Section 3: Lane Geometry and Arrow Orientation

Introduction

This section covers guide sign arrow orientation based on route direction and various freeway lane geometries. The guidance in this section is primarily for freeway-to-freeway interchanges, which are discussed in the next section; however, the guidance may be used for other types of interchanges if additional lane assignment is necessary.

Route Arrangement and Lane Geometry

Figure 5‑8 illustrates the three basic types of route arrangements that can exist at a freeway-to-freeway interchange. These include:

The freeway continues to the left and traffic exits to the right to a different freeway. This arrangement is most consistent with driver expectancy.

The freeway continues to the right and traffic exits to the left to a different freeway. This is a left exit condition.

The freeway ends at another freeway. Traffic exits the ending freeway to travel in either direction on the other freeway.

For each route arrangement, three types of lane geometries are possible. These include:

The left branch is on a tangent alignment, and the right branch is curved.

Both the left and right branches are on a curved alignment.

The right branch is on a tangent alignment, and the left branch is curved.

Figure 5‑8 illustrates nine combinations of route arrangements that are possible when an optional lane serves both the continuing and exiting routes. Similar combinations are possible when no optional lane is present.

Figure 5-8. Route direction and lane geometry at an interchange.

Arrow Orientation

When lane assignment is desired, all exiting lanes at that location should be marked with down arrows and/or upward slanting arrows on overhead Advance Guide and Exit Direction signs.

Advance Guide signs, either with or without Exit Only panels, are located upstream of the gore and should have only one downward arrow per travel lane. In some cases, two destinations can be reached from one lane (an optional lane), and only one downward arrow should be placed for that lane on the Advance Guide signs. This arrow should be placed on the through Interstate Highway route. If the route ends at the split, or if both destinations are non-Interstate Highway routes, the downward arrow on the Advance Guide signs for the optional lane should be placed for the destination with the higher traffic volume or the route that favors a through movement.

Exit Direction signs, either with or without Exit Only panels, are located at the gore location and may have downward and/or upward slanting arrows depending on the lane geometry of the freeway lanes. The following general rules apply to the use of arrows on Exit Direction signs for freeway-to-freeway interchanges:

If a Pull-Through sign is used at the gore for the continuing route, the type of arrow is determined as follows:


If the continuing route is…	Then…
on a tangent alignment in the vicinity of the gore	down arrows are used.
not on tangent alignment in the vicinity of the gore	upward slanting arrows are used.

Upward slanting arrows are used for the exiting route.

Upward slanting arrows are used for both directions when a route ends at another freeway.

The number of arrows on the sign structure must be equal to the number of lanes underneath the sign structure, unless there is an optional lane. When there is an optional lane, the number of arrows on the sign structure may be the same as the number of lanes immediately downstream of the structure, if the structure is located within the lane-increase transition.

Pull-Through Signs

Although shown in the illustrations in this section, Pull-Through signs may not be necessary at all freeway-to-freeway interchanges.

Arrow Placement for Route Continuing to the Left

The following table illustrates Advance Guide and Exit Direction sign arrow orientation when the freeway route continues to the left. The examples are based on three approach lanes, but additional lanes may be present on the right or left sides.

Advance Guide and Exit Direction Sign Arrow Orientation for Route Continuing Left
Lane Geometry	Sign Type	Left Route Signing
	Exit Direction Sign	Sign and/or Arrows Not Necessary¹
	Advance Guide Signs	Sign and/or Arrows Not Necessary¹
	Exit Direction Sign
	Advance Guide Signs
	Exit Direction Sign
	Advance Guide Signs
	Exit Direction Sign	Sign and/or Arrows Not Necessary¹
	Advance Guide Signs	Sign and/or Arrows Not Necessary¹
	Exit Direction Sign
	Advance Guide Signs²
	Exit Direction Sign
	Advance Guide Signs²
¹Typical right-lane exit where arrows are not necessary for the through route.
²Two arrows on the Advance Guide signs favor the through Interstate Highway. If the route ends at the split, or if both destinations are non-Interstate Highway routes, the downward arrow on the Advance Guide signs for the optional lane should be placed for the destination with heaviest traffic volume movement (see Figure 5‑8).

Arrow Placement for Route Continuing to the Right

The following table illustrates Advance Guide and Exit Direction sign arrow orientation when the freeway route continues to the right. The examples are based on three approach lanes, but additional lanes may be present on the right or left sides.

Advance Guide and Exit Direction Sign Arrow Orientation for Route Continuing Right
Lane Geometry	Sign Type	Right Route Signing
	Exit Direction Sign
	Advance Guide Signs
	Exit Direction Sign
	Advance Guide Signs
	Exit Direction Sign	Sign and/or Arrows Not Necessary
	Advance Guide Signs	Sign and/or Arrows Not Necessary¹
	Exit Direction Sign
	Advance Guide Signs²
	Exit Direction Sign
	Advance Guide Signs²
	Exit Direction Sign	Sign and/or Arrows Not Necessary¹
	Advance Guide Signs	Sign and/or Arrows Not Necessary¹
¹Typical left-lane exit where arrows are not necessary for the through route.
²Two arrows on the Advance Guide signs favor the through Interstate Highway. If the route ends at the split, or if both destinations are non-Interstate Highway routes, the downward arrow on the Advance Guide signs for the optional lane should be placed for the destination with heaviest traffic volume movement (see Figure 5‑8).

Arrow Placement for Route Ending

The following table illustrates Advance Guide and Exit Direction sign arrow orientation for when the freeway route ends and exits to another freeway. The examples are based on three approach lanes, but additional lanes may be present on the right or left sides.

Advance Guide and Exit Direction Sign Arrow Orientation for Route Ending
Lane Geometry	Sign Type	Left Route Signing	Right Route Signing
	Exit Direction Sign
	Advance Guide Signs
	Exit Direction Sign
	Advance Guide Signs
	Exit Direction Sign
	Advance Guide Signs
	Exit Direction Sign
	Advance Guide Signs1
	Exit Direction Sign
	Advance Guide Signs¹
	Exit Direction Sign
	Advance Guide Signs¹
¹Two arrows on the Advance Guide signs favor the through Interstate Highway. If the route ends at the split, or if both destinations are non-Interstate Highway routes, the downward arrow on the Advance Guide signs for the optional lane should be placed for the destination with heaviest traffic volume movement (see Figure 5‑8).