Already on the state heritage list, the bridge which crosses the Williams River on Stroud Hill Road has now been placed on Transport NSW's list of timber truss bridges to be conserved.

Transport for NSW has reviewed and updated the list of bridges recognised within the Timber Truss Road Bridges - A Strategic Approach to Conservation.

Also on the list of additional timber truss bridges to be included under the conservation strategy is the Beckers bridge which crosses Webbers Creek at Dunns Crossing at Mount Thorley in Gresford.

The Brig O'Johnston bridge at Clarence Town was already on the list. Both the state and federal governments have committed funding to providing a replacement crossing to the 1880 bridge.

Completed in 1906, the Cooreei bridge is an early example of a Harvey Dare timber truss bridge. Dare trusses were fifth in the five stages of design evolution of NSW timber truss road bridges.

Cooreei bridge is one of 15 historic bridges in the Hunter region constructed before 1905.

Transport for NSW Executive Director Regional and Outer Metropolitan Roy Wakelin-King said timber truss bridges played an important role in the economic development of regional NSW.

"These bridges were ahead of their time when they were built, showcasing leading engineering practices, and connecting local communities to one another," Mr Wakelin-King said.

"Transport for NSW has worked closely with the Heritage Council of NSW to ensure those bridges with strong local ties remain protected and restored as necessary.

"We've reviewed the conservation list of bridges developed in 2012, with eight bridges being added to the list, while seven which did not meet the strategy objectives were removed.

"Conservation will ensure the retained bridges continue to provide safe access for all users, including pedestrians, cyclists, motorists, agricultural vehicles and freight."

Of more than 400 timber truss bridges built between 1860 and 1936, 48 remain, with 39 managed by Transport for NSW.

There are five different types of truss bridges on the list, varying in style, length and truss configuration, with a total of 27 to be conserved, up from 26.

The order of bridges to be replaced will be determined by the condition of the bridge and the road operation requirements. The community will be kept informed throughout the process.

All bridges for retention will be upgraded and strengthened to support the road network without compromising their state heritage values.

More information is available on the RMS website.