T10 Notes Before You Set Up".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Lane Closure Length: Signs, Taper, BufferFREEWAY, ONE LANE CLOSED, 65 MPH, LEVEL ROAD (not to scale)WORKC = 2,640 ftB = 1,500 ftA = 1,000 ftL = 780D = 6453rd sign2nd sign1st signtaper + arrowbufferAREADistances: Plan T9 Tables 1-3; layout: Plan T10ADD THE PIECES (level road)Signs: 2,640 + 1,500 + 1,000 = 5,140 ftTaper: L = 12 x 65 = 780 ftBuffer D (Table 2, 65 mph) = 645 ft5,140 + 780 + 645= 6,565 ft (1.24 mi)IF SUSTAINED -6% DOWNGRADE(steeper than -3%, longer than 1 mile)Buffer D = 728 ft (Table 2, -6%)5,140 + 780 + 728 = 6,648 ftURBAN 35 MPH (250 ft per sign):750 + 245 + 250 = 1,245 ftA, B, C = 250 ft each (T9 Table 3)65 mph, one lane: 6,565 ft from first sign to work area (1.24 mi)One flashing arrow sign per closed lane, Type I (Plan T10 note 8)Source: 2025 Caltrans Standard Plans T9 (Tables 1-3) and T10; CA MUTCD 2026 Section 6B.08CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: A Lane Closure Is a Chain of Distances

From the driver's side, a lane closure on a freeway is a sequence: advance warning signs, then the arrow board and merging taper, then a buffer space, then the work area. 2025 Caltrans Standard Plan T10 draws that layout for freeways and expressways, and Standard Plan T9 supplies three tables that put numbers on it: Table 1 (taper length and device spacing), Table 2 (buffer space and flagger station spacing) and Table 3 (advance warning sign spacing). CA MUTCD 2026 Section 6B.08 says that on State highways the Standard Plans T9 through T27 should be used.

Step 2: Advance Warning Sign Spacing (T9 Table 3)

Table 3 gives three distances, A, B and C. A is from the start of the taper back to the first sign, B is from the first sign to the second, and C is from the second to the third. For an expressway or freeway they are 1,000, 1,500 and 2,640 feet. For other roads: urban 25 mph or less is 100 feet each; urban more than 25 up to 40 mph is 250 feet each; urban more than 40 mph is 350 feet each; rural is 500 feet each. The table notes say the distances are approximate guidance and may be adjusted by the Engineer for field conditions. CA MUTCD 2026 Table 6B-1 prints a different urban breakdown (for example 35 mph is 200 feet), so use the table your contract or agency names.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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