The novel crime prevention initiative is aimed at cutting down on the amount of property taken from cars, simply because drivers leave property on display.
The Vulnerable Vehicle initiative involves police officers to visiting car crime hot-spots and noting the registrations of cars with valuable items left on view inside.
Letters are then sent to the owners telling them their vehicles were vulnerable to theft.
Sgt Helen Parkinson who is overseeing the operation said: "It's a simple, but effective idea that makes it clear to the owner that we've noticed that the car was vulnerable and a prime target for car crime.
"On one night alone we put notices on cars that had items on show including a laptop case and a sat-nav system. Another car had an open window.
"The aim is for people to learn from this in future when they leave their car unattended.
"Car crime is at its lowest levels for a number of years but people should not get complacent. Most vehicle crime is opportunistic and can be easily prevented.
"Making sure your vehicle is locked – and there is nothing on display before you leave it – will significantly reduce the chances of it being broken into."