Fourteen people have been killed on Tonga's roads this year, according to police records up to Wednesday, a big increase on last year.
The road toll tally for all of 2021 was six.
The latest death on the road occurred on Saturday morning near the capital Nuku'alofa.
Police said four females were on their way home when the driver fell asleep at the wheel, causing the vehicle to swerve and hit an electric pole.
Police later received reports from Vaiola Hospital that a 51-year-old passenger died on Sunday from her injuries, while the 41-year-old driver remains in a critical condition.
Tonga Police will reinforce its road safety services throughout the holiday season including deploying alcohol breath-testing teams.
The force is urging road users to take their responsibility on public roads seriously.