City of Grapevine v. Sipes
In City of Grapevine v. Sipes, 195 S.W.3d 689, 692-95 (Tex. 2006) the Texas Supreme Court considered whether a city's failure to install a traffic signal, after deciding to do so, fell under the portion of subsection 101.060(a)(2) allowing claims to be brought under the TTCA when the absence of a traffic-control device is not remedied within a reasonable time after notice.
Construing subsection 101.060(a)(2) in light of subsection 101.060(a)(1), the court concluded that timing of implementation is discretionary:
"When the City first installs a traffic signal is no less discretionary than whether to install it. The timing of implementation could be affected by the governmental unit's balancing of funding priorities, scheduling, traffic patterns, or other matters; to impose liability for the failure to timely implement a discretionary decision could penalize a governmental unit for engaging in prudent planning and paralyze it from making safety-related decisions. This sort of planning and execution is precisely the type of discretionary act for which the TTCA retains immunity. Thus, when subsections (a)(1) and (a)(2) are read together, (a)(2) logically applies only to those traffic signals that have already been installed." (Id. at 694.)