Instead of stopping before making a right turn, Malaysian Chan Joo Kiang, 33, slowly made his way across the junction.
He failed to notice motorcyclist Wallace Sabing, 42, coming from the opposite direction. As a result, Mr Sabing slammed into the trailer Chan was transporting, and later died in hospital.
Chan, who was driving a prime mover during the incident, was jailed for six weeks for negligent driving and disqualified from driving in Singapore for five years yesterday.
The court heard that he was driving in the right lane of the two- lane Gul Way near Tuas towards Pioneer Road at around 11.50am on May 7 last year when he spotted another prime mover travelling in the opposite direction.
The two vehicles approached the non-signalised intersection of Gul Way and Gul Circle at around the same time, and both of them wanted to turn right.
The other driver, Mr Muhammad Iskandah Suhaimi, 38, flashed his high beam to signal to Chan that he was giving way so that Chan could turn first.
The intersection was not wide enough for both prime movers to turn at the same time.
Mr Muhammad Iskandah noted that Chan did not stop but continued to make the right turn at a slow speed. He also noticed Mr Sabing travelling on his left before colliding into the left centre portion of Chan's trailer.
Deputy Public Prosecutor Ashraf Hassan said: "Investigations further revealed that before the accused turned right into Gul Circle, he merely slowed down but did not stop to check for oncoming vehicles travelling along Gul Way towards (Ayer Rajah Expressway).
"The deceased had the right of way as he was travelling straight and there is no evidence that he was speeding."
Mr Sabing was taken to Ng Teng Fong General Hospital where he died of multiple injuries about five hours later.
A medical report revealed that he injured his brain and fractured his neck in the accident. For causing the fatal accident by negligent driving, Chan could have been jailed for up to two years and fined.