1. The Regulatory Baseline (MUTCD 11^th Edition)

• Daytime & low-speed roadways – minimum height 18 inches. Low-speed is typically considered roadways with speed limits of 40 mph or less.
• Nighttime use, or roadways with a speed limit of 45 mph or higher – minimum height 28 inches.
• Freeways, other high-speed highways, or when more conspicuous guidance is needed – minimum height 28 inches.
• Cones more than 36 inches in height require horizontal, circumferential, alternating orange and white retroreflective stripes that are 4 to 6 inches wide, with a minimum of two orange and two white stripes (top stripe orange).

Retroreflectivity Requirements

• Cones less than 28 inches: At least one 6-inch wide retroreflective band placed a minimum of 3 inches from the top.
• Cones 28 to 36 inches: A 6-inch wide white band located 3 to 4 inches from the top, and an additional 4-inch wide white band located approximately 2 inches below the 6-inch band.
• Cones more than 36 inches: As noted above, alternating orange and white stripes.

2. Why Some Agencies Prefer 36 Inches

3. When a 28-Inch Cone Is the Right Tool

• Urban streets with speeds ≤ 40 mph – suitable for lane closures, utility work, and short tapers.
• Daytime operations on low-volume or two-lane roads – lighter and easier to deploy for mobile crews.
• Parking lots, school zones, or special events – portable yet tall enough to guide pedestrians and vehicles.
• Night work on low-speed roads with proper retroreflective bands – must include the required two-band pattern (6″ + 4″ white).

4. When to Deploy 36-Inch Cones

• Speeds ≥ 45 mph (freeways, expressways, multilane arterials) – for better visibility and stability.
• Nighttime work on high-volume or high-speed roads – exceeds minimum requirements for safety.
• Long-term or multi-day closures – heavier design reduces need for frequent adjustments.
• Areas with heavy truck traffic, blind curves, or crests – provides extra conspicuity.
• Projects with stricter local mandates – verify with your state DOT (e.g., NCDOT mandates 36″ for freeways; Caltrans recommends for urban freeways).

5. Quick Decision Flow

1. Assess posted speed limit:
   • < 45 mph → consider 28″ as starting point.
   • ≥ 45 mph → default to 36″ for enhanced safety.
2. Day or night operations?
   • Night work requires at least 28″; prefer 36″ on high-speed roads for better visibility.
3. Job duration and exposure:
   • Short, mobile, low-speed daytime tasks → 28″.
   • Stationary, multi-day closures on busy roads → 36″.
4. Local specs override MUTCD minimums: Always review state DOT guidelines and contract documents.

6. Final Takeaways