Is a public entity or a public employee liable under government code section 830.30.6 for injuries sustained by a person who was injured in a motor vehicle accident as a result of injuries sustained while driving under a traffic light?

Government Code section 830.6 defines the second element - discretionary approval - as consisting of either of two parts: "Neither a public entity nor a public employee is liable under this chapter for an injury caused by the plan or design of a construction of, or an improvement to, public property where [first part] such plan or design has been approved in advance of the construction or improvement by the legislative body of the public entity or by some other body or employee exercising discretionary authority to give such approval or where [second part] such plan or design is prepared in conformity with standards previously so approved . . . ." "A detailed plan, drawn up by a competent engineering firm, and approved by a city engineer in the exercise of his or her discretionary authority, is persuasive evidence" that the requirements of the first part have been met. (Grenier v. City of Irwindale (1997) 57 Cal.App.4th 931, 940.)