Minister for Regional Transport and Roads and Member for Bathurst Paul Toole said the NSW Government was investing in McKanes Bridge at South Bowenfels to ensure it remains safe and operational into the future.

"Once complete, the bridge will have a new deck and stronger supports while maintaining the heritage significance of the structure," Mr Toole said.

Built in 1893, the bridge, located on McKanes Falls Road, is one of four timber McDonald truss bridges remaining in NSW.

"The restoration will ensure its conservation," Mr Toole said.

Upgrades include dismantling and restoring existing bridge components that require repair, strengthening the existing truss with new steel and timber elements, strengthening the existing foundations with concrete, as well as final roadworks and landscaping.

Detours will be in place due to the bridge closure, via Jenolan Caves Road and the Great Western Highway, adding five minutes to a journey, Mr Toole said.

Work will be carried out on weekdays from 7am to 6pm and some Saturdays from 8am to 1pm, weather permitting, with the full upgrade expected to be complete by late 2021.

Work will involve the use of machinery and every effort will be made to minimise noise by arranging the work in stages at different locations and turning off machinery when not in use.

Motorists should follow the direction of all traffic control and signs, including reduced speed limits.

For the latest traffic updates, call 132 701, visit livetraffic.com or download the Live Traffic NSW App.