Guide to Surface Movement Guidance and Control System (SMGCS)

In order to enhance taxiing capabilities in low visibility conditions and reduce the potential for runway incursions, improvements have been made in signage, lighting, and markings. In addition to these improvements, Advisory Circular (AC) 120-57, Surface Movement Guidance and Control System, more commonly known as SMGCS (acronym pronounced 'SMIGS'), requires a low visibility taxi plan for any airport which has takeoff or landing operations with less than 1,200 feet runway visual range (RVR) visibility conditions. This plan affects both air crew and vehicle operators. Taxi routes to and from the SMGCS runway must be designated and displayed on a SMGCS Low Visibility Taxi Route chart.

A brief detail of SMGCS features is listed below but SMGCS airports may not have all of these features. For additional SMGCS information refer to the Aeronautical Information Manual or the particular airport's SMGCS Low Visibility Taxi Route chart.

Stop bars are required at intersections of an illuminated (centerline lighted) taxiway and an active runway for operations less than 600 feet RVR. These lights consist of a row of red unidirectional, in-pavement lights installed along the holding position marking. When extinguished by the controller, they confirm clearance for the pilot or vehicle operator to enter the runway. Controlled stop bars operate in conjunction with green centerline lead-on lights, which extend from the stop bar location onto the runway.

Normal operation of stop bars include:

When ATC issues a clearance to the pilot to enter the runway they activate a timer. This action causes the red stop bar to be extinguished and the green lead-on lights to illuminate.
After traveling approximately 150 feet beyond the stop bar, the aircraft or vehicle activates a sensor. This sensor relights the red stop bar and extinguishes the first segment of the lead-on lights between the stop bar and the sensor. This protects the runway against inadvertent entry by a trailing aircraft or vehicle.
The aircraft then activates another sensor at approximately 300 feet which extinguishes the remaining lead-on lights.
If either sensor is not activated within a specified time limit, the stop bar will automatically reset to "on" and both sets of lead-on lights will be turned "off."

Should the pilot or vehicle operator have a discrepancy between the condition of the stop bar or lead-on lights and the verbal clearance from the controller, the aircraft or vehicle shall stop immediately.

!WARNING!
Pilots Shall Never Cross An Illuminated Red Stop Bar

Runway guard lights, either elevated or in-pavement, will be installed at all taxiways which provide access to an active runway. They consist of alternately flashing yellow lights. These lights are used to denote both the presence of an active runway and identify the location of a runway holding position marking.

Taxiway Centerline lights guide ground traffic under low visibility conditions and during darkness. These lights consist of green in-pavement lights.

ATC will verify the position of aircraft and vehicles using geographic position markings. The markings can be used either as hold points or for position reporting. These checkpoints or "pink spots" will be outlined with a black and white circle and be designated with a number, a letter, or both.

Three yellow in-pavement clearance bar lights will be used to denote holding positions for aircraft and vehicles. When used for hold points, they are co-located with geographic position markings.


	Feature	Description
	Stop Bar Lights	Row of red, in-pavement lights that when illuminated designate a runway hold position. *NEVER CROSS AN ILLUMINATED RED STOP BAR*.
	Runway Guard Lights	Elevated or in-pavement yellow flashing lights installed at runway holding positions.
	Taxiway Centerline Lights	Green in-pavement lights to assist taxiing aircraft in darkness and in low visibility conditions.
	Clearance Bar Lights	In-pavement yellow lights. When installed with geographic position markings they indicate designated aircraft or vehicle hold points.
	Geographic Position Marking (pink spot)	Indicates a specific location on the airport surface.
	Taxiway Centerline Marking	Provides a visual cue to permit taxiing along a designated path. Marking may be enhanced on light-colored pavement by outlining with a black border.

Normal operation of stop bars include:

Feature

Description