Dressed in black jackets and riding black motorcycles, these "bikers" give motorists a shock when they turn on their lights and sirens and reveal their true identities.

The covert officers have been on their bikes on Singapore's roads since last month in the latest attempt by the Traffic Police to clamp down on road offenders - particularly errant motorcyclists.

Explaining the initiative, TP commander Sam Tee said it was not easy for officers to go after motorcyclists in unmarked cars, as they can lose sight of them in heavy traffic.

The 900cc "stealth bikes", on the other hand, are much more manoeuvrable. "Our strategy has evolved. We are matching vehicle type for vehicle type," said Senior Assistant Commissioner Tee.

Bikers are an area of concern for the TP. They have held community events and media campaigns to warn them about the dangers of reckless riding in the past year.

TP statistics show that last year, 4,875 motorcyclists and pillion riders were injured, a 5 per cent rise from 2014. This group also accounted for almost half of all road deaths last year - 72 out of a total of 152.

To address the problem, the TP have increased enforcement to target what they call a "small minority" of motorists and motorcyclists who misbehave.

In their first month of operations, TP's stealth motorcycle officers detected more than 700 violations - including offences such as using a mobile phone while riding and reckless riding. Covert operations - which also included officers in unmarked vehicles - detected 2,653 violations in the first six months of this year, up from 1,048 in the same period last year.

The Straits Times accompanied the TP's Special Operations Team (SOT) on their stealth bikes yesterday - during which three drivers and three motorcyclists were stopped in the course of an hour.

Starting from the TP's headquarters in Ubi, the two-man team took a route through the PIE, up the BKE to Woodlands, before turning back.

One van driver was spotted not wearing a seat belt; a car driver was using his phone. Motorcyclists were spotted speeding and weaving in and out of traffic recklessly.

Virtually all those caught seemed surprised when pulled over. Officers said that when the new bikes were launched, drivers sometimes initially refused to stop. Senior Staff Sgt Pardeep Dass, 31, said: "They always imagine TP officers to be in white uniforms, but once they see us in full gear they know we are police officers and comply."

Underneath their black jackets, the officers wear the white TP uniform and carry their warrant cards.

The SOT's officer commanding, Assistant Superintendent Firdous Haniff, 30, said the unmarked motorbikes have proven effective, adding that foreign police forces, such as those in Australia, employ similar tactics.

Motorcyclist and auditor Chris Yeo, 27, said: "It will make drivers more careful. It's like having plainclothes officers around us."

Mr Bernard Tay, chairman of the Singapore Road Safety Council, said motorists here have been conditioned to look out for TP officers dressed in white and on white motorbikes."If you behave yourself, you have nothing to be scared of," he said.