Newark Liberty International Airport is warning drivers to take their keys out of the ignition when exiting their vehicles near the arrival and departure doors. According to a law enforcement source, the move was prompted by an unfortunate pattern of criminal activity at the airport.

Newark Liberty International Airport (Townsquare Media)

Victims of the supposed crime are leaving their vehicles, engine on, to greet loved ones or grab luggage, and that small window of time is just enough for a thief to jump in the front seat and drive off.

According to a source close to the issue, reports of stolen vehicles seem to pop up "every few months, right in front of the terminals."

Digital signs outside of the airport have been programmed to inform drivers of the proper way to leave their vehicles unattended.

A spokesman for the Port Authority of New York & New Jersey, which handles patrols at the airport, said the message has nothing to do with recent events, and it's a "continuing part of safety and security awareness."

But Chris Dinadio, a driver with Ross Limo in Neptune, said he's been traveling to the airport for 12 years and hasn't seen these warnings until very recently.

He was told by a Port Authority officer that the signs are meant to prevent theft and "rolling vehicles." He has personally seen many drivers leave their cars without first shifting to park.

Dinadio said he wouldn't be surprised if car theft is a legitimate problem at Newark Liberty because there are plenty of people "on the various levels of the road" that have no business being at an airport.

"The Port Authority police does a good job of shooing them away, but they're still there," he said.

Nick Irons, a criminal justice professor at the County College of Morris, insisted airports are a prime target for bad guys. Police aren't going to stop every vehicle that exits, Irons said, so it's up to the drivers and passengers to reduce the opportunity for crime.

"Take your keys out; lock the car," Irons said. "It's a habit that you have to get in to."

In late 2012, the airport dealt with a string of luxury vehicle thefts over a period of several weeks.

Dr. Paul Boxer, part of Rutgers' School of Criminal Justice, said crimes that occur right in front of crowds and several officers - as would be the case outside an airport terminal - require "a very high degree of narcissism and inflated self-esteem, two traits that can be common in criminal offenders."

"We also know that folks who engage in criminal offending are more likely to crave risk and seek out excitement," Boxer said. "And it sounds like these crimes fit that bill."