A 2007 study by IDOT estimated the cost could go as high as $6.6 million for Metra's 550 miles of track.
However, some transportation experts point out the price for that technology is getting cheaper now.
On another matter, Metra is increasing the maximum number of bikes that can be put on each train car from 3 to 5, as long as there is room.
The new higher limit is under a one-year trial period. Bikes on trains still are not allowed during rush hour times.