Traffic Signals and Traffic Signs on Roadways within Charles County

By: Harry F. Price, Engineer II

      Capital Services - Transportation Division

The most common and widely used device for controlling traffic on high volume roadways is the traffic control signal (traffic signal). In 1914, the first electrically-operated traffic signal was introduced in Cleveland, Ohio. Having both audio and visual components, the traffic signal was equipped with two (2) long cross arms, red and green lights and buzzers. It was originally designed and constructed to alleviate out-of-control traffic conditions and major traffic congestion. Since then, the evolution of the traffic signal has had major design improvements and has played an integral role in our everyday lives.

The Traffic Signal

Prior to installing any new traffic signals and/or pedestrian amenities in Charles County, a professional engineer must submit a "Design Request" application to the Maryland State Highway Administration for design consideration and commitment. An in-depth traffic engineering study which has undergone extensive planning must meet all compliance review requirements. Final approval is either granted or denied by MSHA's Office of Traffic and Safety. A cost share agreement between MSHA and Charles County must also be agreed upon by both parties and an initial inspection fee must be paid. The cost share agreement also covers all MSHA future maintenance and repair costs for the new traffic signal.

All new studies for installation of traffic signals are based upon the following criteria documented in the national "Manual on Uniform Traffic Control Devices":

• consistently high traffic volume
• an accident rate which may be reduced
• excessive wait time for vehicles or pedestrians to cross an intersection
• restricted visibility
• a high volume of pedestrian traffic

Figure 1: Typical traffic control signal in Charles County with pedestrian amenities.

All new traffic signals in Charles County play an integral role in ensuring equal and safe traffic coordination for both the motorist and the pedestrian. Our traffic signal designs incorporate the latest technology developed for enhanced operations by providing video detection cameras, light emitting diode (LED) signal displays, NEMA electrical equipment and battery backup systems, audible pedestrian push button countdown systems with pedestal poles, steel mast arm traffic signal poles, and hazard identification signs for the control signal equipment to maintain pedestrian safety and compliance. Our intersections include Federal ADA-compliant sidewalk ramps with detectable warning surfaces, and reflective white colored pedestrian crosswalk designs. The definition and purpose of the traffic signal has not changed much over the years except that pedestrians are more recognized these days, and are better protected at crossings by including electronically voice activated push-button pedestrian crossing equipment and intersection lighting.

Figure 2: Traffic signal construction underway at St. Patrick's Drive, in Waldorf.

 Motorists and pedestrians, especially those residing in the more populated communities of Waldorf, are aware that traffic signals are sophisticated signalizing devices which are mostly equipped with circular red, yellow and green lights. Other shapes and applications sometimes include a red, yellow and green arrow, and/or a flashing yellow light. Whatever the case may be, the new traffic signals, digital lights, and pedestrian crossings have helped reduce the traffic congestion in the Waldorf community.

Traffic Signs

Regulatory signs in Charles County also play an important role to the motorists as they are used to convey important and prompt messages to the roadway users. Symbols for stopping, warning against making illegal left turns, traffic signal ahead and simply traveling the posted speed limit are good examples of providing instant communication with the typical roadway user. The symbol alone can sometimes help overcome language barriers and are quickly becoming a standard for traffic control devices throughout the United States. You may also have noticed recently that the Federal and State Highway Administration has added many new sign shapes and symbols, and have eliminated wording that once existed on older signs in our area.

The use of red on signs in Charles County is limited to stop, yield and prohibition signs. A white background indicates a regulatory sign, yellow conveys a general warning message, green shows permitted traffic movements or directional guidance, fluorescent yellow or green indicates pedestrian crossings at school zones, an orange background is used for warning guidance in roadway work zones, blue indicates road user services, tourist information and evacuation routes, while a brown background is used for guidance to public recreation or a cultural interest site.

In addition, the shape of the sign especially in Charles County can alert the motorist and pedestrian user to the type of information being displayed. Traffic regulations are conveyed in many signs that are rectangular in shape with the longer direction vertical or square. Other regulatory signs are octagons for stop and inverted triangles for yield. Diamond-shape signs signify warnings, while rectangular and longer direction horizontal signs provide guidance information. A circular sign warns the motorist of an upcoming railroad crossing.

Figure 3: Typical signs posted in construction work zones and no crossing area.

In summary, the purpose of a regulatory sign is to inform the roadway user or motorists of traffic laws and regulations and to indicate the applicability of legal requirements that would not otherwise be apparent. Motorists, bicyclists, and pedestrians should always be directed in the safest path as possible whether it is at a traffic signal or along a particular roadway. As good highway design engineers and project managers in Charles County, we are committed to designing and building roads to ensure that the highest safety standards and quality control are always being met and are never compromised.