The man was crushed in the cab of the truck, which for unknown reasons slammed into the concrete support of a bridge in Muttenz at around 3.30pm, cantonal police said.
There were no skid marks and the driver had apparently not applied the brakes, police said.
The accident resulted in the closure of the Rothausstrasse in Muttenz, southeast of the city of Basel, for several hours.
In another fatal incident, police in Winterthur are seeking witnesses after a seven-year-old boy riding a bicycle was struck and killed by a truck on a street in the city on Tuesday.
The collision occurred around 5pm on the Tösstalstrasse, police from the city in the canton of Zurich said in a news release.
The circumstances of the accident are not clear, police said.
Counselling services staff were called to the scene to look after the victim's parents and children in the vicinity who saw the accident.
Winterthur police said anyone with information that could shed light on what happened should call 052 267 51 52.