The FAA's Air Traffic Control Order (JO 7110.65W, at paragraph 7-6-1) and the Aeronautical Information Manual (paragraph 4-1-18) both define basic radar service for VFR aircraft includes safety alerts (see the sidebar on page 8), traffic advisories, limited radar vectoring
(on a workload-permitting basis) and sequencing (at locations where procedures have been established).
According to the FAA's Instrument Procedures Handbook, FAA-H-8261-1A, and as discussed above, "When ATC is radar vectoring
to the final approach course, or to the intermediate fix as may occur with RNAV standard instrument approach procedures, ATC may specify in the approach clearance "cleared straight-in (type) approach" to ensure that the pilot understands that the procedure turn or hold-in-lieu-of-PT is not to be flown."
(2) Where other navigation equipment is required to complete the approach, e.g., VOR, ILS, or other non-ADF approaches requiring ADF or DME for the missed approach, use: 'Chart note: ADF required,' or 'Chart note: DME required.' When radar vectoring
is also available, use: 'Chart note: ADF or Radar required.' "
It's used by ATC for radar vectoring
only upon the controller's determination that an adequate radar return is being received.
Doing it in a quick GA airplane like a Cirrus SR22 still consumes between four and six hours because of all the radar vectoring
and ground delays.
When ATC is radar vectoring
to the final approach course or to the Intermediate Fix, ATC may specify in the approach clearance 'CLEARED STRAIGHT-IN (type) APPROACH' to insure the procedure turn or hold-in-lieu-of-PT is not to be flown.
But there is also something called an "approach gate" along every final approach course, before the final approach segment, whenever radar vectoring
is in progress.