ARTCC. These Center frequency boxes can be used for  finding the nearest frequency within the aircraft range.  They also can be used for making initial contact with the  Center for clearances. The exact location for the Center  transmitter is not shown, although the frequency box is  placed as close as possible to the known location.  During the en route phase, as a flight transitions from one  Center facility to the next, a handoff or transfer of control  is required as previously described. The handoff procedure  is similar to the handoff between other radar facilities, such  as departure or approach control. During the handoff,  the controller whose airspace is being vacated issues  instructions that include the name of the facility to contact,  appropriate frequency, and other pertinent remarks.  Accepting radar vectors from controllers does not relieve  pilots of their responsibility for safety of flight. Pilots must  maintain a safe altitude and keep track of their position,  and it is their obligation to question controllers, request  an amended clearance, or, in an emergency, deviate from  their instructions if they believe that the safety of flight  is in doubt. Keeping track of altitude and position when  climbing, and during all other phases of flight, are basic  elements of situational awareness (SA). Aircraft equipped  with an enhanced ground proximity warning system  (EGPWS), terrain awareness and warning system (TAWS),  or traffic alert and collision avoidance system (TCAS) help  pilots detect and/or correct for potential unsafe proximities  to other aircraft and increases pilot(s) situational awareness.  Regardless of equipment, pilots must always maintain SA  regarding their location and the location of traffic in their  vicinity.  Special high altitude routes allow pilots routing options for  flight within the initial high altitude routing (HAR) Phase  I expansion airspace. Pilots are able to fly user-preferred  routes, referred to as non-restrictive routing (NRR), between  specific fixes described by pitch (entry into) and catch (exit  out of) fixes in the HAR airspace. Pitch points indicate an  end of departure procedures, preferred IFR routings, or  other established routing programs where a flight can  begin a segment of NRR. The catch point indicates where  a flight ends a segment of NRR and joins published arrival  procedures, preferred IFR routing, or other established  routing programs.  The HAR Phase I expansion airspace is defined as that  airspace at and above FL 350 in fourteen of the western  and southern ARTCCs. The airspace includes Minneapolis  (ZMP), Chicago (ZAU), Kansas City (ZKC), Denver (ZDV),  Salt Lake City (ZLC), Oakland (ZOA), Seattle Centers (ZSE),  Preferred IFR routes are established between busier airports  to increase system efficiency and capacity. They normally  extend through one or more ARTCC areas and are designed  to achieve balanced traffic flows among high density  terminals. IFR clearances are issued on the basis of these  routes except when severe weather avoidance procedures  or other factors dictate otherwise. Preferred IFR routes are  listed in the CS and can also be found on www.fly.faa.gov,  which requires entering the following data: departure  airport designator, destination, route type, area, aircraft  types, altitude, route string, direction, departure ARTCC,  and arrival ARTCC. [Figure 2-14] If a flight is planned to or  from an area having such routes but the departure or arrival  point is not listed in the CS, pilots may use that part of a  preferred IFR route that is appropriate for the departure or  arrival point listed. Preferred IFR routes are correlated with  departure procedures (DPs) and STARs and may be defined  by airways, jet routes, direct routes between NAVAIDs,  In conjunction with the HAR program, area navigation  (RNAV) routes have been established to provide for a  systematic flow of air traffic in specific portions of the en  route flight environment. The designator for these RNAV  routes begin with the letter Q, for example, Q-501. Where  those routes aid in the efficient orderly management of air  traffic, they are published as preferred IFR routes.  Additionally, information concerning the location and  schedule of special use airspace (SUA) and Air Traffic  Control Assigned Airspace (ATCAA) can be found at http://  sua.faa.gov. ATCAA refers to airspace in the high altitude  structure supporting military and other special operations.  Pilots are encouraged to file around these areas when they  are scheduled to be active, thereby avoiding unplanned  reroutes around them.  Los Angeles (ZLA), Albuquerque (ZAB), Fort Worth (ZFW),  Memphis (ZME), and Houston (ZHU). Jacksonville (ZJX)  and Miami (ZMA) are included for east-west routes only.  To develop a flight plan, select pitch and catch points  which can be found in the Chart Supplement (CS) based  upon your desired route across the Phase I airspace. Filing  requirements to pitch points, and from catch points, remain  unchanged from current procedures. For the portion of the  route between the pitch and catch points, NRR is permitted.  Where pitch points for a specific airport are not identified,  aircraft should file an appropriate departure procedure (DP),  or any other user preferred routing prior to the NRR portion  of their routing. Where catch points for a specific airport  are not identified aircraft should file, after the NRR portion  of their routing, an appropriate arrival procedure or other  user preferred routing to their destination.  Preferred IFR Routes  High Altitude Area Navigation Routing  2-7 