HOUSTON — A family who was the unlucky victim of a falling traffic signal won't get any car repair help from the city because state law exempts traffic signals and lights from liability, officials said.

The city of Houston rejected a claim for reimbursement submitted by Lei Zheng and his wife, Hua Yang, stemming from last year's freak accident. Yang and her 4-year-old son were on a shopping trip when the signal fell through the windshield of their Volkswagen Passat. Neither was seriously hurt.

The couple's insurance company paid their claim and they had the car fixed. But the couple wanted the city to reimburse their insurance deductible and some out-of-pocket medical expenses, totaling less than $2,000.

The city notified Zheng that it was immune from such claims.

"I feel quite astonished because it is totally unfair," said Zheng, 35, a biochemistry teacher at the University of Texas Health Science Center. "From the police report, it is clear that it was not our fault. We didn't do anything other than drive on the street."

Harlan Heilman, a manager in the city's claims office, said the city is prohibited from making payment in such cases.

"These things happen on occasion. Like any other (governmental) entity, we have to follow the law. The state Legislature is the body that addresses this issue," Heilman said.

Traffic lights and signs are specifically exempted from liability, with the intent to keep the city from being responsible for accidents that result from a signal going out or a stop sign being knocked down.

Charles "Rocky" Rhodes, professor at South Texas College of Law, said the law probably covers the case of the falling signal as well.

"As a practical matter, governmental entities are hesitant to pay for things when they don't have to," Rhodes said. "The general rule is you cannot sue the state, even if it hurts you."

Governments are not always immune. State law allows for claims if the government was negligent or failed to address a known problem.