A 255ft-long (78m) load was moved between Shoreham and Henfield in West Sussex causing disruption to motorists.
The electricity transformer, which is 15ft (4.6m) wide and weighs 331 tonnes, left Shoreham Port at 05:30 GMT and was due to arrive in Wineham Lane at about 13:00.
Drivers were warned roads on the route would be closed throughout the day.
Sgt Dan Pitcher, of the East Sussex Roads Policing Unit, thanked road users “for their patience and understanding”.
“This is a substantial load and to ensure the safety of all motorists we will enforce rolling road closures and periodic full road closures on the route throughout the day,” he said.
- Depart Shoreham Port Left on to A259
- Right into A293 Church Road then Trafalgar Road
- Right on to A270
- Left on to A293 up to Hangleton Interchange then A27 and joining the A23 northbound
- On to the A272 for approx 2.2km
- Left on to Wineham Lane, Henfield
- Left on to the access road for the National Grid, BN5 9AZ.
(From Sussex Police)