Multi-Lane control system

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Lane control signals for countries driving on the right. Flashing red is sometimes used instead of yellow. Lane control with speed limits used instead of arrows

Lane control lights are a specific type of traffic light used to manage traffic on a multi-way road or highway. Typically they allow or forbid traffic to use one or more of the available lanes by the use of Green lights or arrows (to permit) or by red lights or crosses (to prohibit). When used, they are usually repeated at regular distances to provide a continuous reminder of the lane status to drivers.

On certain multiple-lane highways, one or more lanes may be designated as counterflow lanes, meaning that the direction of traffic in those lanes can be reversed at any time (see also reversible lane). Sometimes this is done as a way of managing rush hour traffic (one or more central lanes may flow inbound in the morning and outbound in the evening); in other cases the lanes are reversed only in unusual circumstances (such as a traffic accident or road construction closing one or more of the lanes).

Signal conventions

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Lane control signals around the world follow their own universal pattern, as specified in the Vienna Convention on Road Signs and Signals.[1]: Art.23, ¶11  Typical signals include a green downward arrow, used to indicate a lane which is open to traffic facing the signal, a red cross, which indicates a lane is either reserved for opposing traffic or closed to traffic in both directions, and a flashing amber circle, arrow or cross, indicating to traffic facing the signal to immediately clear the lane.

This parking ramp uses lane control signals so that the middle lane's direction may be changed according to time of day.

Unlike regular traffic lights, lane control signals either have one face each to indicate all lane conditions (the so-called "searchlight" configuration), or separate faces for each condition (as illustrated). Lane control signals of the latter type are usually placed horizontally. Signals that may indicate other conditions for roads without counterflow lanes also exist, such as those that indicate different speed limits for different lanes.

Examples

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Lane control signals installed on the Old Champlain Bridge in Montréal, Canada

In the Australian state of Victoria, green and yellow are replaced by white, and there may be additional modes such as 'Centre lane turns only' at particular times of the day.

On Jarvis Street in Toronto, Edmonton and some other jurisdictions in Canada the lane control signals are employed without the use of an amber warning signal. Instead, the lane that is to undergo the direction reversal (the middle lane of a five-lane downtown street) is marked with a red cross in both directions for a short period of time. This allows time for the lane to clear of traffic before a green arrow permits traffic in the reversed direction. However, Jarvis Street was converted to a four-lane arterial with bicycle lanes in 2009, and was converted back to a five-lane road in 2012.

In Greece, they are frequently used in tunnels to indicate lane closures because of accidents or roadworks.

Toll plazas in the United States

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In the United States, lane control signals are used on many toll plazas to indicate the open/closed status of toll lanes. Many older toll plazas use conventional circular red and green indications to indicate the open and closed status of toll lanes; however, the use of circular red and green signals for this purpose is now non-compliant in the 2009 Manual on Uniform Traffic Control Devices, with lane control signals being the preferred indicator.[2] The reason for discouraging the use of circular red and green signals for indicating the open and closed status of toll lanes is due to their use being contrary to their traditional definitions of stop and go.

References

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Back to 2003 Edition with Revisions Number 1 and 2 Incorporated  |  Back to Part 4 Table of Contents

Chapter 4J. Lane-Use Control Signals

Section 4J.01

Application of Lane-Use Control Signals

Support:
Lane-use control signals are special overhead signals that permit or prohibit the use of specific lanes of a street or highway or that indicate the impending prohibition of their use. Lane-use control signals are distinguished by placement of special signal faces over a certain lane or lanes of the roadway and by their distinctive shapes and symbols. Supplementary signs are sometimes used to explain their meaning and intent.

Lane-use control signals are most commonly used for reversible-lane control, but are also used in nonreversible freeway lane applications.

Guidance:
An engineering study should be conducted to determine whether a reversible-lane operation can be controlled satisfactorily by static signs (see Section 2B.25) or whether lane-use control signals are necessary. Lane-use control signals should be used to control reversible-lane operations if any of the following conditions are present:

1. More than one lane is reversed in direction;
2. Two-way or one-way left turns are allowed during peak-period reversible operations, but those turns are from a different lane than used during off-peak periods;
3. Other unusual or complex operations are included in the reversible-lane pattern;
4. Demonstrated crash experience occurring with reversible-lane operation controlled by static signs that can be corrected by using lane-use control signals at the times of transition between peak and off-peak patterns; and/or
5. An engineering study indicates that safer and more efficient operation of a reversible-lane system would be provided by lane-use control signals.

Option:
Lane-use control signals also may be used for reversible-lane operations at toll booths. They may also be used if there is no intent or need to reverse lanes, including:

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1. On a freeway, if it is desired to keep traffic out of certain lanes at certain hours to facilitate the merging of traffic from a ramp or other freeway;
2. On a freeway, near its terminus, to indicate a lane that ends; and
3. On a freeway or long bridge, to indicate that a lane may be temporarily blocked by a crash, breakdown, construction or maintenance activities, and so forth.

Section 4J.02

Meaning of Lane-Use Control Signal Indications

Standard: The meanings of lane-use control signal indications are as follows:

1. A steady DOWNWARD GREEN ARROW signal indication shall mean that a road user is permitted to drive in the lane over which the arrow signal indication is located.
2. A steady YELLOW X signal indication shall mean that a road user is to prepare to vacate, in a reasonably safe manner, the lane over which the signal indication is located because a lane control change is being made to a steady RED X signal indication.
3. A steady WHITE TWO-WAY LEFT-TURN ARROW signal indication (see Figure 4J-1) shall mean that a road user is permitted to use a lane over which the signal indication is located for a left turn, but not for through travel, with the understanding that common use of the lane by oncoming road users for left turns is also permitted.
4. A steady WHITE ONE WAY LEFT-TURN ARROW signal indication (see Figure 4J-1) shall mean that a road user is permitted to use a lane over which the signal indication is located for a left turn (without opposing turns in the same lane), but not for through travel.
5. A steady RED X signal indication shall mean that a road user is not permitted to use the lane over which the signal indication is located and that this signal indication shall modify accordingly the meaning of all other traffic controls present. The road user shall obey all other traffic controls and follow normal safe driving practices.

Pavement markings (see Section 3B.03) shall be used in conjunction with reversible-lane control signals.

Figure 4J-1 Left-Turn Lane-Use Control Signals

Section 4J.03

Design of Lane-Use Control Signals

Standard:
All lane-use control signal indications shall be in units with rectangular signal faces and shall have opaque backgrounds. Nominal minimum height and width of each DOWNWARD GREEN ARROW, YELLOW X, and RED X signal face shall be 450 mm (18 in) for typical applications. The WHITE TWO-WAY LEFT-TURN ARROW and WHITE ONE WAY LEFT-TURN ARROW signal faces shall have a nominal minimum height and width of 750 mm (30 in).

Each lane to be reversed or closed shall have signal faces with a DOWNWARD GREEN ARROW and a RED X symbol.

Each reversible lane that also operates as a two-way or one-way left-turn lane during certain periods shall have signal faces that also include the applicable WHITE TWO-WAY LEFT-TURN ARROW or WHITE ONE WAY LEFT-TURN ARROW symbol.

Each nonreversible lane immediately adjacent to a reversible lane shall have signal indications that display a DOWNWARD GREEN ARROW to traffic traveling in the permitted direction and a RED X to traffic traveling in the opposite direction.

If in separate signal sections, the relative positions, from left to right, of the signal indications shall be RED X, YELLOW X, DOWNWARD GREEN ARROW, WHITE TWO-WAY LEFT-TURN ARROW, WHITE ONE WAY LEFT-TURN ARROW.

The color of lane-use control signal indications shall be clearly visible for 700 m (2,300 ft) at all times under normal atmospheric conditions, unless otherwise physically obstructed.

Lane-use control signal faces shall be located approximately over the center of the lane controlled.

If the area to be controlled is more than 700 m (2,300 ft) in length, or if the vertical or horizontal alignment is curved, intermediate lane-use control signal faces shall be located over each controlled lane at frequent intervals. This location shall be such that road users will at all times be able to see at least one signal indication and preferably two along the roadway, and will have a definite indication of the lanes specifically reserved for their use.

All lane-use control signal faces shall be located in a straight line across the roadway approximately at right angles to the roadway alignment.

The bottom of the signal housing of any lane-use control signal face shall be at least 4.6 m (15 ft) but not more than 5.8 m (19 ft) above the pavement grade.

On roadways having intersections controlled by traffic control signals, the lane-use control signal face shall be located sufficiently far in advance of or beyond such traffic control signals to prevent them from being misconstrued as traffic control signals.

Option:
In areas with minimal visual clutter and with speeds of less than 70 km/h or less than 40 mph, lane-use control signal faces with nominal height and width of 300 mm (12 in) may be used for the DOWNWARD GREEN ARROW, YELLOW X, and RED X signal faces, and lane-use control signal faces with nominal height and width of 450 mm (18 in) may be used for the WHITE TWO-WAY LEFT-TURN ARROW and WHITE ONE-WAY LEFT-TURN ARROW signal faces.

Other sizes of lane-use control signal faces larger than 450 mm (18 in) with message recognition distances appropriate to signal spacing may be used for the DOWNWARD GREEN ARROW, YELLOW X, and RED X signal faces.

Nonreversible lanes not immediately adjacent to a reversible lane on any street so controlled may also be provided with signal indications that display a DOWNWARD GREEN ARROW to traffic traveling in the permitted direction and a RED X to traffic traveling in the opposite direction.

The signal indications provided for each lane may be in separate signal sections or may be superimposed in the same signal section.

Section 4J.04

Operation of Lane-Use Control Signals

Standard:
All lane-use control signals shall be coordinated so that all the signal indications along the controlled section of roadway are operated uniformly and consistently. The lane-use control signal system shall be designed to reliably guard against showing any prohibited combination of signal indications to any traffic at any point in the controlled lanes.

For reversible-lane control signals, the following combination of signal indications shall not be shown simultaneously over the same lane to both directions of travel:

1. DOWNWARD GREEN ARROW in both directions;
2. YELLOW X in both directions;
3. WHITE ONE WAY LEFT-TURN ARROW in both directions;
4. DOWNWARD GREEN ARROW in one direction and YELLOW X in the other direction;
5. WHITE TWO-WAY LEFT-TURN ARROW or WHITE ONE WAY LEFT-TURN ARROW in one direction and DOWNWARD GREEN ARROW in the other direction;
6. WHITE TWO-WAY LEFT-TURN ARROW in one direction and WHITE ONE WAY LEFT-TURN ARROW in the other direction; and
7. WHITE ONE WAY LEFT-TURN ARROW in one direction and YELLOW X in the other direction.

A moving condition in one direction shall be terminated either by the immediate display of a RED X signal indication or by a YELLOW X signal indication followed by a RED X signal indication. In either case, the duration of the RED X signal indication shall be sufficient to allow clearance of the lane before any moving condition is allowed in the opposing direction.

Whenever a DOWNWARD GREEN ARROW signal indication is changed to a WHITE TWO-WAY LEFT-TURN ARROW signal indication, the RED X signal indication shall continue to be displayed to the opposite direction of travel for an appropriate duration to allow traffic time to vacate the lane being converted to a two-way left-turn lane.

If an automatic control system is used, a manual control to override the automatic control shall be provided.

Guidance:
The type of control provided for reversible-lane operation should be such as to permit either automatic or manual operation of the lane-use control signals.

Standard:
If used, lane-use control signals shall be operated continuously, except that lane-use control signals that are used only for special events or other infrequent occurrences and lane-use control signals on nonreversible freeway lanes may be darkened when not in operation. The change from normal operation to nonoperation shall occur only when the lane-use control signals display signal indications that are appropriate for the lane use that applies when the signals are not operated. The lane-use control signals shall display signal indications that are appropriate for the existing lane use when changed from nonoperation to normal operations. Also, traffic control devices shall clearly indicate the proper lane use when the lane control signals are not in operation.

Support:
Section 2B.25 contains additional information concerning considerations involving left-turn prohibitions in conjunction with reversible-lane operations.

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