Trains run every fifteen minutes in basic midday service.
The Yellow Line is almost unique among North American rapid-transit lines in that it uses a hybrid power system. The eastern half of the line uses a third rail, and the western half uses overhead catenary. This mode of operation came about because of the historical background of the line. Like most interurbans, the North Shore line used overhead catenary on the suburban and rural portions of its route, but had to use third rail to reach the Loop. When the North Shore line was abandoned in 1963, the Chicago Transit Authority took over the portion between Dempster and Howard and converted it into a rapid-transit line.