Chapter 7 - At Grade Intersections

7.5. Signalization

The designer should be familiar with the current version of the GDOT TOPPS 6785-1, Traffic Signals. The information contained in this Section is intended to supplement the information contained in TOPPS 6785-1. The following provides some general guidelines for signalized intersection design:

• All signalized intersections shall be designed in accordance with the GDOT Traffic Signal Design Guidelines

• Distance between stop bars on opposing movements should be set to minimum standards wherever possible, thus minimizing necessary clearance timings.

• The use of pedestrian refuge islands should be considered whenever possible to minimize pedestrian clearance times.

• The designer should communicate with the District Utilities Engineer to compile a list of all utilities which may be affected both underground and overhead. The location of utilities should be included on the signal plans so that they may be avoided. Special attention should be given to overhead utilities crossing the intersection to ensure that they do not conflict with the proposed signal span wire, mast arms, or signal heads, and that the design is able to meet National Electric Safety Code requirements.

• Actual (existing) and projected (design) volumes, including turn movements, should be collected and determined for the intersection.

• The designer should determine if the proposed signal will be part of a coordinated signal system, and if so, the development of communication plans or timing plans are needed.

• The designer should closely evaluate the sequence of construction and maintenance of traffic to determine if temporary signals are needed.

• Where possible signal poles / mast arms should be located to allow for use with both temporary signalization, and final signalization.

• The intersection controller cabinet shall be located where it can be utilized in the temporary signals, as well as the final signal design. 

• Location of the PED button and PED signal, curb cut ramps, strain pole, controller cabinets, crosswalk and landing areas, should all be coordinated to ensure a fully accessible intersection.  The designer should check the right of way to ensure that there is enough room to install these items. 

• The intersection controller cabinet shall be located to avoid creating a sight distance obstruction in all phases of construction.

• Signal heads shall be designed with sufficient slack wiring to allow the heads to be relocated to different places on the span wire / mast arm for use in both the temporary and final signals.

• Wherever possible, loops, pullboxes, and loop lead-ins shall be placed to be used for both the temporary signals as well as the final signals.

• For signals mounted on mast arms, the designer should provide sufficient length on the arms to allow for both future signal heads, as well as field adjustments if needed.

 

• The designer should contact the maintaining agency that is responsible for the existing intersections in the area to determine design standards which may be unique to the area.

• As applicable, the construction of the signalized intersection should be carefully considered when developing maintenance of traffic plans.

• Consider decision sight distance as it relates to signal head and traffic control devices, and the queue length for the signal.

• When designing a roadway or roadway improvements, particular attention should be paid to the future operations at the project intersections. Where existing signalization does not exist, the intersection should be evaluated to determine if signalization is required as part of the project. If the project includes an existing signalized intersection, the intersection should be evaluated to determine if improvements are required as part of the project.