Mass rapid transit plays an important role in providing a sustainable form of transport in densely populated areas. Public transport operators worldwide are experiencing an increase in popularity of their network and are experiencing ridership growth on their metro networks. To accommodate ridership growth, many transport operators are tasked with increasing the capacity of their metro network. While widening or elongating trains can be a too costly alternative to increase capacity, increasing frequencies can be interesting. However, the offered level of service might be jeopardised. Increasing frequencies might lead to higher delays and irregular services, resulting in a lower level of service than when lower frequencies are maintained. With the use of microscopic simulation tool OpenTrack, this research has given a quantitative analysis of the effects of increasing frequencies on timetable reliability. For a case study of the Rotterdam metro network, this research has developed four growth scenarios in which the frequencies are increased. It has found that a timetable with trunk section intervals up to 150 seconds still yield reliable services, however lower intervals yield more unreliable services. The implementation of moving block signaling can reduce delays of 40-50 percent, depending on the timetable. However, for irregularity, removing the driver from the front of the train, creating more buffer time at terminal stations, yields higher improvements than moving block does. This research has shown that moving block and metro automation can enable reliable services for timetables with very high frequencies. However, the operator is still faced with a choice to either strive for punctual trains, or to strive for regular trains.