Platform screen doors (PSD) are the sliding barrier doors installed at the edges of station platforms in many modern metro stations and occasionally on heavy rail systems. They serve many functions among which are the suicide prevention, optimisation of station energy consumption and safety, particularly by shielding passengers from gaining access to the rail tracks. PSD can prolong dwell time, increase the danger of mantrap and can extend emergency evacuation periods, among others. These pave way for the existence of PSD to have both positive and negative effects on the railway system. This research identified the benefits that could be derived from installing PSD at train stations and the drawbacks associated with its presence, with a view of evaluating the overall effects that the PSD has on the railway system. Upon identification of both factors, a causal loop diagram (CLD) has been developed to enable a pictorial demonstration of the various PSD effects, their systematic interrelations, the polarity of effects, and how they combine to affect the entire railway system. The conclusion reached in the present study was that PSD as a system can have significant impact on many aspects of the railway such as delays, capacity, safety, platform climate control, energy consumption, air quality and so on. But there are no studies that attempt to combine them all into an overall evaluation.