Two years ago the RTA was so concerned about child safety on Mirrool Road that its state-wide priority list ranked the site fourth in line to receive the safety measure.

But according to the latest rankings, the busy road has fallen out of the top 75 in a decision that has baffled Griffith City Council.

Adding to the confusion is that the RTA has rejected an offer from Casella Wines to pay about $25,000 to have the lights installed.

Councillor Doug Curran, the chairman of the traffic committee, said he had written to the NSW Roads Minister David Borger seeking clarification.

"We're at a bit of a loss to be honest," Cr Curran said.

"We were told a few years ago we were in the top 10 and now they just keep going further and further down."

Cr Curran said the success of Casella Wines in recent years had meant the school precinct had become increasingly polluted with heavy vehicles.

But he said when the winery approached the RTA it was told it did not accept such offers, despite council having information that at least 25 schools in Sydney had privately funded flashing lights.

"Here we have a local trying to do the right thing by the community but for some stupid, ridiculous reason the RTA won't allow it," Cr Curran said.

An RTA spokesperson refused to clarify the organisation's policy on private funding, but indicated there were concerns over the ongoing maintenance of privately funded safety infrastructure.

"The RTA has no formal record showing Mirrool Avenue at Yenda Public School ranked as described, but will carry out an investigation of this site," the spokesperson said.

"The ranking of schools for flashing light treatment is done on a state-wide basis and in accordance with road safety criteria.

"The purchasing and installation of flashing lights is only part of the life time cost of the lights. There are also ongoing costs for monitoring and maintenance."