Research conclusions: During the innovation of existing line for enhancing traffic capacity, the lengths of partial tracks can be prolonged under the condition of difficultly conducting innovation and other special conditions by setting the signal into double departure way. Application of a special signal structure with additional blue light indication of departure signal and adopting a special signal indication and mute setting way can basically satisfy the traffic requirement and reduce the modification of the existing circuits as much as possible. Addition of train terminal circuit and modification of signal lighting circuit can guarantee the safety of train route and shunting route.