red lights on each side. A controlled stop bar is operated in  conjunction with the taxiway centerline lead-on lights which  extend from the stop bar toward the runway. Following the  ATC clearance to proceed, the stop bar is turned off and the  lead-on lights are turned on. The stop bar and lead-on lights  are automatically reset by a sensor or backup timer.  Similar to runway lighting, taxiways also have various lights  which help pilots identify areas of the taxiway and any  surrounding runways.  Obstructions are marked or lighted to warn pilots of  their presence during daytime and nighttime conditions.  Obstruction lighting can be found both on and off an airport  to identify obstructions. They may be marked or lighted in  any of the following conditions.  Omnidirectional taxiway lights outline the edges of the  taxiway and are blue in color. At many airports, these  edge lights may have variable intensity settings that may  be adjusted by an ATC when deemed necessary or when  requested by the pilot. Some airports also have taxiway  centerline lights that are green in color.  Clearance bar lights are installed at holding positions on  taxiways in order to increase the conspicuity of the holding  position in low visibility conditions. They may also be  installed to indicate the location of an intersecting taxiway  during periods of darkness. Clearance bars consist of three  in-pavement steady-burning yellow lights.  Runway guard lights are installed at taxiway/runway  intersections. They are primarily used to enhance the  conspicuity of taxiway/runway intersections during low  visibility conditions, but may be used in all weather conditions.  Runway guard lights consist of either a pair of elevated flashing  yellow lights installed on either side of the taxiway, or a row of  in-pavement yellow lights installed across the entire taxiway,  at the runway holding position marking.  Note: Some airports may have a row of three or five  in-pavement yellow lights installed at taxiway/runway  intersections. They should not be confused with clearance  bar lights described previously in this section.  Stop bar lights, when installed, are used to confirm the ATC  clearance to enter or cross the active runway in low visibility  conditions (below 1,200 ft Runway Visual Range (RVR)).  A stop bar consists of a row of red, unidirectional, steady- burning in-pavement lights installed across the entire taxiway  at the runway holding position, and elevated steady-burning  REL provide a warning to aircraft crossing or entering a  runway from intersecting taxiways that there is conflicting  traffic on the runway. THL provide a warning signal to  aircraft in position for takeoff that the runway is occupied  and it is unsafe to take off. As of 2016, the RWSL system is  operational at 14 of the nation’s busiest airports with 3 more  airports scheduled to receive the system by 2017.  Runway status lights are red in color and indicate runway  status only; they do not indicate clearance to enter a runway  or clearance to takeoff. The RWSL system provides warning  lights on runways and taxiways, illuminating when it is unsafe  to enter, cross, or begin takeoff on a runway. Currently, there  are two types: Runway Entrance Lights (REL) and Takeoff  Hold Lights (THL).  [Figures 14-35  and  14-36]  A top priority of the FAA is to continue to enhance airport  safety while maintaining airport capacity. Reducing runway  incursions is a major component of this effort. Runway  incursions develop quickly and without warning during routine  traffic situations on the airport surface, leaving little time for  corrective action. The Runway Status Lights (RWSL) System  is designed to provide a direct indication to you that it is unsafe  to enter a runway, cross a runway, or takeoff from or land on  a runway when the system is activated.  Taxiway Lights  Obstruction Lights  Omnidirectional  Clearance Bar Lights  Runway Guard Lights  Stop Bar Lights  New Lighting Technologies  14-19  • Red obstruction lights—flash or emit a steady red  color during nighttime operations, and the obstructions  are painted orange and white for daytime operations.  • High intensity white obstruction lights—flash high  intensity white lights during the daytime with the  intensity reduced for nighttime.  • Dual lighting—a combination of flashing red beacons  and steady red lights for nighttime operation and high  intensity white lights for daytime operations.  Figure 14-34.  Radio controlled runway lighting.  Function Key Mike  Highest intensity available  Medium or lower intensity (Lower REIL or REIL off)  Lowest intensity available (Lower REIL or REIL off)  7 times within 5 seconds  5 times within 5 seconds  3 times within 5 seconds 