Quantifying the Value of Robust Public Transport
Menno Yap, Goudappel Coffeng
This paper develops a methodology to quantify the societal costs of disturbances on public transport networks for passengers. This methodology supports the decision-making process regarding the implementation of public transport robustness measures.
Disturbances on public transport networks can have major impacts for passengers, leading to additional travel time, travel costs and reduced comfort. Reducing the frequency and the impact of disturbances, thus improving public transport robustness, is therefore deemed important by passengers, politicians and public transport operators and authorities. Despite the importance of robust public transport networks, current discussions regarding measures to improve robustness only focus on costs of these measures. Until now, it is hardly known what the (societal) costs of disturbances are, and to which extent robustness measures can reduce these costs. This means that currently no trade-off between the costs and (societal) benefits of robustness measures is possible.
To the best of our knowledge, this study is the first which develops a methodology to quantify societal costs of disturbances on public transport networks for passengers. This allows us to calculate the value of robust public transport. We consider robustness from a full passenger perspective in this study. Currently, both in science and practice robustness is usually considered from a single-level network perspective: for each mode and each network level separately. However, we consider robustness from a multi-level perspective, where all public transport network levels and modes are taken into account simultaneously. This means that we take into account the total, integrated public transport network which remains available for passengers after a disturbance occurs on a certain network level.
In the first step of the developed methodology, we designed a stepwise approach to identify the most vulnerable links in the total multi-level public transport network. Therefore, we adjusted existing approaches applied to road networks based on public transport characteristics. For the most vulnerable links, in the second step we expressed the costs of non-robustness in monetary terms by taking into account the frequency, the duration and the impact of disturbances explicitly. Using realization data with information about the frequency and duration of disturbances, and by simulating disturbances on the integrated multi-level network, we can quantify the current costs of non-robustness of these links.
We successfully applied our methodology to the multi-level public transport network of the Randstad Zuidvleugel in the Netherlands. Using this case study we were able to compare robustness of the train, light rail, metro and tram network relative to each other, leading to new insights in this topic. We were also able to design and evaluate robustness measures, by quantifying robustness benefits of these measures.
It is important to realize that the topic of robustness should always be considered in a trade-off with other aspects. Some robustness measures (like the construction of additional switches) can on the one hand reduce the societal costs of a disturbance, if a disturbance occurs, but on the other hand increase the frequency with which disturbances occur. Other measures can reduce the impact of a disturbance for affected passengers, while increasing travel time for other groups of passengers. Some measures might be able to improve robustness substantially on the one hand, but require large investments on the other hand. The result of these trade-offs will be different for different locations in the network and depends on the frequency with which disturbances occur, the impact of disturbances, the number of passengers affected by the disturbance and the extent to which alternative routes are available in the multi-level public transport network. Applying the methodology we developed allows decision-makers to get insight in these trade-offs for each specific location. Also, with our methodology all aspects relevant in such trade-off can be expressed in the same, monetary units. Therefore, our methodology helps to support and rationalize the decision-making process regarding public transport robustness measures.
Association for European Transport