Does the term track guidance apply only to conventional procedures? In ICAO's 8160 "Aircraft Operations" manual there is a term called "track guidance", for which I can not find any clear definition.

A few examples:


  Departure Procedures 3.1
  
  3.1.1 There are two basic types of departure route: straight and turning.
  
  3.1.2 Track guidance shall be provided:
  
  a) withing 20.0 km (10.8 NM) from the departure end of the runway (DER) for straight departures; and
  
  b) within 10.0 km (5.4 NM) after completion of turns for turning departures.
  
  3.1.3 Surveillance radar may be used to provide track guidance.


..


  3.2.2 Types of Straight departure
  
  b) straight departure with track guidance:
  
  1) facility ahead or behind; and
  
  2) offset (track parallel/track offset/track crossing).


..


  1.6 TRACK GUIDANCE
  
  1.6.1 Track guidance should normally be provided for all phases of flight through the arrival, initial, intermediate,
  final and missed approach segments. When track guidance is provided, the appropriate segment shall lie within the
  established coverage of the navigation facility on which the track guidance is based.


Judging from the context in which track guidance is mentioned, I would say that it refers to conventional navaid-based procedures, where the aircraft needs navaid facilities in order to keep on track.

All things considered, does the term track guidance have any meaning for RNAV/RNP procedures? Are RNAV/RNP procedures considered procedures without track guidance?

Any clarification would be appreciated.
ICAO Doc 8168 "Procedures for Air Navigation Services - Aircraft Operations - Volume I - Flight Procedures" states under 2.1.3 Types of SID:


  Track guidance may be provided by a suitably located facility (VOR or NDB) or by RNAV.


To answer your question: RNAV/RNP SIDs are considered procedures with track guidance.

The better your tracking is the smaller the protection area required (especially for turn construction). So flying inbound or outbound a navaid or having RNAV capabilities greatly increases your precision und therefore allows for procedure construction with relaxed climb gradients in areas with difficult obstacle situation.