Road signs play a crucial role in keeping motorists safe on city streets and highways. There are currently several hundred different variations out there. Therefore it’s vital to categorize them in such a way so that drivers can quickly see, interpret, and safely react to the information.
This is why the Federal Highway Administration (FHWA) created the Manual on Uniform Traffic Control Devices (MUTCD). It provides cities and states with standardization guidelines for all street and highway signs.
In addition to the messages and color, road sign shapes are designed to make them instantly recognizable to motorists. This shaves critical microseconds off the time it takes for a driver to interpret a sign and make a decision.
Read on to learn more about what road sign shapes indicate.
Why Road Signs Have Different Shapes
With so many signs on the road, it’s challenging for drivers to memorize all of them. This is why the MUTCD designated specific shapes to convey a specific message category.
For example, circular signs are relegated to railroad crossing safety information while diamond-shaped signs warn motorists of upcoming hazards.
Another critical reason why signs have specific shapes is due to potentially limited visibility. Dirt, snow, glare from the sun or any other environmental factors can limit motorists’ ability to quickly and accurately read the text on a sign. However, they can still make out the general shape, thereby giving them an important clue as to what lies ahead.
Examples of Road Signs and Their Meanings
Below, you’ll find a list of the various sign shapes along with some common examples and where you can find them.
Circle – Signs that are in the shape of a circle exclusively convey railroad crossing advance warning information. They’re typically found anywhere up to 1,000 yards out from a railroad crossing.
Diamond – Diamond-shaped signs can indicate a temporary or permanent warning sign. They’re often found in areas where motorists require advance notice of a change of driving conditions, such as merging lanes, hairpin curves, or upcoming twist in the road with a set speed limit.
Pentagon – Pentagon-shaped signs are often placed near schools and provide advance warning to motorists. School warning information isn’t limited to pentagons as other shapes also convey school-related information, such as the diamond-shaped “School Bus Stop Ahead” sign. If you see an inverted pentagon, it’s indicative of a county route marker.
Octagon – The octagon shape is exclusively used for stop signs. This is so that when motorists see an octagon-shaped sign, there’s no mistaking it for anything else. They’re found in places where vehicles need to come to a complete stop due to pedestrians or cross-traffic.
Rectangle (Taller) and Square – These types of signs provide regulatory information such as pedestrian crossings, “No Turn on Red,” and “Speed Limit 50,” to name just a few. Each of these signs corresponds to a specific city traffic law.
Rectangle (Shorter) and Square – This category consists of a guide, several traffic control, and a few warning signs. You can find them in various places in the city, highway, and countryside. There are also a few signs that convey regulatory/warning information, such as “Traffic Laws Photo Enforced.”
Pennant – Many people often wonder what pennant-shaped signs indicate. They’re exclusively used for a “No Passing Zone” and are usually found in construction zones and other areas where conditions will not allow for the safe passing of other motor vehicles.
Crossbuck – A crossbuck sign is exclusively used to warn motorists and pedestrians of a railroad crossing. They’re placed within a very short distance of the railroad tracks.
Trapezoid – Trapezoid shaped signs are found in national forests, recreational, and places of cultural interest. They can also indicate route markers in rural areas.
Shield – A sign in the shape of a shield often denotes a highway or interstate route number. The number of the sign is the largest element which provides essential information to the motorist.
Road Sign Design and Manufacturing
Standardized road sign shapes enable motorists to quickly understand and safely react to the information, regardless of placement or visibility concerns. However, their shape is only one part of the safety equation.
Click the button below to learn more about the important role road sign colors play in keeping both drivers and pedestrians safe.