Chicago Transit Authority riders soon will know when the next train, really, is coming. CTA President Ron Huberman says more than 1,300 extra-large digital screens are going up in rail stations and at subway entrances to give riders real-time information about how many minutes away the next train is. Right now it's a stand-and-wait game. The new screens are part of a deal the CTA has with a company to sell digital advertising. The CTA estimates it will collect about $100 million in revenue over the life of the 10-year deal. Huberman says the digital screens also will be used to alert riders to delays and communicate with people in a city emergency. Huberman says the first screens should be up in about four months.