Preventing Vehicle-Aircraft Incidents During Winter Operations and Periods of Low Visibility (2008)

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For years, the method used to avoid runway and airfield inci- dents during low visibility and winter operating conditions was based primarily on human communication, the alertness of operators and controllers, and written SOPs or regulations. The advancement of technology has created potential to better mitigate the effects of human and operational errors at airports, especially during winter operations. A number of public and private technologies have been proposed and studied over the years. The technologies follow one of two paths for preventing incursions: one is detection and the other is avoidance. Detection relies on technology to detect a possible incursion and provide an alert to ATC, while avoidance technologies prompt an alert to an aircraft or vehi- cle operator to not enter a restricted area. Runway safety technologies that have been considered, are being studied, or are being used for purposes of enhancing safety at airports follow: • Airport surface detection equipment model 3 (ASDE-3), • Airport movement area safety systems (AMASS), • Airport surface detection equipment-X (ASDE-X), • Airport target identification system (ATIDS), • Automated dependent surveillance-broadcast (ADS-B), • Runway status lights (RWSL), • Low cost surface surveillance (LCSS), • Loop detection technology (LOT), • Final approach runway occupancy signal, • Driver-enhanced vision systems (DEVS), • Motion sensing systems, and • Other technology. The unique operating conditions of winter can create a challenge for the implementation of any incursion technol- ogy. Although certain technology is being utilized or implemented, it is not clear from the literature search the extent to which winter operational conditions were consid- ered or evaluated as part of the testing. Any consideration of technology intended to help prevent incursions must take into consideration the effects of snow banks, blowing snow, or freezing precipitation, as well as operational con- ditions of numerous vehicles on the movement areas mak- ing quick starts, stops, and turns, and working in groups or singularly. Such conditions are clearly an area for further study and evaluation. Listed below are short summaries of the technology. 44 AIRPORT SURFACE DETECTION EQUIPMENT MODEL 3 Airport surface detection equipment (ASDE) is a ground- surveillance radar that depicts aircraft and airport vehicles and equipment on the airport surface. ASDE-3 is a ground- mapping radar that provides air traffic controllers with a video display of all vehicles and obstacles on an airport’s runways and taxiways. It aids controllers in the orderly movement of aircraft and ground vehicles on the airport surface, especially during periods of low visibility such as rain, fog, and night operations. For ASDE-3 to prevent incursions or conflicts on the ground, a controller must monitor the screen. AIRPORT MOVEMENT AREA SAFETY SYSTEM In conjunction with ASDE-3, the installation of additional safety logic software will sound an alarm to warn controllers of a potential collision or incursion. The software addition is called airport movement area safety system (AMASS). AMASS extends and enhances the capability of the ASDE-3 radar by providing automated alerts and warnings to potential runway incursions and other hazards, thereby assisting the controller’s vigilance. The visual and aural prompts require controllers to respond to situations that potentially compromise safety. AIRPORT SURFACE DETECTION EQUIPMENT-X An enhanced version of airport surface detection equipment, called “ASDE-X,” is intended to address small- to medium- sized airports. It is a less-expensive ground radar and warning system than ASDE-3 radar and AMASS. ASDE-X integrates a combination of surface movement radar and transponder multi-lateration sensor antennas placed around an airport to detect and show aircraft and vehicle positions on an ATC tower display. The system detects and alerts controllers to potential aircraft and vehicle collision situations through advanced conflict detection and alerting technology. An ASDE-X dis- plays an identification tag next to every radar target depicted on a ground controller’s display. AIRPORT TARGET IDENTIFICATION SYSTEM An airport target identification system (ATIDS) provides con- trollers with aircraft and vehicle identification and position on CHAPTER TEN PAST, CURRENT, AND FUTURE TECHNOLOGICAL DEVELOPMENTS

45 the airport movement area and in selected ramp and gate areas as a means to augment existing ASDE/AMASS sys- tems. It has become part of the Runway Incursion Reduction Program. LOW COST SURFACE SURVEILLANCE Low cost surface surveillance (LCSS) systems are vehicle- tracking systems that utilize global positioning system (GPS), microwave technology, or changes in the earth’s magnetic field. They are beginning to make inroads into aviation oper- ations. Some are an extension of existing ground fleet vehicle management systems while others are expansion of the GPS revolution (61, 62). AUTOMATIC DEPENDENT SURVEILLANCE-BROADCAST Automatic dependent surveillance-broadcast (ADS-B) is a cooperative surveillance system that uses satellite technology, vehicle and aircraft avionics, and a flexible ground infra- structure to more accurately and quickly transmit information between aircraft and air traffic control. “Automatic” means that the system is always on and requires no operator inter- vention. “Dependent” means it depends on an accurate global navigation satellite system (GNSS) signal for position data. “Surveillance” reflects its radar-like observational capabili- ties and services. Broadcast means the system continuously broadcasts aircraft position and other data to any aircraft, vehicle, or ground station equipped to receive ADS-B. With ADS-B, aircraft and vehicles will be able to receive data about each other’s whereabouts directly, rather than through ATC intercession. It will display in the cockpit or cabin the location of aircraft and vehicles on and in the vicinity of an airport. RUNWAY STATUS LIGHTS The runway status lights (RWSL) system is a series of lights (hold position, runway and taxiway lead-on centerline, and elevated runway guard lights) that inform controllers, pilots, and vehicle operators whether or not a runway is clear (63, 64). Used in conjunction with ASDE-3 and ASDE-X, RWSL safety logic software assesses any possible conflicts with other surface traffic. Red in-pavement runway entrance lights are illuminated if the runway is unsafe for entry or crossing, and red in-pavement runway centerline hold lights are illuminated if the runway is unsafe for arrival or departure. The vehicle or aircraft operator then responds to the signal. GLOBAL POSITIONING SYSTEM VEHICLE TRACKING GPS satellite vehicle tracking systems, also known as auto- matic vehicle locators (AVL), have been utilized in highway traffic management systems for several years. Several com- panies have adapted it to airports (65, 66). On-board processors mounted to each vehicle help track their location. The vehi- cles communicate over a radio or cellular digital packet data system to a base station where a computer monitors fleet activity and processes captured data for post-analysis. Each may be clicked on to see precisely which vehicle is at which location, what it is doing, and how it is performing. All data are recorded and can be played back on the computer. GPS also allows for vehicles to be monitored through means of a web browser cartography program such as Google Earth or Mapquest. The computer monitor can be located in the operations office, the ATCT, or even the vehicles themselves. The monitored vehicles then appear as small traversing dots on the screen. Other GPS tracking systems are passive in that a simple GPS receiver is displayed over an airport’s geo- graphical information system layout of the airport (67). LOOP TECHNOLOGY Loop technology (LOT) is a common method for detecting objects as they pass over a given position by creating an inductive electrical charge in a wire or sensors embedded in the pavement. LOT is used throughout the nation for roadway vehicle traffic monitoring and control. LOT has the potential to be used in a stand-alone mode or as a supplemental sensor input to an ASDE radar surface surveillance system. It can also be conveyed to the vehicle operator as an in-cabin warn- ing monitor (68). FINAL APPROACH RUNWAY OCCUPANCY SIGNAL Final approach runway occupancy signal is a pilot notifica- tion system that provides warning to aircraft pilots on final approach when vehicles or other aircraft are actively on the runway through inductive loop sensors embedded in the runway and taxiway surfaces to track aircraft and vehicles entering and exiting the monitored zones. When any moni- tored zone on the runway is occupied by a stationary or slow- moving target, such as a snow plow, a signal is provided to pilots on approach to landing by flashing the precision approach path indicator lights as a visual indication to pilots on approach (69). The monitoring system can use LOT, multi- lateration, or similar technology to detect the presence of equipment, vehicles, or aircraft. DRIVER-ENHANCED VISION SYSTEMS DEVS can consist of night vision enhancement devices and night vision imaging systems that can provide drivers with some ability to see at night for enhanced operations (70, 71). Night vision goggles are a main component of night vision imaging systems. Interior and exterior cabin lighting, cabin control layout, and vehicle windows are secondary compo- nents. Based on survey responses, night vision enhancement devices and night vision imaging systems are not currently

being used at airports in snowplowing operations and its potential utility is unclear. Enhanced vision systems typically use imaging sensors to penetrate weather phenomena such as darkness, fog, haze, rain, or snow; the resulting enhanced scene, a sensor image, is pre- sented on a head-up display (72). The display is normally projected onto the windshield or through a separate display. The use of head-up displays in snow removal vehicles may be an issue, however, as their use demands an undue amount of attention and makes them prone to such adverse effects as distortion, luminance contrast differences, dark adaptation inhibition, and object misrepresentation (73, 74). MICROWAVE MOTION SENSORS Microwave motion sensors consist of microwave transmit- ters located at the hold lines of runways or wherever vehicles need to be monitored. The transmitters can selectively detect incoming or outgoing traffic and send a signal to an enunci- ator located in the ATCT or elsewhere. A receiver device in a vehicle could play a prerecorded voice warning, or transmit an audio or light warning to the driver in response to each of the signals sent by the microwave transmitters. The microwave transmitters are impervious to weather conditions (75, 76). GROUND MARKER SYSTEM A ground marker system is designed to transmit locally a voice message to the cockpit of an airplane or the cabin of a vehicle to alert the operator of his or her position on the airport sur- face. The system is activated when an aircraft or vehicle is detected by inductive loops in the pavement. An in-cab vehicle warning system using wireless communication supported by dedicated short-range communications is also being investi- gated. Dedicated short-range communications is the technol- ogy used on toll highways for recognizing vehicles. As applied to airports, dedicated short-range communications data can be transmitted from a runway edge monitor or taxiway sensor to a vehicle in-cab alerting system (rather than to the marker system used for arriving aircraft) to warn the driver that it is not safe to enter a runway or other airport surface (76). LASER LIGHT HOLD LINES A laser enhancement program functions by projecting a bright light across the first solid line of the hold position markings thereby emphasizing the hold position markings. The laser and optic assembly device straddles the end of a hold line and projects a line or shaped beam of laser light along the surface. When shown in adverse weather conditions such as rain, snow, or fog, it creates a low profile three-dimensional line that is far more noticeable than traditional low visibility lighting aids. The technology has the capability to project lines in red and yellow laser illuminations. In areas that are subject to snow 46 accumulations that can cover up painted markings, the laser lines could convey the location, layout, color, and importance of these markings (76, 77). ADDRESSABLE MESSAGE BOARDS A 2002 demonstration project installed addressable electronic signs that could display programmed advisory messages on an LED display at taxiway/runway intersections or other areas of interest. Its intent is to supplement standard hold position signs, address problematic areas on an airport, or convey SA information to ground operators (76). IN-GROUND LIGHT EMITTING DIODE The in-ground LED is a commercial transportation-grade LED light strip encased in a linear strip of clear plastic and placed along hold lines. The intent of the in-ground LED light strips is to accentuate runway and taxiway signage and markings (i.e., hold-short lines) that may become obscured during low light and low visibility weather conditions (76). Although functional in low visibility situations, it is not clear how they would function in snow removal situations. RUNWAY GUARD LIGHTS Runway guard lights (RGL) are currently required by the FAA for airports that have an approved SMGCS plan for conduct- ing operations during low visibility conditions or at airports that have an operational need. The RGLs enhance the standard visual cues, signs, and markings used to mark the location of the holding position. Because RGLs are an international stan- dard and are visible in both day and night operations, RGLs provide added surface safety during all weather conditions. ENHANCED RUNWAY LEAD-ON LIGHTS Effective February 1, 2007, Advisory Circular 150/5340-30C, Design and Installation Details for Airport Visual Aids, changed runway lead-on light standards to include a modi- fied color pattern of taxiway centerline lead-on lights (78). The modification requires alternating yellow and green lights from the hold-short line to and from the runway to indicate a runway environment. On the taxiway, the centerline lights are green up to the hold-short line. ENHANCED TAXIWAY SURFACE MARKINGS Advisory Circular 150/5340-1, Standards for Airport Mark- ings, was issued in April 2005, requiring airfield markings standards to change to enhance markings effective June 30, 2008, for airports with 1.5 million or more annual passenger enplanements (79). In August 2007, FAA initiated an indus- trywide call to action that recommended all 14 CFR Part 139 airports install enhanced taxiway and hold-short markings,

47 regardless of the number of passenger enplanements. To sup- port the call to action, the FAA has since issued Change 1 to the Advisory Circular requiring the enhanced markings at all 14 CFR Part 139 airports (80). The use of surface-painted holding position signs is required for airports having multi- ple runways, taxiway widths greater than 200 ft, or as deter- mined by other operational need. SUMMARY The previous chapters three through nine expounded on the fac- tors that contributed to the possibility of increased collision risk or runway incursion. Chapter ten highlights the advance- ment of technology as potential means to mitigate the effects of human and operational errors at airports. The chapter pro- vides a synopsis of past technology that had been explored but not adopted, existing technology that is in use, and promis- ing future technology that can address several of the factors identified in this report. The technology follows one of two paths for preventing incursions: technology designed for detec- tion and technology designed for avoidance. Although various technologies are being considered, one obstacle to overcome is the feasibility of usage during winter operations, which places a unique operating condition on each technology. This is an area for further research and study.