Channelizing Devices & Arrow Boards
Channelizing devices guide traffic past the work. The C-31 exam tests their sizes, striping, spacing, and the right arrow-board mode.
Devices and dimensions
Cones: ≥ 18 in day/low-speed; ≥ 28 in freeway or night. Drums: ≥ 36 in, no metal, no ballast on top. Vertical panels: ≥ 24 in high, stripes slope down toward the side traffic passes. Barricades: Type 1 & 2 ≥ 24 in long, Type 3 ≥ 48 in — used to close a road.
Cones, drums, panels, and barricades all use alternating orange and white retroreflective stripes, and the diagonal stripes always slope downward toward the side traffic is to pass.
Spacing
Channelizing devices are spaced no more than 1 × the speed limit (in feet) on a taper, and no more than 2 × the speed limit (in feet) on a tangent. So at 30 mph, devices in the taper go no farther than 30 ft apart; on a 50 mph tangent, no farther than 100 ft.
Arrow boards
An arrow board’s elements are yellow. Use arrow or chevron mode only for a lane closure on a multilane road, and caution mode for shoulder or one-lane two-way work. An arrow board may show a closure but must never indicate a lane shift.
Practice: Channelizing Devices & Arrow Boards
Frequently asked
How tall must traffic cones be?
What are the rules for traffic control drums?
When is an arrow board used in arrow mode versus caution mode?
More C-31 Traffic Control topics
Planning & Estimating Traffic Control
C-31 study guide on planning a traffic control zone: the four TTC areas, taper-length formulas, buffer space, advance warning sign spacing, and estimating devices.
Read & practice →Notifications, Permits & Coordination
C-31 study guide on permits and coordination for traffic control work: encroachment permits, 811/USA excavation notice, agency and public notification, and closure windows.
Read & practice →Work-Zone Signs & Markings
C-31 study guide on work-zone signs: orange sign color, sign shapes, common MUTCD codes (W20-1, W20-7, W3-4, G20-2), nighttime retroreflectivity, and changeable message signs.
Read & practice →Flagging Operations
C-31 study guide on flagging: the STOP/SLOW paddle, paddle size, when a flag may be used, flagger signaling methods, and flagger station placement and night lighting.
Read & practice →Transportation & Training
C-31 study guide on transporting traffic control devices and training requirements: flagger training before assignment, what training covers, and where it is documented.
Read & practice →Worker Safety & PPE
C-31 study guide on work-zone worker safety: high-visibility apparel classes, OSHA accident-prevention sign colors, struck-by hazards and the Focus Four, and night-work lighting.
Read & practice →