Diamond Road Signs
365 signsWarning · W series
A diamond warns of something ahead, like a curve, a crossing or road work. Yellow marks lasting conditions, orange marks work zones, and fluorescent yellow-green warns of people on foot or bike.
A road sign's shape tells drivers what kind of sign it is before they can read a word, even at night or from the back. The MUTCD sets nine shapes, and seven of them belong to certain signs only. Below is what each shape means, with links to our signs in each one.
Road Sign Shapes and Their Meanings
Each card shows one of our signs in that shape and where to find the rest.
Rectangular Road Signs
356 signsRules and guidance · squares included
The MUTCD counts every rectangle as one shape, squares included. Tall ones mostly state a rule, wide ones guide drivers or point the way, and squares carry symbol rules and plaques.
Octagon Signs
11 signsStop · R1-1
Eight sides mean stop, and the R1-1 is the only sign allowed to have them. From behind, the octagon still tells drivers on the cross street that the other road must stop.
Triangle
Yield · R1-2
Pointing down, the triangle means yield, and no other sign may use it. In much of Europe a triangle points up to warn of danger, so the direction of the point matters.
Pentagon
School and county route · S1-1, M1-6
Shaped like a house with square bottom corners, the S1-1 warns drivers of a school area or a school crossing. With its lower sides angled in, the same shape becomes the county route marker.
Pennant
No passing zone · W14-3
This sideways triangle, pointing right, marks the start of a no passing zone. It stands on the left side of the road, where a driver about to pass will see it.
Circle
Railroad ahead · W10-1
The round yellow sign with an X and two Rs stands before a railroad crossing so drivers can slow down and look for trains. No other road sign is round, so drivers know it on sight before they can read the letters.
Crossbuck
Railroad crossing · R15-1
Two white blades crossed in an X mark the crossing itself, where drivers must yield to trains. Where two or more tracks cross the road, a plaque below it shows the number of tracks.
Trapezoid
Recreation guide signs
The MUTCD keeps the trapezoid for some recreation and cultural interest area guide signs and for the National Forest route marker.
Road Sign Shape Questions
What shape is a warning sign?
Most warning signs are diamonds. A few are rectangles, such as the chevrons and large arrows posted at sharp curves, and two warnings have shapes of their own: the round railroad advance sign and the No Passing Zone pennant.
Can another sign be mounted on the back of a stop sign?
Yes, as long as it does not stick out past the edges and hide the octagon. The MUTCD asks the same for every reserved shape, and for the railroad crossbuck it is a firm rule. When the second sign is too big, put it on its own post, use a larger shaped sign, or mount the shaped sign higher so the other one fits below its bottom edge.
Does a sign's shape change with its size?
No. Each sign keeps the same shape in every size, so a 48" stop sign is simply a bigger octagon than a 30" one. Match the shape and code of the sign you are replacing, then pick the size the road calls for.
How do shape and color work together?
Shape tells drivers what kind of sign they are looking at, and color narrows the message, like red for stop or no entry and blue for motorist services. Our road sign colors page covers each color.