AIM 8/15/19  7/16/20  4 − 3 − 18. Taxiing REFERENCE − NOTE − NOTE − a. General. Approval must be obtained prior to moving an aircraft or vehicle onto the movement area during the hours an Airport Traffic Control Tower is in operation. 1. Always state your position on the airport when calling the tower for taxi instructions. 2. The movement area is normally described in local bulletins issued by the airport manager or control tower. These bulletins may be found in FSSs, fixed base operators offices, air carrier offices, and operations offices. 3. The control tower also issues bulletins describing areas where they cannot provide ATC service due to nonvisibility or other reasons. 4. A clearance must be obtained prior to taxiing on a runway, taking off, or landing during the hours an Airport Traffic Control Tower is in operation. 5. A clearance must be obtained prior to crossing any runway. ATC will issue an explicit clearance for all runway crossings. 6. When assigned a takeoff runway, ATC will first specify the runway, issue taxi instructions, and state any hold short instructions or runway crossing clearances if the taxi route will cross a runway. This does not authorize the aircraft to “enter” or “cross” the assigned departure runway at any point. In order to preclude misunderstandings in radio communica- tions, ATC will not use the word “cleared” in conjunction with authorization for aircraft to taxi. 7. When issuing taxi instructions to any point other than an assigned takeoff runway, ATC will specify the point to taxi to, issue taxi instructions, and state any hold short instructions or runway crossing clearances if the taxi route will cross a runway. ATC is required to obtain a readback from the pilot of all runway hold short instructions. 8. If a pilot is expected to hold short of a runway approach/departure ( Runway XX  APPCH/ Runway XX  DEP) hold area or ILS holding position (see FIG 2 − 3 − 15, Taxiways Located in Runway Approach Area), ATC will issue instructions. 9. When taxi instructions are received from the controller, pilots should always read back: (a) The runway assignment. (b) Any clearance to enter a specific runway. (c) Any instruction to hold short of a specific runway or line up and wait. 10. Controllers are required to request a readback of runway hold short assignment when it is not received from the pilot/vehicle. b. ATC clearances or instructions pertaining to taxiing are predicated on known traffic and known physical airport conditions. Therefore, it is important that pilots clearly understand the clearance or instruction. Although an ATC clearance is issued for taxiing purposes, when operating in accordance with the CFRs, it is the responsibility of the pilot to avoid collision with other aircraft. Since “the pilot − in − com- mand of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft” the pilot should obtain clarification of any clearance or instruction which is not understood. AIM, Para 7 − 4 1 , General 1. Good operating practice dictates that pilots acknowledge all runway crossing, hold short, or takeoff clearances unless there is some misunder- standing, at which time the pilot should query the controller until the clearance is understood. Air traffic controllers are required to obtain from the pilot a readback of all runway hold short instructions. 2. Pilots operating a single pilot aircraft should monitor only assigned ATC communications after being cleared onto the active runway for departure. Single pilot aircraft should not monitor other than ATC communications until flight from Class B, Class C, or Class D surface area is completed. This same procedure should be practiced from after receipt of the clearance for landing until the landing and taxi activities are complete. Proper effective scanning for other aircraft, surface vehicles, or other objects should be continuously exercised in all cases. 3. If the pilot is unfamiliar with the airport or for any reason confusion exists as to the correct taxi routing, a request may be made for progressive taxi instructions which include step − by − step routing directions. Progressive instructions may also be issued if the controller deems it necessary due to traffic or field conditions (for example, construction or closed taxiways). Airport Operations 4 − 3 − 23