CHICAGO (CBS) — New security measures have been announced to improve safety on CTA trains, under a federal counter-terrorism initiative. 
 
 CBS 2’s Susanna Song reports, starting Nov. 3, if you ride the “L,” prepare to be asked to hand your bags, purses, or suitcases to a Chicago police officer to be screened for explosives at some stations. 
 
 Passengers will be selected at random before passing through turnstiles at CTA train stations. 
 
 Police officers with a mobile explosive screening team will swab bags and place the sample in a machine to check for explosive compounds. Bags will not be opened. The test takes only about 30 seconds. 
 
 “We know the fears and the possibilities. It’s going to take 20 to 30 seconds of someone’s time. While we know our commuters’ time is precious, we think their safety is probably priceless,” Chicago Police Public Transportation Cmdr. Nancy Lipman said. ||||| Riders and a public transit expert expressed skepticism about a Chicago police plan to stop some rush-hour riders before they pass through rail station turnstiles to screen their bags for explosives. 
 
 There is "no known terrorist threat" that prompted the new procedure slated to begin the week of Nov. 3, Nancy Lipman, Chicago police commander for public transportation, said Friday at a news conference announcing the initiative. 
 
 Chicago police spokesman Marty Maloney says the security measure is a "proactive, protective measure." 
 
 "We know that surface transportation has been targeted in other places in the past [Madrid, New York, London, Russia] and want to take whatever precautions possible," Maloney told RedEye. 
 
 Amtrak and the New York City and Washington transit stations employ a similar screening measure, Lipman said. While officials won't disclose the pricetag for the CTA security initiative, it is being fully funded with part of a $3.5 million federal anti-terrorism grant. 
 
 Some CTA riders Friday said they were concerned that passengers stopped for bag checks could opt out of the procedure. Joseph Schwieterman, a DePaul professor specializing in transportation issues, said it's difficult for mass transit systems to provide airport-level security. 
 
 "Unfortunately, it's needle in a haystack trying to identify vulnerabilities in mass transit systems," Schwieterman said. "We have hundreds and hundreds of access points to our stations." 
 
 Chicago police say they will randomly select one rail station each day to set up the screening table outside the rail turnstiles during rush hour. Lipman said most of the stations will be downtown but other stops will be included as well. 
 
 A team of four to five officers will man the table, which will have two explosives testing machines. 
 
 Police will approach riders, whom they have randomly selected by picking a random number that morning, Lipman said. 
 
 For example, if police pick the number 10, they will ask the 10th person who enters the station, then the 20th and so on, Lipman said. 
 
 Police say they will swab the outside of the bags but will not open them during the test. 
 
 Cloth rubbed on the bag is inserted into the testing machine. At that point, a positive or negative result registers on the machine's screen. 
 
 Riders who pass the test are free to enter the turnstiles. Officers will ask to inspect the bags of riders who fail the test. Police say the machines are testing the presence of explosives, not drugs. 
 
 The whole process should take "less than a minute," Lipman said during the Friday press conference at the Clinton stop on the Green and Pink lines. "We expect it to have no impact on a customer's commute time." 
 
 Riders who refuse to have their bag swabbed won't be allowed to get on the train—in fact they'll be ordered to leave the station. But they can head to another station to board the train, police said. 
 
 Or, if police suspect the rider is involved in "further suspicious activity, and if we determine that probable cause exists to stop him/her for questioning, we might do so," Maloney said. Riders who say no to the swabbing but try to enter that station's turnstiles face arrest, police say. 
 
 The screenings at stations will occur "several times a week," police said. 
 
 Michael Garcia, 30, said he typically carries a backpack when he rides CTA trains from Skokie to the Midway Airport Orange Line every day for work. Garcia said he would agree to testing if he is asked but questioned whether there could be a better process. 
 
 "If they swab one random person's bag, what about the next person who might have something?" Garcia asked. "I think it's just a waste of money and time." 
 
 CTA spokesman Brian Steele said the screenings will be performed during rush hour so riders won't have to worry about missing their train if they undergo the test because of continual train service. 
 
 More than 229 million CTA rail rides were taken in 2013. The CTA has more than 140 rail stations. 
 
 Tim Looney, who typically rides the Brown Line to the Clark/Lake Loop station for work, said he doesn't believe this program will be successful because riders can opt out of the screenings. 
 
 "It seems like the way they're announcing it, they're letting us know you can just leave the station and go to the next station if you had a bomb in your bag. To me, I just don't imagine too many people would get caught," said Looney, of Andersonville.
– Chicago police will screen the bags of passengers getting on the city's CTA trains in what the department calls a "proactive, protective measure," the Chicago Tribune reports. "We know that surface transportation has been targeted in other places in the past"—places like Madrid and New York—and police "want to take whatever precautions possible," says a spokesman. A few days a week, passengers at a single station will be randomly selected to have their bags swabbed, but not opened, in a check for explosives. If passengers refuse the test, they'll be required to leave the station, but they can get on the train elsewhere—unless police have "probable cause" to question them, the spokesman says. If a passenger fails the swab test, police will ask to look in his or her bag. The program, funded using a portion of a federal anti-terror grant, has some riders questioning its usefulness. "If they swab one random person's bag, what about the next person who might have something?" asks one passenger. "I think it's just a waste of money and time." As for time, a police officer says it will take "20 to 30 seconds" to do a check, CBS 2 reports. "While we know our commuters’ time is precious, we think their safety is probably priceless."