A total of 149.2 million tonnes of goods was transported by road last year, new figures from the Central Statistics Office show, an increase of 1.4% on the 2017 total.
But the CSO said that activity measured as weight by distance was 11,445 tonne-kilometres in 2018, a decrease of 2.7% compared with 2017.
The total distance covered by road freight transport in 2018 was 1.6 billion kilometres.
The commodity group "Quarry products, metal ores and peat" represented 28.1% of all tonnes carried during the year.
Today's CSO figures also show that a total of 32.8 million tonnes of goods was transported by road in the fourth quarter of 2018 - a drop of 7.9% on the same time in 2017.
There were an estimated 118,032 Irish registered goods vehicles (greater than 2 tonnes unladen weight) operating in Ireland and abroad in 2018.
This marked an 8.8% increase on 2017.