Police have launched a month-long campaign in Merseyside reminding motorists and passengers to wear seatbelts.
Officers carried out a similar scheme in April this year.
More than 2,000 vehicles were stopped where drivers or passengers were not wearing seatbelts.
Merseyside Police said it will also target drivers who use their mobile phones behind the wheel, with more than 600 motorists stopped last time.
'Terrible injury'
The force has highlighted research which it said has shown that in a 30mph collision the passenger in the back seat is thrown forwards with a force of up to 60 times their own body weight.
It is estimated that up to 15 front seat occupants are killed by an unbelted rear passenger each year in the UK.
Traffic Insp Dave Bell, of Merseyside Police, said: "During a collision an unrestrained passenger risks terrible injury from potential impact with the windscreen, dashboard and other passengers.
"During this campaign we will also be clamping down on those people still willing to drive when on a mobile telephone."