Some trains on the New Canaan Branch, including those stopping at the Glenbrook, Springdale and Talmadge Hill stations, will be replaced by buses on Friday nights and on weekends from July 31 to Aug. 23, the Metropolitan Transportation Authority announced.Trains for normal commuting times will not be affected, according to the announcement on the MTA website. The substitutions of bus service will take place for trains leaving the New Canaan station at 11:15 p.m. on Fridays, starting July 31 (this Friday), and for all weekend trains (leaving the station between 6:15 a.m. and 11:15 p.m.). Buses will leave 15 to 20 minutes earlier than the scheduled trains. Trains arriving at the New Canaan station 0n Fridays from 11:15 p.m. to 1:17 a.m. (and at the Talmadge Hill Railroad Station between 11:09 to 1:11 a.m.) will also be replaced by buses.