SINGAPORE, May 25 – Singapore’s Immigration and Checkpoints Authority (ICA) said it will carry out a safety review after a car and bus collided at Woodlands Checkpoint early yesterday morning in an accident it said "should not have happened”.

The crash occurred at 5.28am when a departing Singapore-registered car collided with an arriving Malaysia-registered bus on the Causeway, with ICA confirming that the contraflow operation had been activated before safety barriers were set up.

"This accident should not have happened. ICA is treating it very seriously, and we are assisting the Traffic Police who are investigating the accident,” CNA cited the agency saying.

Singapore police said the car driver, a 48-year-old man, and his three passengers aged between 14 and 78 were taken conscious to hospital, while no bus passengers were injured and the bus driver declined medical attention.

All lanes for departing traffic were reopened by 9.09am, almost four hours after the collision, according to a Facebook post by ICA.

The agency explained that contraflow traffic management is used during peak hours to ease congestion, including converting the departure lane for heavy vehicles into an arrival lane to allow incoming trucks to move through more smoothly.

It added that when car traffic out of Singapore surges, part of the departure cargo zone might be used to clear outbound vehicles and reduce tailbacks along the Bukit Timah Expressway.

As part of standard safety procedures, barriers are supposed to be placed to divert outbound car traffic away from lanes temporarily used for incoming heavy vehicles.

ICA has since imposed a safety pause by halting contraflow operations at both the Woodlands and Tuas checkpoints over the weekend.

"We will comprehensively review our safety measures before restarting the contraflow operations. Motorists can expect some delays in the interim and we apologise for any inconvenience,” it said.