In addition to heading and altitude assignments, ATC  occasionally issues speed adjustments to maintain the  required separations. For example: “Cessna 30 Alpha, slow to 100 knots.” A pilot who receives speed adjustments is expected to  maintain that speed plus or minus 10 knots. If for any reason  the pilot is not able to accept a speed restriction, the pilot  should advise ATC. At times, ATC may also employ visual separation techniques  to keep aircraft safely separated. A pilot who obtains visual  contact with another aircraft may be asked to maintain visual  separation or to follow the aircraft. For example: “Cessna 30 Alpha, maintain visual separation with  that traffic, climb and maintain 7,000.” The pilot’s acceptance of instructions to maintain visual  separation or to follow another aircraft is an acknowledgment  that the aircraft is maneuvered as necessary to maintain safe  separation. It is also an acknowledgment that the pilot accepts  the responsibility for wake turbulence avoidance. In the absence of radar contact, ATC relies on position reports  to assist in maintaining proper separation. Using the data  transmitted by the pilot, the controller follows the progress of  each flight. ATC must correlate the pilots’ reports to provide  separation; therefore, the accuracy of each pilot’s report can  affect the progress and safety of every other aircraft operating  in the area on an IFR flight plan. Instrument departure procedures are preplanned IFR  procedures that provide obstruction clearance from the  terminal area to the appropriate en route structure and provide  the pilot with a way to depart the airport and transition to the  en route structure safely. Pilots operating under 14 CFR part  91 are strongly encouraged to file and fly a DP when one is  available.  [Figure 10-2] There are two types of DPs: Obstacle Departure Procedures  (ODP), printed either textually or graphically, and Standard  Instrument Departures (SID), always printed graphically. All  DPs, either textual or graphic, may be designed using either  conventional or area navigation (RNAV) criteria. RNAV  procedures have RNAV printed in the title (e.g., SHEAD  TWO DEPARTURE (RNAV)).  ODPs provide obstruction clearance via the least onerous  route from the terminal area to the appropriate en route  structure. ODPs are recommended for obstruction clearance  The radar departure is normally simple. Following takeoff,  contact departure control on the assigned frequency when  advised to do so by the control tower. At this time, departure  control verifies radar contact and gives headings, altitude, and  climb instructions to move an aircraft quickly and safely out  of the terminal area. A pilot is expected to fly the assigned  headings and altitudes until informed by the controller of  the aircraft’s position with respect to the route given in  On IFR departures from airports in congested areas, a pilot  normally receives navigational guidance from departure  control by radar vector. When a departure is to be vectored  immediately following takeoff, the pilot is advised before  takeoff of the initial heading to be flown. This information is  vital in the event of a loss of two-way radio communications  during departure. and may be flown without ATC clearance unless an  alternate departure procedure (SID or radar vector) has  been specifically assigned by ATC. Graphic ODPs have  (OBSTACLE) printed in the procedure title (e.g., GEYSR  THREE DEPARTURE (OBSTACLE), CROWN ONE  DEPARTURE (RNAV)(OBSTACLE)).  SIDs are ATC procedures printed for pilot/controller use in  graphic form to provide obstruction clearance and a transition  from the terminal area to the appropriate en route structure.  SIDs are primarily designed for system enhancement and to  reduce pilot/controller workload. ATC clearance must be  received prior to flying a SID.  ODPs are found in section C of each booklet published  regionally by the AeroNav Products, TPP, along with “IFR  Take-off Minimums” while SIDs are collocated with the  approach procedures for the applicable airport. Additional  information on the development of DPs can be found in  paragraph 5-2-7 of the AIM. However, the following points  are important to remember. Departure Procedures (DPs) Obstacle Departure Procedures (ODP) Radar-Controlled Departures Standard Instrument Departures 1.  The pilot of IFR aircraft operating from locations  where DP procedures are effective may expect an ATC  clearance containing a DP. The use of a DP requires  pilot possession of at least the textual description of  the approved DP. 2.  If a pilot does not possess a preprinted DP or for  any other reason does not wish to use a DP, he or  she is expected to advise ATC. Notification may  be accomplished by filing “NO DP” in the remarks  section of the filed flight plan or by advising ATC. 3.  If a DP is accepted in a clearance, a pilot must comply  with it. 10-5