Understanding the Relationship Between Capacity Utilisation and Performance and the Implications for the Pricing of Congested Rail Networks.

There is a growing demand for rail travel in this country which is difficult to satisfy. The result is increased congestion on Britain’s railways. One feature of rail infrastructure congestion is a direct link between capacity utilisation and reactionary delay. The latter is the secondary delay that an already late train causes to a following train.
This thesis re-examines the relationship between capacity utilisation and performance (as expressed by the level of reactionary delay). It compares the effectiveness of the standard measure of capacity utilisation in Britain (the Capacity Utilisation Index or CUI) with amongst others a measure developed in the Netherlands (the Heterogeneity measure or HET) which uses a radically different approach. The analysis presented in this thesis finds that HET which measures how capacity is used through the spacing of trains, is a more effective predictor of the levels of reactionary delay than CUI which simply measures how much capacity is used. In both cases though, an exponential relationship between capacity utilisation and reactionary delay is preferred, reinforcing the work of previous researchers.
In 2002 a congestion charge, called The Capacity Charge, was introduced in Britain. The idea was to encourage the Infrastructure Owner (now known as Network Rail) to accommodate more traffic whilst working with train operators to optimise capacity utilisation on the network. The Capacity Charge is based on the relationship between CUI and reactionary delay. However, this thesis shows that HET based tariffs would charge more for congestion than CUI based tariffs. In addition there is a greater differential between peak and off-peak charges. One conclusion is that CUI undercharges for congestion due to its failure to account for the impact of train ‘bunching’.