TRAFFIC CONTROL DEVICES

Regulatory Signs

Regulatory signs inform highway users of traffic laws or regulations. These signs are rectangular with a black legend on white background. Other colors and shapes are also used. The two most common regulatory signs indicate right- of-way. These are the stop sign and yield sign.

Regulatory signs are used to control speeds, such as maximum and minimum speed limits. They are also used to control turning movement. As an example, you may recognize these signs with a red circle and a slash mark, which means, “no” or “do not.”

Regulatory signs control parking. When parking is prohibited, the parking signs have red lettering, such as “No Parking at Any Time,” “No Stopping Standing or Parking,” or “No Parking, Bus Stop.” When parking is permitted, the lettering is green, such as “One Hour Parking.”

Regulatory signs can also be used to supplement information given by traffic signals, such as “Stop Here on Red” or “Crosswalk.” Finally, regulatory signs are used for a variety of other controls, such as to provide axle weight limit (GVWR) or “Road Closed to Through Traffic.”

Warning Signs

Warning signs inform the driver of situations ahead that may require extra care. These signs are yellow with black lettering and generally are diamond shaped. Warning signs can be used to show changes in horizontal alignment, such as turns, curves, and winding roads. Various types of intersections ahead are indicated symbolically. These signs can indicate crossroads or “T” and “Y” intersections. Advance warning of traffic control devices can be provided.

Sometimes a written message is used, such as “Stop Ahead,” or a picture of the device ahead is used, such as a yield sign or traffic signal.

Warning signs are used to show converging traffic lanes, such as the symbolic merge sign or the message or symbolic sign for showing that the right lane ends. They are also used to indicate narrow roadways, such as “Road Narrows” or “One Lane Bridge.” Changes in highway design are shown on warning signs as well. Examples include divided highway ahead, divided highway ends, or two-way traffic.

Traffic engineers are increasing the use of roundabouts. Drivers must use particular attention to both warning signs and pavement indicators in these areas. If the driver becomes confused in these areas, the driver must not stop in the roundabout. The driver should proceed to a connecting road tore-route.

Highway grades and advance warning of railroad crossings are indicated on warning signs. Roadway surface conditions, such as bumps, soft shoulders, and slippery conditions, are also indicated. Various kinds of entrances and crossings are shown on warning signs, such as truck entrance, deer crossing, and bicycle crossing.

Warning signs are used to indicate advisory speeds, such as exit and ramp speeds.

A special type of warning sign is the pennant shaped “No Passing Zone” sign. When used, it is on the left side of the road and is used in conjunction with the regulatory “Do Not Pass” sign.

Finally, school signs are special kinds of warning signs utilizing the pentagon shape. These indicate school area and school crossing.

Guide Signs

Guide signs are the third major classification of traffic signs. Guide signs guide drivers along streets and highways, inform them of intersecting routes, or direct them to their destination, be it a city, river, park, or some similar type of destination. Guide signs are generally rectangular and have a white message on a green background. On conventional roads and streets, black messages on white backgrounds are frequently used as an alternative. In addition, different colors and shapes are used for special purposes.

Guide signs are used to indicate junctions of highways, the direction of a highway, alternate routes, the end of a numbered route, and temporary routes. A variety of advance route turn arrows and directional arrows are common guide signs. Two of the most typical guide signs are the familiar destination and mileage signs. On some of the interchanges, symbolic destination signs are used. A special type of guide sign is used for recreation areas. These signs have a white message on a brown background.

Another special guide sign is the service sign. These are white messages on a blue background. These illustrate the location of a phone or hospital. They also indicate that there are no barriers to the handicapped.

Other service signs indicate gas, food, lodging, or camping either through symbolic or message signs. Mileposts are another form of guide sign. Mileage always runs from south to north or west to east and begins at the state line or at a junction where the route begins. Guide signs are also used to show the locations of airports, bus stations, and train stations.

Finally, special panels reading, “Exit Only,” advise drivers of an imminent lane end situation. These signs use the warning sign combination of black letters on a yellow background. Highway construction and maintenance signs fall into the same three major classifications as other signs, namely regulatory, warning, and guide signs. Regulatory signs used in construction and maintenance zones use the normal standard colors, shapes, and messages.

Warning guide signs also use the standardized shapes and messages but are distinctive in the black letters used on an orange background. Typical construction and maintenance warning signs warn of construction or a detour ahead. They can also warn of roadwork, shoulder work, or a survey crew ahead. Typical construction and maintenance guide signs provide information on the length of a construction or maintenance zone or the direction of a detour.

 Electronic Traffic Signals

These are valuable devices to control traffic and assign right-of- way. The message in traffic signals is relayed primarily using colors; therefore, the meaning of the colors has been standardized.

Ø  A steady circular green signal permits traffic to proceed if it is safe to do so.

Ø  A steady circular yellow signal always follows a circular green signal or green arrow and warns that the red signal is about to be shown. Drivers must stop if it is possible, and safe to do so.

Ø  A steady circular red signal means to stop, and remain stopped until a green signal is shown, and it is safe to proceed.

Ø  A steady green arrow may be used instead of a steady circular green signal. The driver is permitted to proceed in the direction(s) of the arrow(s) if it is safe to do so.

Ø  A flashing circular red signal means stop and remain stopped until it is safe to proceed. Flashing red signals are used at particularly dangerous locations.

Ø  A flashing circular yellow signal is a warning of a hazardous location. Drivers may proceed through but should use extreme caution.

Road Markings

Like traffic signs and signals, roadway markings have a definite purpose and convey a special meaning. In some cases, they supplement the regulations and warnings conveyed on traffic signs and signals. In other instances, they are used alone as there is no other way to effectively communicate this information. Roadway markings are standardized as to color and type of line.

Ø  White lines delineate separation of traffic flows in the same direction.

Ø  Yellow lines delineate separation of traffic flows in the opposite direction.

Ø  Broken lines are permissive in nature. When traffic permits, broken lines may be crossed.

Ø  Solid lines are restrictive in nature. Generally, they are not to be crossed.

Ø  Double solid lines indicate maximum restriction. They are not to be crossed.

Ø  Broken white lines separate traffic lanes moving in the same direction when the roadway has more than one lane of traffic moving in the same direction. Drivers are to drive between the lines and not straddle the lines. When traffic permits, broken white lines may be crossed to change lanes.

Ø  A solid white line is used to mark the edge of the roadway/pavement.

Ø  Pavement edge lines should not be crossed at moderate to high speeds. They may be crossed, however, at slow speeds when it is necessary to pull off onto the shoulder. When solid white lines separate lanes of traffic moving in the same direction, it is recommended to not cross lanes.

Ø  Broken yellow lines separate traffic moving in the opposite direction. When the broken yellow line is on the driver’s side of the road, it may be crossed if oncoming traffic permits.

Ø  Solid yellow lines also separate traffic moving in the opposite direction. When the solid yellow line is on the driver’s side of the road, it must not be crossed.

Ø  A solid and broken yellow line used together is to delineate a left turn lane. The left turn lane is marked on both sides by both a solid and broken yellow line. Drivers turning left must turn from this lane.

Ø  A double solid yellow line is used to indicate that traffic from both directions is prohibited from crossing.