Two motorcyclists riding against the flow of traffic on the Seletar Expressway (SLE) were stopped by police officers who were in the process of dealing with another motorcyclist who had been caught speeding.

The riders, who were all issued summonses, were nabbed while The Straits Times was riding with the Traffic Police during a covert enforcement exercise against errant motorists yesterday.

There were 34 violations detected during the operation for offences such as speeding, using a mobile phone while driving and failing to obey traffic signals.

The first driver who was issued a summons while The Straits Times was present had been seen driving a van on the Tampines Expressway while using his phone.

His driver's licence was verified and he was notified of the possible offence he had committed.

The police said drivers were stopped if they were holding the phone and seen to be texting or calling while the vehicle was moving.

In some cases, the driver's phone was seized and the SIM card returned to them. Two motorists were also stopped for speeding on the SLE and Mandai Road.

The officers conducted the operation from 10am to 4pm.

Speeding-related accidents decreased 5.3 per cent from 360 in the first half of last year to 341 in the same period this year.

The number of drink-driving accidents fell 25.6 per cent from 90 to 67 in that same timeframe.

But fatal accidents involving motorcyclists increased 24.1 per cent to 36 in the first half of this year from 29 in the same period last year.

The top three traffic offences detected during covert operations held between January and last month were speeding, using mobile communication devices while driving and failure to keep left.

"Road safety is a shared responsibility. (The Traffic Police) would like to urge all motorists to adopt good road sense to keep Singapore roads safer for everyone," the police said.