Is having a little extra notice of a traffic jam worth giving up some of your personal privacy?

That’s the question being put to the test by the Missouri Department of Transportation, as it moves forward with a $3 million plan to use drivers’ cell phone signals to track and ease traffic congestion.

The system works by monitoring the signal a cell phone sends to cell towers when it is switched on. As a vehicle with a cell phone in it moves, the strength of the signal and the speed at which it switches from tower to tower can be plotted on a map, thus determining sudden speed decreases.

On a single-car basis, the information doesn’t tell officials much. But if these speed decreases show up in a large number of vehicles in the same area, it’s a pretty good indication of a traffic jam. The information could then be relayed to approaching drivers on electronic highway message signs so they could reroute around the jam.

According to The Associated Press, MoDOT is already in the negotiating process with private contractors to develop the technology, which will cover 5,500 miles of roadways across the state, making the largest project of its kind to date.

MoDOT officials told The AP that user information will remain anonymous, and that the data will only be used to predict traffic patterns.

“There is absolutely no privacy threat whatsoever,” said MoDOT Director Pete Rahn.

However, since the system would use cell phone users’ signals – each of which can be traced back to the phone’s owner – privacy advocates worry about the potential use of the program for the tracking of private citizens.

“Even though it’s anonymous, it’s still ominous,” Daniel Solove, a privacy law professor at George Washington University, told The Kansas City Star. “It troubles me, because it does show this movement toward using a technology to track people.”