The woman suffered critical injuries and died at the scene despite emergency response efforts.
The driver of the Isuzu, a man also aged in his 30s, stopped near the Logan Motorway exit at Tanah Merah and is assisting investigators with inquiries.
The incident triggered significant traffic disruptions, with two additional nose-to-tail crashes occurring shortly afterwards in the same northbound lanes.
The Pacific Motorway was closed for several hours while officers from the Forensic Crash Unit examined the scene. Traffic resumed shortly after 8.30pm.
Police are appealing to anyone who witnessed the incident or captured dashcam footage in the area at the time to come forward.