Additionally, there are issues of connections between different electrical services, particularly connecting intercity lines with sections electrified for commuter traffic, but also between commuter lines built to different standards. This can cause electrification of certain connections to be very expensive simply because of the implications on the sections it is connecting. Many lines have come to be overlaid with multiple electrification standards for different trains to avoid having to replace the existing rolling stock on those lines. Obviously, this requires that the economics of a particular connection must be more compelling and this has prevented complete electrification of many lines. In a few cases, there are diesel trains running along completely electrified routes and this can be due to incompatibility of electrification standards along the route. COUNT 4
QSN1 What is the other issue that comes to sight when using electrification system? ANS1 connections between different electrical services QSN2 Why the commuter lines built to different standards can cause be complicated? ANS2 the implications on the sections it is connecting QSN3 What is the solution many lines came up with in order to avoid replacing present rolling stock? ANS3 to be overlaid with multiple electrification standards QSN4 Why are disel trains  still used on electrified routes? ANS4 due to incompatibility of electrification standards