RITTRs
Update: 2017-02-23 I can’t find anything in the AIM or FAA docs about RITTRs so I suspect that they never happened or were test areas for Terminal Arrival Areas (TAA).
From the Piper Flyer article RITTRs Understood.
“The NPRM defines a RITTR as a low altitude route based on Area Navigation for GPS-equipped aircraft designed to expedite the handling of IFR overflight traffic through busy terminal airspace areas. From this definition emerge three key concepts that pilots wishing to use these routes should understand.
First, RITTRs are only available to GPS-equipped aircraft. Although the NPRM specifically referenced their availability to aircraft eligible to file “/G” in their flight plan, the routes are also available to aircraft that file “/E” and “/F.” The latter two prefixes are for aircraft equipped with Flight Management Systems.
Second, RITTRs exist only in the vicinity of Class B or other highly congested airspaces. You can spot these routes on NACO and Jeppesen low-en route charts as they are the airways charted in blue, instead of the traditional black. They have the prefix “T” (for Tango) and a number between 200 and 500. They are not less than 12, nor more than 500, nautical miles in length. The minimum length requirement appears to be based on issues of chart clutter, but the rationale for the maximum length restriction is not so clear.
Third, because they are GPS-based, they are charted with a Minimum En route Altitude containing a “G” suffix (i.e., 2800G). This MEA may be lower than the MEAs for nearby Victor airways because the RITTR does not depend on receiving signals from VORs, which are often subject to constraints dictated by local geography. A RITTR may also be charted with a Maximum Authorized Altitude (MAA). For example, T213, located to the west of Cincinnati, has an MAA of 8000. MAAs may be necessitated by the arrival and departure paths commonly used at the underlying airport.
Note that although RITTRs are defined by GPS coordinates, the starting and ending points will always be located within Victor airways. In other words, a RITTR will not have a GPS en route fix as its starting or ending location; instead, it will intersect a Victor airway. The stated purpose for this requirement, according to the NPRM, is “to provide connectivity between the RITTR and the low altitude en route structure.””