EXC/Support Systems/TBT-EXC-016

Excavation Near Live Highways

Excavations › Support Systems › Excavation Near Live Highways

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Excavation adjacent to live highways combines trench collapse risk with exposure to passing traffic.
Vehicle vibration from heavy traffic can destabilise excavation walls, accelerating collapse risk.
Traffic management under Chapter 8 must be in place before any excavation work begins on the highway.
Excavations in the carriageway or verge expose workers to vehicle incursion if barriers are breached.
Surcharge loading from parked vehicles and traffic adjacent to the trench reduces ground stability.
Buried highway services including drainage, ducting, street lighting cables, and traffic signal cables are dense.
Pedestrian diversions must be provided where footways are affected by the excavation works.
Excavation spoil must not obstruct sightlines for approaching drivers or pedestrian crossings.
NRSWA permit requirements apply for all excavation in adopted highways.
Night working may be required to minimise disruption, adding darkness and fatigue to the risk profile.

Dual hazard	Workers face simultaneous risks from trench collapse below and vehicle strikes from the adjacent live carriageway.
Traffic vibration	Heavy vehicle vibration weakens excavation sides, increasing the chance of sudden wall collapse.
Service density	Highway verges and carriageways contain dense concentrations of buried services in close proximity.

Don't

Install Chapter 8 traffic management before starting any highway excavation
Support trench sides to resist both soil pressure and traffic-induced vibration
Locate all buried services using CAT, Genny, and statutory service plans
Obtain the required NRSWA permit before excavating in an adopted highway
Maintain barriers between the excavation and live traffic lanes throughout the work
Provide safe pedestrian diversions where footways are affected by excavation works
Keep spoil heaps away from the carriageway edge to maintain driver sightlines
Inspect the excavation more frequently where traffic vibration affects stability
Brief the team on the combined risks of excavation and live traffic before starting
Backfill and reinstate the highway surface to the specification in the NRSWA permit

DON'T excavate in a highway without Chapter 8 traffic management in place
DON'T leave trench sides unsupported adjacent to a live carriageway
DON'T stack spoil where it obstructs driver sightlines or pedestrian routes
DON'T allow workers to enter the carriageway side of the trench without barriers
DON'T excavate without an NRSWA permit in adopted highway land
DON'T ignore the additional instability caused by traffic vibration on trench walls
DON'T park plant or vehicles between the trench and live traffic without authorisation
DON'T leave open excavations unguarded in the highway during hours of darkness
DON'T reduce barrier protection between the excavation and the live carriageway
DON'T assume shallow excavations in highways are low risk — services are dense and shallow

See also: Excavation Safety Awareness | Working in Live Carriageways

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