The 29-year-old Spanish man killed in a crash on the inner relief road in Dundalk on Tuesday night was the seventh person to die there since the road opened four years ago.
He was driving a delivery van from Spain to Northern Ireland and has yet to be named by the Garda.
His brother, who was travelling in the passenger seat when the van collided with a car at 11 p.m., was detained overnight at Louth County Hospital.
In 1999, a drunk driver was killed on the road, which bypasses Dundalk, when he collided with a car whose occupants, a young couple, were also killed.
In 1999 also, a young man died in a hit-and-run incident, and last year two people died when an elderly woman driver had a heart attack and crashed into an oncoming car, killing its woman driver.
Insp Gerry O'Brien, who is responsible for Operation Lifesaver in the area, said figures indicated drivers on the stretch had one of the highest speeding rates in the State of late. He believes this is due to the good quality of the road. It is a single lane carriageway, less than half-a-mile long, on the main Dublin/ Belfast route, between the Ballymascanlon roundabout and the racecourse road.
However, Insp O'Brien said that, despite the death of the Spanish man on Tuesday night, road deaths in the area were still five down on this time last year.