Jan 04

TRB2017 and related events

Will be attending the Transportation Research Board (TRB) 96th Annual Meeting in Washington DC next week and will also take part in several events that organized in conjunction with TRB.

The following studies which I have been involved in will be presented on TRB this year:

  • Stated-Choice Experiment on Mode Choice in the Era of Free-Floating Carsharing and Shared Autonomous Vehicles (Session 336, Monday 10:15 AM- 12:00 PM Convention Center, 144B)
  • Exact Optimization of Bus Frequency Settings Considering Demand and Trip Time Variations (Session 463, Monday 3:45 PM- 5:30 PM , Convention Center, Hall E)
  • Real-Time Transfer Synchronization of Public Transport Services Using Passenger Data  (Session 463, Monday 3:45 PM- 5:30 PM , Convention Center, Hall E)
  • Constructing Transit Origin-Destination Matrices Using Spatial Clustering (Session 491, Monday 6:00 PM- 7:30 PM, Convention Center, 147A)
  • Investigating Potential Transit Ridership by Fusing Smartcard and Global System for Mobile Communications Data (Session 491, Monday 6:00 PM- 7:30 PM, Convention Center, 147A)
  • Willingness to Pay for Safety Improvements in Passenger Air Travel (Session 678, Tuesday 1:30 PM- 3:15 PM , Convention Center, Hall E)
  • How Do People Cycle in Amsterdam? Estimating Cyclists’ Route Choice determinants Using GPS Data from an Urban Area (Session 878, Wednesday 2:30 PM- 4:00 PM , Convention Center, 102B)

In addition, will take part in:

  • Poster session 250 on New Tools to Inform Transit Management and Decisions (Monday 8:00 AM- 9:45 AM, Convention Center, Hall E) which I will be presiding
  • Lecture session 748 on Ensuring Public Transport Networks are Connected: For Everyone, at All Times (Tuesday 3:45 PM- 5:30 PM, Convention Center, 144A) on which I will be the discussant

In conjunction with the TRB conference I will also participate and present in the following events:

  • Winter General Meeting of the PTV Scientific Advisory Board on which I will present past and on-going research on transit assignment models, Jan 10
  • Shared Mobility from a Public Transport Perspective at the workshop on Shared Mobility at the Netherlands Embassy in Washington, Jan 12
  • Towards Passenger Experience of Service Reliability: Field Implementation and Smartcard Analysis, invited talk at Washington Metropolitan Area Transit Authority, Jan 13

Looking forward to meeting many colleagues on one of these events or elsewhere in what will surely be an intriguing week!

Oct 12

The Tallinn experiment: what happens when a city makes public transport fare-free?

Was interviewed by the Guardian for a piece on the Tallinn experience with free-fare public transport: “According to Cats, free public transport is not the no-brainer everyone might initially think it to be.”  Hope that I was able to provide evidence and nuances into a debate which is often dominated by political views.

Read the full article on the Guardian here.

You can find here the scientific paper which reviews other experiments, reports the evaluation conducted in Tallinn and the key findings.


Jul 02

Prediction for proactive mitigation of bus bunching


A new paper proposes a data driven method to predict Bus Bunching in real-time followed by the selection and deployment of a corrective action based on the assessment of bunching likelihoods. The method was validated using one-year data of 18 real-world bus routes. This combined prediction-control approach can contribute to more proactive bus operations and improved service reliability.


Link to the full paper









Apr 12

Exposing the role of exposure in public transport risk analysis

In the last several years, I have investigated the impact of service disruptions in public transport networks. In a series of network topology and dynamic transit assignment studies, I have looked into indicators of link criticality, measures of impacts on system performance, mitigation value of real-time information provision, identifying strategic links for increased capacity and the robustness value of new links and extension plans.

One common limitation to all of these studies was the lack of information on the probabilities associated with disruptions. This prevented a complete risk analysis and assessing the (e.g. annual) costs and benefits associated with disruptions and mitigation measures.

Together with Menno Yap and Niels van Oort, the frequency and duration of various disruption types on each public transport mode (train, metro, tram and bus) were estimated based on a unique dataset. We also identify which is the primary predictor of each variable to allow researchers and professionals in other contexts to estimate disruption probabilities in the lack of local data.


We propose a method for embedding link exposure into the identification and evaluation of critical links and perform a risk analysis for the multi-modal public transport network of the Rotterdam The Hague Metropolitan Area. By comparing the results with the conventional measures, we demonstrate that disregarding exposure risks prioritizing heavily utilized links instead of those which are actually the weakest.

Click here for the link to the full paper.

Feb 15

What is the robustness value of public transport development plans?

Investments in transport are increasingly motivated by the need to improve its robustness — the capacity to absorb disturbances with a minimal impact on system performance. Nonetheless, there is lack of knowledge on how to assess and quantify the robustness value of new investments as part of strategic planning. This study investigates the robustness of alternative public transport networks by assessing the consequences of link failures on network performance. A full-scan disruption impact analysis is performed and its implications on passenger’s group composition and travel time losses are analysed for a public transport development plan in Stockholm, Sweden. A decision to extend this system substantially with 23 new stations and 35 km of new tracks by 2025 was recently undertaken.

Framtidens spartrafikkarta_söderstaden

The results suggest that as a result of the development plan, the robustness of the case study network will improve in terms of average performance deterioration as well as worst case scenario for all performance indicators. Neglecting abnormal operations in project appraisal can potentially lead to the underestimation of its benefits. Moreover, the critical links in each network are identified and impact disparity is investigated. The analysis method presented in this study can support the consideration of development plan impacts on network robustness in the strategic planning process.

See here the full paper




Jan 07

Two public transport proposals granted

Two public transport projects will be soon launched in the Department of Transport and Planning at TU Delft:

(1) SCRIPTS – on flexible demand-anticipatory services. Granted in the Smart Urban Regions in the Future (SURF) program by NWO [2016-2018; total of 1,800,000€, of which 500,000€ in TU Delft]. ‘Smart Cities’ Responsive Intelligent Public Transport Systems’ will develop advanced models for the optimal design of hybrid public transport systems, involving demand responsive transport services that are flexible in route and schedule and (self-)organized through ICT platforms, and the simulation of their performance, including a series of pilots and showcases.

(2) TRANS-FORM – on real-time transfer and congestion management. Granted in the Co-fund Smart Cities and Communities (ENSCC) call [2016-2018; total of 1,800,000€, of which 315,000€ in TU Delft]. A consortium of universities, industrial partners, public authorities and private operators from Switzerland, Sweden, Spain and the Netherlands, led by TU Delft. ‘Smart Transfers through Unravelling Urban Form and Travel Flow Dynamics’ will develop a multi-level approach for monitoring, mapping, analyzing and managing urban dynamics in relation to interchanging travel flows. Analysis of pedestrian and traveler flows at the hub, urban and regional networks.

Three new PhD positions in the area of public transport modelling will be soon available to work in these projects. Relevant background and skills include simulation modelling, network analysis and optimization.

UPDATE (28-01-2016):

Interested? See the job ad here. Applications are due by February 10.



Oct 17

The more links the better network robustness is?

Investments in public transport projects are increasingly motivated not merely based on travel time savings but also in relation to improvements in service reliability, comfort and robustness. However, there are no standard practices for incorporating the impacts of alternative investments on network robustness.

Together with Erik Jenelius from KTH,  a methodology for assessing the value of new links for public transport network robustness, considering disruptions of other lines and links as well as the new links themselves, was developed. We applied this methodology to a light rail line in Stockholm.

A distinction is made between the value of robustness, defined as the change in welfare during disruption compared to the baseline network, and the value of redundancy, defined as the change in welfare losses due to disruption. Topological studies concluded that redundancy is an important feature for network robustness. Interestingly, we found that In some cases, the new line results with seemingly paradoxical effects as it leads to greater disruption costs.

Check the full paper here


Sep 08

What can passenger counts tell us about urban form and dyanmics?

Apparently quite some interesting insights!


Using a simple clustering method, transport data such as passenger counts can be used to identify the main activity centers. Activity clusters are then classified based on their time-dependent flow profile including magnitude, directness and the distribution of incoming and outgoing flows. It is postulated that urban structure and the spatial distribution of activities are manifested through time-dependent flow profile because activity centers with distinguished functions will yield distinctive travel patterns throughout the day. The method developed in this paper is directly transferable to different data sources, networks and scales.

The method can be used by policy makers and planners to provide insights on the discrepancy between the planning policy and the prevailing urban structure. This technique might be most valuable for anlayzing urban forms in mega-cities in emerging economies which undergo rapid changes.

Together with Qian Wang and Yu Zhao, we applied this method to the Stockholm metropolitan area. Stockholm is famous for its long-term monocentric planning with a dominant central core. Since the turn of the century there has been a noticeable shift towards developing sub-centres but to what extent has it been realized insofar?

See the results of our analysis in the full paper – available here. 

Figure 9 Poly



Aug 03


INSTR2015 – 6th International Symposium on Transportation Network Reliability – the Value of Reliability, Robustness and Resilience, took place yesterday and today in Nara, Japan. First time that I take part in what seems to be a very relevant conference for my line of research concerning the reliability and vulnerability of public transport systems.

Here you can find my conference contributions concerning:

(1) Multi-crtieria evaluation of the resilience value of public transport investment plans based on a full-scan approach with the Stockholm public transport development plan as a case study (click for paper: instr2015_Cats_resilience_value)

(2) Investigating the role of exposure in public transport network vulnerability. A work that was preformed together with Menno Yap and Niels van Oort based on estimating large disruption data from the Netherlands and analyzing the impacts of accounting for exposure on the identification and evaluation of link criticality. (click for paper: instr2015_EXPOSURE). Below: Menno presenting on INSTR.

2015-08-03 15.21.37

(3) Analyzing the impact of partial (unlike complete) failures. Together with Erik Jenelius, we studied the relation between the extent of capacity reduction at the line level and its consequences on societal costs by performing a full network scan for the Stockholm network (click for paper: Beyond a complete failure INSTR) Below: Erik presenting on INSTR.

2015-08-03 14.05.57

Each of these studies deployed a distinctly different methodologies – network topology analysis (while accounting for travel impedance and demand), static assignment model and a dynamic agent-based transit assignment model, respectively.

Below: Still astonished by the Japanese public transport system!


May 31

Planning for the unplanned – where shall we allocate reserve capacity?

In the field of network vulnerability and resilience, there is growing evident that network redundancy is a key determinant of network capability to withstand shocks. However, introducing redundancy to rapid public transport networks is very expensive and it is thus important to identify the network elements that will benefit most network performance in case of disruption.

It is crucial to invest in network redundancy without making redundant investments!

Den Haag CS 2 - smaller

Together with my colleague from KTH, Erik Jenelius, we propose and demonstrate in a new paper a methodology for evaluating the effectiveness of a strategic increase in capacity on alternative public transport network links to mitigate the impact of unexpected network disruptions. For a given disruption scenario, a set of links is first identified as candidates for capacity enhancement based on (i) their initial saturation levels in terms of volume to capacity ratios, and (ii) the overloading in terms of increased saturation that occurs due to the disruption. Second, the effect of capacity increase is evaluated for each candidate link by comparing the disruption impacts with and without increased capacity. Based on the evaluation the most effective of the mitigation actions can be identified.

We applied the methodology to  a case study of the high frequency public transport network of Stockholm. To evaluate the public transport system performance under varying conditions, BusMezzo, a dynamic public transport operations and assignment model was used.

The method presented in this paper could support policy makers and operators in prioritizing measures to increase network robustness by improving system capacity to absorb unplanned disruptions.


Click here for the full paper.


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