Modes of Operation

Left-turning traffic is controlled by one of four modes as follows: protected only, protected permissive, permissive only, or variable by time of day.
  • Permissive-Only Mode.
     Turns are allowed on a CIRCULAR GREEN signal indication, a flashing left-turn YELLOW ARROW signal indication, or a flashing left-turn RED ARROW signal indication after yielding to pedestrians, if any, and/or opposing traffic, if any. If a separate signal section is provided for the left-turn lane, the signal face will need to be as shown in TMUTCD Figure 4D-7 and will require modification to the controller cabinet to provide the Flashing Yellow Arrow (FYA) operation. Alternatively, the approach can be provided with signal faces as illustrated in TMUTCD Figure 4D-6, without need for cabinet modification.
  • Protected-Only Mode.
     Turns are allowed only when a left-turn GREEN ARROW signal indication is displayed. Signal indications for protected-only mode left turns in a separate signal face are required to be 3-section signal faces with RED ARROW, YELLOW ARROW, GREEN ARROW indications. Signal indications for protected-only mode in a shared signal face are required to be Circular RED, YELLOW, GREEN, GREEN ARROW indications. This would be for use where the circular GREEN and GREEN ARROW indications always begin and end together (i.e. Split phasing).
  • Protected-Permissive Mode.
     Both protected and permissive modes can occur on an approach during the same cycle. Signal indications for protected-permissive mode in a separate left-turn signal face are required to be RED ARROW, YELLOW ARROW, Flashing YELLOW ARROW, and GREEN ARROW (a flashing RED ARROW is also allowed). Signal indications for protected-permissive mode in a shared signal face are required to be Circular RED, YELLOW, GREEN, YELLOW ARROW and GREEN ARROW. Initially, TxDOT practice for protected-permissive left-turn mode for standard diamond interchanges was to use a shared signal face. This is no longer the case, separate signal faces with flashing yellow arrow displays may be used for standard diamond interchanges.
  • Variable Left-Turn Mode.
     The operating mode changes among the protected-only mode and/or the protected-permissive mode and/or the permissive-only mode during different periods of the day or as traffic conditions change. Variable mode operation requires signal indications as defined above for a separate protected-permissive signal face. Variable mode may be implemented by time of day or possibly by rail or emergency preemption.