§ 101.056.Discretionary Powers

The discretionary function exclusion, and it is the one most often decisive.

The chapter does not apply to a claim based on:

(1) the failure of a governmental unit to perform an act that the unit is not required by law to perform; or (2) a governmental unit's decision not to perform an act, or its failure to make a decision on the performance or nonperformance of an act, if the law leaves that to the discretion of the governmental unit.

The second is the substantial one, and note that it covers indecision as well as decision. A governmental unit that decides not to act is protected, and so is one that never decides at all — an omission that would otherwise be the easiest thing to characterise as negligence.

The recurring distinction is between policy and implementation. Deciding whether to install a traffic signal, where to place a guardrail, or how to allocate a maintenance budget is discretionary. Carrying out a decision already made — maintaining the signal that was installed — is operational, and the exclusion does not protect it.

The reasoning is that discretionary decisions involve weighing cost, risk, and competing public needs. A court assessing them in a damages suit would be substituting its judgment for the body that has the information and the political accountability.

The first subdivision is narrower and almost tautological: a governmental unit is not liable for not doing what no law required it to do.

The traffic device section applies the same policy-implementation line to signs and signals specifically.