There is no single ironclad test the courts use in determining whether a delay in adjudicating an immigration petition is unreasonable. The closest thing we have are the so-called TRAC factors. These factors are guidance from the seminal case, Telecommunications Research & Action Center v. Federal Communications Commission 750 F.2d 70 (D.C. Cir. 1984).
While TRAC v. FCC is not an immigration case, the standard from the case has been widely applied to agency delay cases involving immigration.
The TRAC factors are:
(1) The time agencies take to make decisions must be governed by a “rule of reason”;
(2) where Congress has provided a timetable or other indication of the speed with which it expects the agency to proceed in the enabling statute, that statutory scheme may supply content for this rule of reason;
(3) delays that might be reasonable in the sphere of economic regulation are less tolerable when human health and welfare are at stake;
(4) the court should consider the effect of expediting delayed action on agency activities of a higher or competing priority;
(5) the court should also take into account the nature and extent of the interests prejudiced by delay; and,
(6) the court need not find any impropriety lurking behind agency lassitude in order to hold that agency action is unreasonably delayed.