Two state highway bridges in west Waikato that will introduce new weight restrictions for heavy vehicles from 1 November 2021 will not have advisory signs installed in time for that date.

The Kopaki rail overbridge on SH30 will be restricted to vehicles under six tonnes and the Mangaotama Stream bridge on SH39 will be restricted to vehicles that are less than 50% of Class 1.

Due to manufacturing delays, the signs are not expected to be installed until at least 15 November.

Regardless of the manufacturing delay, Waka Kotahi is asking drivers to comply with the new weight limits, which are intended to keep both bridges safe for all traffic that use them.

The recommended detour for vehicles over 50% of Class 1 travelling between Otorohanga and north of Hamilton is SH3 and SH1 through Te Awamutu and Hamilton.

A detour is available at the bridge for local heavy traffic using Meadway Road, Hams Road, Forkert Road and Ngahinapouri Road. This detour is not advised for through traffic as it is narrow with single lane bridges.

The timber Kopaki rail overbridge, about 23km south of Te Kuiti on SH30, is currently restricted to 80% of Class 1. However a further restriction is required to ensure it can remain open to light traffic while the replacement bridge is under construction. The new bridge, which will be able to be used by all heavy traffic, will be completed in 2023.

Trucks travelling between Te Kuiti and Maniaiti/Benneydale will need to use the existing heavy traffic bypass of SH4 and Kopaki Road.