MUTCD Glossary
Plain-English definitions of the MUTCD, traffic control, work zone, sign, device, pedestrian access, and permit terms used across this reference.
This glossary defines the traffic control terms you’ll meet on this site and on real projects — from MUTCD and sign types to temporary traffic control, work zones, pedestrian access routes, devices, and permits. Search for a term, jump to a letter, and follow the links to related signs or official MUTCD and Caltrans resources.
74 terms.
A
- AASHTO
- American Association of State Highway and Transportation Officials — publishes national design guides (such as the “Green Book”) that work alongside the MUTCD.
- Activity Area
- The part of a temporary traffic control zone where the work actually takes place; it contains the work space, the traffic space, and any buffer spaces.
- Related:Temporary Traffic Control (TTC)Buffer SpaceWork Space
- ADA
- Americans with Disabilities Act — federal civil-rights law that requires pedestrian facilities, including temporary routes through work zones, to remain accessible to people with disabilities.
- Related:PROWAGTemporary Pedestrian Access Route (TPAR)Curb Ramp
- Advance Warning Area
- The first section of a work zone that drivers reach, where signs tell them what to expect ahead. It usually begins with the “ROAD WORK AHEAD” (W20-1) sign.
- Related:Temporary Traffic Control (TTC)Sign SpacingRoad Work AheadW20-1 Road Work Ahead
- Arrow Board
- A trailer- or truck-mounted panel of lights that displays a flashing or sequencing arrow to direct drivers out of a closed lane. Also called an arrow panel.
- Related:Lane ClosureTaperChangeable Message Sign (CMS)
B
- Ballast
- Weight (such as sandbags) added to a portable sign stand or channelizing device so wind and passing traffic don’t knock it over.
- Barricade
- A portable device with retroreflective rails used to close or delineate a road or walkway. Types I and II are smaller advance/channelizing units; Type III is a full-width road-closure barricade.
- Related:Channelizing DeviceRoad ClosureDetectable EdgingRoad Closure Signs
- Breakaway Support
- A sign post or support designed to give way on impact, reducing injury when a vehicle strikes it.
- Buffer Space
- An open (unoccupied) area that separates traffic from the work space, or one traffic movement from another, giving an errant vehicle room to stop. May be longitudinal (lengthwise) or lateral (sideways).
- Related:Activity AreaTaperWork Space
C
- CA MUTCD California
- California’s edition of the MUTCD. It adopts the federal manual and adds state-specific changes, and it governs traffic control devices on California streets and highways.
- California note: The CA MUTCD is maintained by Caltrans and is the controlling standard for public roads in California, including local agency streets.
- Related:MUTCDCaltransCA MUTCD (Caltrans)
- Caltrans
- The California Department of Transportation — the state agency that maintains the CA MUTCD, sign specifications, and standard plans.
- Related:CA MUTCDStandard PlansSign SpecificationCaltrans Sign Charts
- Changeable Message Sign (CMS)
- An electronic sign that can display different word messages. A trailer-mounted version used in work zones is often called a Portable Changeable Message Sign (PCMS).
- Related:Arrow BoardWork Zone
- Channelizing Device
- Any device — cone, tubular marker, drum, vertical panel, or barricade — used to guide traffic and separate it from the work space.
- Related:ConeDrumDelineatorBarricadeTaper
- Cone
- A predominantly orange traffic cone used to channel traffic. Cones 28 inches or taller (often with a reflective collar) are used on higher-speed roads and at night.
- Related:Channelizing DeviceTubular Marker
- Conspicuity
- How easily a sign or device is noticed. Retroreflective sheeting, size, contrast, and placement all affect it.
- Related:RetroreflectivitySheeting
- Crashworthy
- A device or support that has been tested (per NCHRP 350 or MASH criteria) to behave predictably and reduce harm when struck by a vehicle.
- Related:Breakaway SupportBallast
- Curb Ramp
- The sloped connection between a sidewalk and the street that lets wheelchair users and others cross. Temporary routes through work zones must still provide an accessible way around obstacles.
- Related:ADATemporary Pedestrian Access Route (TPAR)PROWAG
D
- Delineator
- A retroreflective post or marker that shows the alignment of the roadway edge, especially at night or in bad weather.
- Related:Channelizing DeviceObject Marker
- Detectable Edging
- A continuous, firm bottom edge (such as a curb, rail, or barrier) that a person using a cane can detect, used to guide pedestrians safely along a temporary route.
- Related:Temporary Pedestrian Access Route (TPAR)ADASidewalk Closure
- Detour
- A signed alternate route that sends traffic around a closed road or work area and back to the original route.
- Related:Road ClosureGuide SignDetour Signs
- Drum
- A large, portable channelizing device (a plastic “barrel”) with retroreflective bands, used to guide traffic in higher-speed or longer-duration work zones.
- Related:Channelizing DeviceConeTaper
E
- Encroachment Permit California
- Written permission from the controlling agency to work within, or place anything in, the public right-of-way — for example to close a lane or open a trench.
- California note: In California, work in a state highway right-of-way requires a Caltrans encroachment permit; local streets are permitted by the city or county.
- Related:Public Right-of-Way (ROW)Traffic Control Plan (TCP)Jurisdiction
F
- FHWA
- Federal Highway Administration — the U.S. DOT agency that issues and maintains the national MUTCD.
- Related:MUTCDStandard Highway Signs (SHS)FHWA MUTCD
- Flagger
- A trained worker who uses a STOP/SLOW paddle (and sometimes a flag) to control traffic through a work zone, typically where one lane is shared by two directions.
- Related:Flagging StationTemporary Traffic Control (TTC)Pilot Car
- Flagging Station
- The location where a flagger stands to control traffic, chosen so approaching drivers have enough sight distance to stop safely.
- Related:FlaggerSight Distance
- Fluorescent Orange
- The bright orange background color required for most temporary traffic control (work zone) warning signs, chosen for daytime conspicuity.
- Related:Warning SignWork ZoneSheetingTemporary Traffic Control Signs
- Fluorescent Yellow-Green
- A bright yellow-green background color used for pedestrian, bicycle, and school warning signs to make these vulnerable-user warnings stand out.
- Related:Warning SignSign FaceWarning Signs
G
- Guide Sign
- A sign that gives direction, distance, destinations, services, or route information. Guide signs are usually green, blue, or brown.
- Related:Regulatory SignWarning SignDetourGuide Signs
J
- Jurisdiction
- The agency that owns and controls a road (state, county, or city) and therefore sets its permit and traffic control requirements.
- Related:Encroachment PermitPublic Right-of-Way (ROW)Agency
L
- Lane Closure
- Temporarily taking a travel lane out of service for work, guided by advance signs, a taper of channelizing devices, and often an arrow board.
- Related:TaperArrow BoardShoulder ClosureBuffer Space
- Legend
- The message on a sign — the letters, numerals, symbols, arrows, or borders — as opposed to the background.
- Related:Sign FaceSymbol SignWord Message Sign
- Longitudinal Buffer
- Buffer space measured along the direction of travel, placed between the end of a merging taper and the start of the work space.
- Related:Buffer SpaceTaper
M
- MASH
- Manual for Assessing Safety Hardware — the current crash-test standard (successor to NCHRP 350) that roadside and work-zone devices must meet.
- Related:CrashworthyNCHRP 350
- Mounting Height
- The vertical distance from the pavement or ground to the bottom of a sign. Typical minimums are about 7 feet in urban areas and 5 feet in rural areas.
- Related:Sign SupportSign Face
- MUTCD
- Manual on Uniform Traffic Control Devices — the national standard that defines how traffic signs, signals, and pavement markings look and where they go. States adopt it directly or with modifications.
- Related:CA MUTCDFHWAStandard Highway Signs (SHS)FHWA MUTCD
N
- NCHRP 350
- An older crash-test standard for roadside safety hardware, largely replaced by MASH for newly manufactured devices.
- Related:MASHCrashworthy
- Nominal Size
- The named, standard size of a sign (for example, a 30-inch STOP sign), from which the actual dimensions and legend layout are scaled.
- Related:Sign FaceMounting Height
O
- Object Marker
- A striped or patterned retroreflective marker (the OM series) that shows the location of an obstruction or the end of a roadway. Type 3 markers use diagonal black-and-yellow stripes.
- Related:DelineatorRetroreflectivityObject Markers (OM series)
P
- Pedestrian Access Route (PAR)
- The continuous, accessible path provided for pedestrians along or across a street. When work disrupts it, a temporary equivalent must be provided.
- Related:Temporary Pedestrian Access Route (TPAR)ADAPROWAG
- Pilot Car
- A lead vehicle that guides a queue of traffic through a long or complex one-lane work zone where flaggers alone can’t maintain control.
- Related:FlaggerLane Closure
- Plaque
- A small supplemental sign mounted with a primary sign to add information — such as a distance, an arrow, or “AHEAD.”
- Related:Sign FaceLegend
- PROWAG
- Public Right-of-Way Accessibility Guidelines — the accessibility rules for sidewalks, curb ramps, crossings, and pedestrian routes in the public right-of-way, including temporary ones.
- Related:ADAPedestrian Access Route (PAR)Public Right-of-Way (ROW)
- Public Right-of-Way (ROW)
- The publicly owned land set aside for a street and its sidewalks, shoulders, and utilities. Working in it generally requires a permit.
- Related:Encroachment PermitJurisdictionPROWAG
R
- Regulatory Sign
- A sign that tells road users what they must or must not do — such as STOP, YIELD, speed limits, or turn restrictions. Most are black and white or red and white.
- Related:Warning SignGuide SignRight-of-WayRegulatory Signs
- Retroreflectivity
- A sheeting property that sends a vehicle’s headlight beam back toward the driver, keeping signs and devices legible at night. The MUTCD sets minimum levels.
- Related:SheetingConspicuity
- Right-of-Way
- The right of one road user to proceed before another. Regulatory signs like STOP and YIELD assign it. (Not to be confused with the physical public right-of-way.)
- Related:Regulatory SignYield (R1-2)Stop (R1-1)
- Road Closure
- Fully closing a road to through traffic, marked with a Type III barricade and “ROAD CLOSED” signing, usually with a signed detour.
- Related:DetourBarricadeRoad ClosedRoad Closure Signs
- Road Work Ahead
- The W20-1 warning sign that opens most work zones, telling drivers that a work operation is on or near the road ahead.
- Related:Advance Warning AreaWork ZoneW20-1 Road Work Ahead
- Roll-Up Sign
- A flexible (usually vinyl) work-zone sign on a portable stand that can be rolled up for storage and transport; common for short-duration operations.
- Related:Sign SupportTemporary Traffic Control (TTC)
S
- Sheeting
- The retroreflective film applied to a sign face. Higher grades (high-intensity, diamond-grade) reflect more light and stay legible farther away at night.
- Related:RetroreflectivitySign FaceSubstrate
- Shoulder Closure
- Closing the paved shoulder for work while travel lanes stay open, marked with advance signs and channelizing devices.
- Related:Lane ClosureChannelizing Device
- Sidewalk Closure
- Temporarily closing a sidewalk for work. An accessible, signed alternate pedestrian route must be provided.
- Related:Temporary Pedestrian Access Route (TPAR)Detectable EdgingCrosswalk ClosurePedestrian & Sidewalk Closure Signs
- Sight Distance
- How far ahead a driver can see. Signs, flaggers, and tapers must be placed where drivers have enough sight distance to react and stop.
- Related:Flagging StationAdvance Warning Area
- Sign Face
- The front surface of a sign that carries the background color and the legend.
- Related:LegendSheetingSubstrate
- Sign Spacing
- The distance between advance warning signs, set by roadway type. The MUTCD uses spacing dimensions A, B, and C — shorter on low-speed streets, longer on freeways.
- Related:Advance Warning AreaSign Support
- Sign Specification
- The official drawing that gives a sign’s exact dimensions, colors, borders, and letter sizes. FHWA publishes these as Standard Highway Signs; Caltrans publishes California versions.
- Related:Standard Highway Signs (SHS)CaltransCaltrans Sign Specifications
- Sign Support
- The post, stand, or structure that holds a sign. Ground-mounted supports on the roadside are usually breakaway or crashworthy.
- Related:Breakaway SupportMounting HeightU-Channel Post
- Speed Limit (R2-1)
- The regulatory sign that posts the maximum (or minimum) legal speed for a section of road.
- Related:Regulatory SignR2-1 Speed Limit
- Standard Highway Signs (SHS)
- The FHWA publication of official sign layout drawings and dimensions that accompanies the MUTCD.
- Related:MUTCDSign SpecificationFHWA Standard Highway Signs
- Standard Plans California
- An agency’s standardized construction and traffic-handling drawings. Caltrans Standard Plans include typical work-zone layouts referenced on traffic control plans.
- California note: California traffic control plans frequently cite Caltrans Standard Plans (the T-series) for typical lane- and shoulder-closure layouts.
- Related:Traffic Control Plan (TCP)CaltransCaltrans Standard Plans
- Stop (R1-1)
- The red octagonal regulatory sign that requires every driver to come to a complete stop and yield before proceeding.
- Related:Regulatory SignRight-of-WayYield (R1-2)R1-1 Stop
- Substrate
- The rigid backing (such as aluminum) that a sign’s sheeting is applied to.
- Related:SheetingSign Face
- Symbol Sign
- A sign that conveys its message with a picture or symbol rather than words, so it can be understood quickly and across languages.
- Related:LegendWord Message Sign
T
- Taper
- A line of channelizing devices angled across the road to move traffic gradually out of its normal path — for example, to close a lane. Its length depends on speed and lane width.
- Related:Lane ClosureChannelizing DeviceBuffer Space
- Temporary Pedestrian Access Route (TPAR) California
- The accessible pedestrian path that must be provided and maintained when work affects a sidewalk or crosswalk, so people — including those with disabilities — can still get through safely.
- California note: California agencies commonly require a TPAR whenever a sidewalk or crosswalk is closed, with detectable edging and accessible signing.
- Related:Pedestrian Access Route (PAR)ADAPROWAGDetectable EdgingPedestrian & Sidewalk Closure Signs
- Temporary Traffic Control (TTC)
- The signs, markings, devices, and procedures used to move road users safely and efficiently through or around a work zone or incident.
- Related:Traffic Control Plan (TCP)Work ZoneActivity AreaAdvance Warning AreaTemporary Traffic Control Signs
- Traffic Control Plan (TCP) California
- The drawing that shows how traffic (and pedestrians) will be handled around a work area — sign callouts, spacing, tapers, devices, and phasing.
- California note: In California, a TCP is typically submitted with the encroachment permit application and must follow the CA MUTCD and applicable Caltrans Standard Plans.
- Related:Temporary Traffic Control (TTC)Standard PlansEncroachment Permit
- Tubular Marker
- A slim, vertical channelizing device with retroreflective bands, used where space is tight or to separate opposing flows.
- Related:ConeChannelizing Device
U
- U-Channel Post
- A common galvanized-steel sign post with a U-shaped cross-section, often installed as (or with) a breakaway base.
- Related:Sign SupportBreakaway Support
W
- Warning Sign
- A sign that alerts road users to a condition or hazard ahead so they can adjust. Most are yellow (or orange in work zones) diamonds with black legends.
- Related:Regulatory SignGuide SignFluorescent OrangeWarning Signs
- Word Message Sign
- A sign that uses words rather than a symbol to convey its message (for example, “ROAD WORK AHEAD”).
- Related:Symbol SignLegend
- Work Space
- The area within a work zone, closed to traffic, where workers, equipment, and materials are located.
- Related:Activity AreaBuffer SpaceWork Zone
- Work Zone
- An area of a road where construction, maintenance, or utility work affects normal traffic. Work zones are set up and signed using temporary traffic control.
- Related:Temporary Traffic Control (TTC)Activity AreaRoad Work AheadTemporary Traffic Control Signs
Y
- Yield (R1-2)
- The red-and-white triangular regulatory sign that requires drivers to slow, be ready to stop, and give the right-of-way to conflicting traffic or pedestrians.
- Related:Regulatory SignRight-of-WayStop (R1-1)R1-2 Yield
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