Speed limits on State Highway 2 and State Highway 58 are under review, but signs with the proposed lower speed limit have already been erected.

The road signs have changed to 80km from 100kmh, but the NZ Transport Agency (NZTA) public consultation of the new speed limit is still open.

And motorists think that means the new limit is a done deal.

The proposed lower limit is on the section of State Highway 58 from SH2 to the Pauatahanui roundabout.

VIRGINIA FALLON/STUFF The agency says that the signs will have to be changed if the speed limit isn't dropped.

The new 80kmh signs, with digits covered by tape, are on both sides of the off ramp at the intersection of SH2 and S58, as it heads over the Haywards Hill.

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A post on the NZTA Facebook page asking for feedback received derision from one motorist, who said it was "interesting that the 80km signs are already up but covered".

VIRGINIA FALLON/STUFF Covered signs on SH58 at the Haywards Interchange in the Hutt, near Wellington.

The agency responded, saying the 80kmh signs were installed as part of the Haywards interchange exchange works, prior to proposals to have speed limits reduced to 80kmh.

"They have been covered because we have not yet made that speed limit change. If we decide not to go to 80km/h, then the signs will have to be removed and replaced with 100km/h signs."

Consultation ends on April 20.

The admission prompted angry reaction on the agency's Facebook page, with commenters accusing the agency of "box ticking".

Formal consultation on changes in the speed limit are required under the Land Transport Setting of Speed Limits Rule.

As part of the consultation, Porirua City Council was also proposing to lower the speed limit of roads connecting to this section of SH58 to 60kmh.

The consultation is part of a country-wide review on speed limits.

Last month, Upper Hutt Mayor Wayne Guppy was unaware about any proposal to drop limits on SH58 and SH2 but said his council would "have plenty to say" about the matter.

"When Transmission Gully is up and running, SH58 will be the main entrance to the Hutt," he said.

Over the past decade there were more than 200 crashes, causing four deaths and 17 serious injuries, on the 100kmh section of SH58 between SH2 and the Pauatahanui roundabout.