Road Signs: Sign Shapes

19 questions in the bank cover this topic. Everything below is drawn from the sources those questions cite.

Sources: MUTCD 11th Ed. Section 2B.04, MUTCD 11th Ed. Section 2B.05, MUTCD 11th Ed. Table 2A-1

What you need to know

Table 2A-1 reserves the octagon exclusively for the STOP sign.

Because no other sign may be that shape, the outline alone identifies it even when the face is obscured by snow or dirt.

Octagon* Stop (R1-1)**

* This shape shall be limited exclusively to the sign(s) indicated.

MUTCD 11th Ed. Table 2A-1

Table 2A-1 reserves the downward-pointing equilateral triangle exclusively for YIELD.

Like the octagon, the shape alone carries the message.

Equilateral Triangle (downward-pointing)* Yield (R1-2)**

MUTCD 11th Ed. Table 2A-1

Table 2A-1 reserves the pennant exclusively for the No Passing Zone sign.

It is mounted on the LEFT side of the road, which is unusual and is a deliberate cue.

Pennant (Isosceles Triangle with longer axis horizontal, pointed right)* No Passing Zone (W14-3)**

MUTCD 11th Ed. Table 2A-1

Table 2A-1 reserves the circle exclusively for the Grade Crossing Advance Warning sign, the round yellow sign with a black X and RR that warns of railroad tracks ahead.

Circle* Grade Crossing Advance Warning (W10-1)**

MUTCD 11th Ed. Table 2A-1

Table 2A-1 reserves the crossbuck exclusively for the Grade Crossing sign at the crossing itself, R15-1.

The MUTCD also forbids mounting a different shape on its back where that would obscure it.

Crossbuck (two rectangles in a perpendicular "X" configuration)* Grade Crossing (R15-1)**

MUTCD 11th Ed. Table 2A-1

Table 2A-1 assigns the upward-pointing pentagon to the School sign, with squared bottom corners, and to the County Route marker, with tapered lower sides.

Pentagon (upward-pointing)* School (S1-1) (squared bottom corners)**

MUTCD 11th Ed. Table 2A-1

Table 2A-1 assigns the diamond to the warning series.

A diamond tells you a condition lies ahead; it does not impose a legal requirement the way a regulatory sign does.

Diamond Warning Series

MUTCD 11th Ed. Table 2A-1

Table 2A-1 assigns the trapezoid to recreational and cultural interest area guide signs, and to the National Forest Route marker.

It pairs with the brown color the MUTCD gives those sites.

Trapezoid* Recreational and Cultural Interest Area Guide Series (isosceles or right-angled)

MUTCD 11th Ed. Table 2A-1

Table 2A-1 shows the rectangle used across the regulatory, guide and warning series.

Because it is not exclusive, you must read a rectangular sign's color and legend to know what it is.

Rectangle (including square) Regulatory Series

Rectangle (including square) Guide Series***

MUTCD 11th Ed. Table 2A-1

The single asterisk in Table 2A-1 means the shape is limited exclusively to the signs indicated, and the double asterisk means that sign must be exclusively the shape shown.

So the octagon can only be a STOP sign, and a STOP sign can only be an octagon. The exclusivity runs both ways, which is what lets a driver identify the sign by outline alone.

* This shape shall be limited exclusively to the sign(s) indicated.

** This sign shall be exclusively the shape shown.

MUTCD 11th Ed. Table 2A-1

The note to Table 2A-1 prohibits modifying standardised designs to accommodate a different shape except as the Manual itself provides.

Where space is tight the Manual offers other remedies, such as separate mountings or a greater mounting height.

Note: Signs with standardized designs shall not be modified to accommodate a different

shape except as provided in this Manual.

MUTCD 11th Ed. Table 2A-1

The MUTCD offers remedies that preserve the outline: separate mountings, a larger primary sign so the rear-mounted one does not protrude past its edge, or a greater mounting height so the second sign hangs below.

What it does not permit is losing the exclusive shape. Either keeps the exclusive shape readable.

Install the signs on separate mountings to maintain the exclusive shape.

Increase the size of the sign with the exclusive shape so the sign installed on the back does not obscure

MUTCD 11th Ed. Table 2A-1

MUTCD 2B.04 ties it to a full stop being ALWAYS required.

If stopping is only sometimes necessary, a YIELD sign is the correct device. The determination is made for that approach specifically.

When it is determined that a full stop is always required on an approach to an intersection, a STOP (R1-1) sign (see Figure 2B-1) shall be used.

MUTCD 11th Ed. Section 2B.04

MUTCD 2B.04 prohibits secondary legends.

The sign's whole value is instant recognition, and extra words invite the driver to read rather than act.

Secondary legends shall not be used on STOP sign faces.

MUTCD 11th Ed. Section 2B.04

MUTCD 2B.04 prohibits it, and 2B.05 prohibits the same for YIELD.

A changeable display cannot reliably reproduce the exclusive shape and color that make these signs recognisable.

The STOP sign shall not be displayed using a changeable message sign.

MUTCD 11th Ed. Section 2B.04

MUTCD 2B.04 requires the ALL-WAY plaque in red and white below each STOP sign.

Knowing this tells you whether cross traffic is also stopping. White legend and border on red.

At intersections where all approaches are controlled by STOP signs (see Section 2B.12), an ALL-WAY (R1-3P) supplemental plaque (see Figure 2B-1) shall be mounted below each STOP sign. The ALL-WAY plaque shall have a white legend and border on a red background.

MUTCD 11th Ed. Section 2B.04

MUTCD 2B.04 prohibits them.

ALL-WAY is the only approved plaque, so a driver never has to work out whether a number refers to approaches, lanes or something else.

Supplemental plaques with legends such as 2-WAY, 3-WAY, 4-WAY, or other numbers of ways shall not be used with STOP signs.

MUTCD 11th Ed. Section 2B.04

MUTCD 2B.05 defines it as yielding right-of-way, and notes it applies at intersections and where a two-way approach meets a one-way section such as a narrow bridge or underpass.

The YIELD sign requires road users to yield the right-of-way to other traffic on certain approaches to an intersection or on a two way approach to a one way section of roadway, such as a narrow bridge or underpass.

MUTCD 11th Ed. Section 2B.05

MUTCD 2B.05 requires slowing as the default and stopping when necessary.

In a loaded commercial vehicle that distinction matters, because arriving too fast to stop leaves you no option. And stop when necessary to avoid interfering with conflicting traffic.

Vehicles controlled by a YIELD sign need to slow down to a speed that is reasonable for the existing conditions or stop when necessary to avoid interfering with conflicting traffic.

MUTCD 11th Ed. Section 2B.05

Check yourself

• What sign or series uses the octagon?

• What sign or series uses the downward-pointing equilateral triangle?

• What sign or series uses the pennant, an isosceles triangle with its longer axis horizontal, pointed right?

• What sign or series uses the circle?

• What sign or series uses the crossbuck, two rectangles in a perpendicular X?

• What sign or series uses the upward-pointing pentagon?

• What sign or series uses the diamond?

• What sign or series uses the trapezoid?

• Which shape is used for the Regulatory, Guide AND Warning series, so the shape alone does not identify the sign type?

• What is the meaning of an asterisk beside a shape in the sign table?

• May a standard sign be reshaped to fit an unusual location?

• What should you expect when a second sign would obscure a STOP sign?

• When will you meet a STOP sign rather than a YIELD sign?

• May extra wording be added to the face of a STOP sign?

• May a STOP sign be shown to you on a changeable message sign?

• How do you know an intersection requires every approach to stop?

• Are 2-WAY, 3-WAY or 4-WAY plaques permitted with a STOP sign?

• What must you do at a YIELD sign?

• What is required of you when you face a YIELD sign?

Answers are in the practice test for this topic.