Perennial Service. This uses traffic lights to reinforce STOP and YIELD signs. In fact, MUTCD 4K.2 requires a STOP sign to augment a flashing red dot when in perennial service. Analogously, TFGAP recommends the YIELD sign be posted at any perennial flashing green signal. Yellow or steady red lights will never need signs, because they are not displayed in perennial service.

In some cases the signals are attached directly to the signs (dots; arrows).

The following tables present some examples of TFGAP traffic lights that might be used in perennial service. Anything that works in perennial service can also be used as a long-term state in ephemeral service. The reader should note that each table does not present a phasing sequence; rather, each row is a separate configuration.

Table 4A1 shows some likely combinations at a four-leg intersection.

Table 4A1 -- Vine and Elm
Vine Street	Elm Street	Comments
		All-way stop.
		Two-way stop favoring Vine.
		Two-way stop favoring Elm.
		Two-way yield favoring Vine.
		Two-way yield favoring Elm.

Table 4A2 points out two faulty combinations.

Table 4A2 -- Vine and Elm
Vine Street	Elm Street	Comments
		All-way stop, as above. Recommended.
		All-way yield. NOT recommended.
		Some-way stop, some-way yield. NOT recommended.

Under the lights of table 4A2, all motorists are expected to yield. There will often be a case where two approaching drivers ostensibly must yield to each other, and something has to be done to "break the tie". Important to remember is that motorists on one approach often cannot see the signals presented to other approaches, although section 5 addresses this problem in part.

• Drivers who approach an all-way stop, and who happen to be aware of the configuration, will observe the traditional criteria for behavior at the intersection. In particular, the rule of "first to stop, first to go" settles most cases. If on the other hand the approaching driver does not happen to know what kind of signal cross traffic sees, she still must stop. Then she will have an opportunity to assess the motion of other vehicles and decide what to do.
• It is not clear how the all-way yield might differ from a completely uncontrolled intersection. Most highway departments regard this as extremely unsafe, as evidenced by its rarity. The resolution criterion often invoked is that a driver must yield to another driver on her right. Illustrating the characteristic problem is a case where two motorists are moving toward an intersection; they are at different distances from the crossroad, and are traveling at different speeds. There is a good chance that they will consequently have different judgements about whether the driver on the left can safely clear the intersection before the driver on the right reaches it. High-speed right-angle crashes become a risk.
• The some-way stop, some-way yield raises questions about whether the motorists with green might have some kind of precedence over the motorists with red, since green customarily gives drivers more freedom than red. Moreover, the driver with the FGD, who is not generally required to stop, might be puzzled by her obligation to yield to a motorist on the crossroad who has stopped and appears to be waiting for her.

• Flashing red for all,
• Flashing red versus steady green,
• Flashing green versus steady green.

Table 4A3 lists some combinations at a three-leg intersection, and introduces arrows.

Table 4A3 -- Vine and Maple
Vine Street	Maple Street	Comments
		All-way stop, this time a three-way.
		One-way stop favoring Maple.
		As above, with emphasis to Vine that going straight is wrong.
		One-way yield favoring Maple.
		As above, with emphasis to Vine that going straight is wrong.
		Two-way stop favoring Vine; unusual at a tee intersection.

None of these shows a steady green turn arrow, because that signal implies a protected movement and we have presumed that at all intersections pedestrians will be permitted to cross. However, a steady green straight-through arrow will sometimes be suitable.

Turn arrows can also be valuable when trying to prevent wrong-way turns onto one-way streets.

We suggest that in general opposing directions of traffic see exactly the same configurations of dots and arrows. However, an exception may be justified when opposing approaches are channelized differently, and all drivers have a good view of the situation. Suppose that at the Vine Street intersection, northbound Elm Street has a dedicated right-turn lane with prominent traffic island, and southbound Elm Street has no special treatment.

Table 4A4 -- Vine and Elm, with Channelized Turn
Vine Street	Elm Street			Comments
	northbound		southbound
	left and straight	right
				All-way stop.
				Two-way stop favoring Elm.
				Two-way yield favoring Elm.
				Two-way stop favoring Vine.
				Same as previous, except northbound Elm's right turn need not stop.
				Two-way yield favoring Vine.
				Same as previous, except northbound Elm's right turn must stop. This is suitable when the turn involves unusual dangers.

In only two of the examples of table 4A4 are northbound Elm's signals of different colors; in them, the arrow has genuine control value. In the five other examples the arrow serves merely to remind the drivers in the right-turn lane of their obligation to make that move.