Rafal Kucharski Lab

I research complex social systems: urban mobility. Congested, urban multimodal networks used by millions of agents to reach their destinations and leaving huge sets of mobility traces ready to be applied for modelling, optimization, understanding and control.

I now focus on ride-pooling, i.e. Uber-like systems where two or more travellers share a single vehicle. This is highly challenging combinatorial optimization problem, to which I contributed with the ExMAS algorithm. This, the first user-centric demand driven exact ride-poling algorithm, rooted a long and rewarding stream of contributions in e.g.: Game Theory, Virus Spreading, Network Science, Transit Network Desing Problem and growing.

Currently, as an Assistant Professor in the Faculty of Mathematics and Computer Science of Jagiellonian University in Krakow (Poland) I am part of the Group of Machine Learning Research GMUM. I run the NCN Opus Grant on Shared Mobility in the pandemic times and run a team to research complex social systems of urban mobility within the DigiWorld scheme. We are now a team of two PhDs, two PostDocs and me.

Before, I worked (2019-2021) with Oded Cats at TU Delft in his ERC Starting Grant Critical MaaS. I model two-sided mobility platforms, specifcally focusing on ride-pooling (ExMAS) and agent-based simulator for Uber-like systems (MaaSSim). I did PhD at Cracow University of Technology with excellent goup of prof. Andrzej Szarata and working closely with Guido Gentile from La Sapienza on non-equilibrium dynamic traffic assignment. In the interdisciplinary field of urban mobility I did research which can be classified as:

model estimation, optimization, system control, network design;
agent-based simulation, game-theory, network science, stochastic simulation, epidemic modelling;
machine learning, spatial analysis, big data analysis, pattern recognition, unsupervised learning;
behavioural modelling, economic discrete choice models, policy, sustainability.

Outside of academia I was:

Data Scientist at NorthGravity developing AWS-based protfolio or real-time production ready ML solutions
R&D Developer at PTV SISTeMA implementing algorithms into PTV Optima real-time traffic forecasting models.
Transport Modeller at Department of Transportation Systems using travel-diaries to estimate demand models and create strategic planning tools, e.g. for Warsaw and Kraków

drawing

Teaching materials

I run the seminar on Complex Social Systems (transport is one of them) at Jagiellonian University - materials and papers are on my github

news

Sep 9, 2022	We launched collaboration on Network-Science with the group of prof. Rob Kooij to exploit how networks shape the ride-pooling problems. Today I gave a seminar for his group in Delft.
Aug 5, 2022	👏 1st Aug is a relief day for all transport-people, so it was for us, we can be happy with out TRB submissions, kudos to all👏: 🧨 Farnoud Ghasemi made an intiguing ABM simulations of Uber rise and fall: https://arxiv.org/abs/2208.02496 🧨 Usman Akhtar explored when and why the ride-pooling calculations explode: https://arxiv.org/abs/2208.02504 moreover: 🧨 Olha Shulika is closing up her Post-Pandemic Ride Pooling Review and 🧨 Michal Bujak lately got accepted for Complex Networks conference with his probabilistic ride-pooling: https://arxiv.org/abs/2206.12259 That is not a bad outcome for the first 12 months of our group - let’s take some well-deserved rest: 🏝⛱🏝⛱🏝⛱🏝⛱
Jun 15, 2022	Our pre-print is out. Typically it is too early to announce, but this is super-exciting. We managed to push the limits of pooling to the edge: 14 co-travellers in an attractive hyper-pooled rides (turbo version of our ExMAS)
Jun 8, 2022	Our flagship software is out and published. Along with a documented repository, the MaaSSim community have now the deeper and more formal documentation in PLOS One - hope it can help the community grow.
Jun 6, 2022	I presented the Ride-Pooling problem at our flagship national conference Modelling 2022 at Cracow University of Technology. Good opportunity to introduce my team and research problems to exceptional practitioners involved in most challenging infrastructure projects in the country. slides
Jun 6, 2022	After 2+ years, finally in person meeting with the community @ heart conference in Leuven. Six contributions from our side (Arkadiusz Drabicki, Michal Bujak, Marko Maricic, Peyman Ashkrof, Arjan de Ruijter and Farnoud Ghasemi presented results of our joint work). Plus a great keynote by prof. Oded Cats, summarizing roughly all on which our lab is founded, including ExMAS and MaaSSim.

selected publications

PLOS

Simulating two-sided mobility platforms with MaaSSim

Kucharski, Rafał, and Cats, Oded

PLoS ONE 2022

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Two-sided mobility platforms, such as Uber and Lyft, widely emerged in the urban mobility landscape. Distributed supply of individual drivers, matched with travellers via intermediate platform yields a new class of phenomena not present in urban mobility before. Such disruptive changes to transportation systems call for a simulation framework where researchers from various and across disciplines may introduce models aimed at representing the complex dynamics of platform-driven urban mobility. In this work, we present MaaSSim, a lightweight agent-based simulator reproducing the transport system used by two kinds of agents: (i) travellers, requesting to travel from their origin to destination at a given time, and (ii) drivers supplying their travel needs by offering them rides. An intermediate agent, the platform, matches demand with supply. Agents are individual decision-makers. Specifically, travellers may decide which mode they use or reject an incoming offer; drivers may opt-out from the system or reject incoming requests. All of the above behaviours are modelled through user-defined modules, allowing to represent agents’ taste variations (heterogeneity), their previous experiences (learning) and available information (system control). MaaSSim is a flexible open-source python library capable of realistically reproducing complex interactions between agents of a two-sided mobility platform. MaaSSim is available from a public repository, along with a set of tutorials and reproducible use-case scenarios, as demonstrated with a series of illustrative examples and a comprehensive case study.
PLOS

Beyond the dichotomy: How ride-hailing competes with and complements public transport

Cats, Oded, Kucharski, Rafal, Danda, Santosh Rao, and Yap, Menno

Plos one 2022

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Since ride-hailing has become an important travel alternative in many cities worldwide, a fervent debate is underway on whether it competes with or complements public transport services. We use Uber trip data in six cities in the United States and Europe to identify the most attractive public transport alternative for each ride. We then address the following questions: (i) How does ride-hailing travel time and cost compare to the fastest public transport alternative? (ii) What proportion of ride-hailing trips do not have a viable public transport alternative? (iii) How does ride-hailing change overall service accessibility? (iv) What is the relation between demand share and relative competition between the two alternatives? Our findings suggest that the dichotomy—competing with or complementing—is false. Though the vast majority of ride-hailing trips have a viable public transport alternative, between 20% and 40% of them have no viable public transport alternative. The increased service accessibility attributed to the inclusion of ride-hailing is greater in our US cities than in their European counterparts. Demand split is directly related to the relative competitiveness of travel times i.e. when public transport travel times are competitive ride-hailing demand share is low and vice-versa.
CIiT

Using city-bike stopovers to reveal spatial patterns of urban attractiveness

Banet, Krystian, Naumov, Vitalii, and Kucharski, Rafał

Current Issues in Tourism 2022

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We demonstrate how digital traces of city-bike trips may become useful to identify urban space attractiveness. We exploit their unique feature – stopovers: short, non-traffic-related stops made by cyclists during their trips. As we demonstrate with the case study of Kraków (Poland), when applied to a big dataset, meaningful patterns appear, with hotspots (places with long and frequent stopovers) identified at both the top tourist and leisure attractions as well as emerging new places. We propose a generic method, applicable to any spatiotemporal city-bike traces, providing results meaningful to understand the general urban space attractiveness and its dynamics. With the proposed filtering (to mitigate a selection bias) and empirical cross-validation (to rule-out false-positive classifications) results effectively reveal spatial patterns of urban attractiveness. Valuable for decision-makers and analysts to enhance understanding of urban space consumption patterns by tourists and residents.
SciRep

Modelling virus spreading in ride-pooling networks

Kucharski, Rafał, Cats, Oded, and Sienkiewicz, Julian

Scientific Reports 2021

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Urban mobility needs alternative sustainable travel modes to keep our pandemic cities in motion. Ride-pooling, where a single vehicle is shared by more than one traveller, is not only appealing for mobility platforms and their travellers, but also for promoting the sustainability of urban mobility systems. Yet, the potential of ride-pooling rides to serve as a safe and effective alternative given the personal and public health risks considerations associated with the COVID-19 pandemic is hitherto unknown. To answer this, we combine epidemiological and behavioural shareability models to examine spreading among ride-pooling travellers, with an application for Amsterdam. Findings are at first sight devastating, with only few initially infected travellers needed to spread the virus to hundreds of ride-pooling users. Without intervention, ride-pooling system may substantially contribute to virus spreading. Notwithstanding, we identify an effective control measure allowing to halt the spreading before the outbreaks (at 50 instead of 800 infections) without sacrificing the efficiency achieved by pooling. Fixed matches among co-travellers disconnect the otherwise dense contact network, encapsulating the virus in small communities and preventing the outbreaks.
TR:B

Exact matching of attractive shared rides (ExMAS) for system-wide strategic evaluations

Kucharski, Rafał, and Cats, Oded

Transportation Research Part B: Methodological 2020

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The premise of ride-sharing is that service providers can offer a discount, so that travellers are compensated for prolonged travel times and induced discomfort, while still increasing their revenues. While recently proposed real-time solutions support online operations, algorithms to perform strategic system-wide evaluations are crucially needed. We propose an exact, replicable and demand-, rather than supply-driven algorithm for matching trips into shared rides. We leverage on delimiting our search for attractive shared rides only, which, coupled with a directed shareability multi-graph representation and efficient graph searches with predetermined node sequence, narrows the (otherwise exploding) search-space effectively enough to derive an exact solution. The proposed utility-based formulation paves the way for model integration in travel demand models, allowing for a cross-scenario sensitivity analysis, including pricing strategies and regulation policies. We apply the proposed algorithm in a series of experiments for the case of Amsterdam, where we perform a system-wide analysis of the ride-sharing performance in terms of both algorithm computations of shareability under alternative demand, network and service settings as well as behavioural parameters. In the case of Amsterdam, 3000 travellers offered a 30% discount form 1900 rides achieving an average occupancy of 1.67 and yielding a 30% vehicle-hours reduction at the cost of halving service provider revenues and a 17% increase in passenger-hours. Benchmarking against time-window constrained approaches reveals that our algorithm reduces the search-space more effectively, while yielding solutions that are substantially more attractive for travellers.
TR:B

Simulation of rerouting phenomena in Dynamic Traffic Assignment with the Information Comply Model

Kucharski, Rafał, and Gentile, Guido

Transportation Research Part B: Methodological 2019

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We present the Information Comply Model (ICM) which extends the framework for macroscopic within-day DTA proposed by Gentile (2016) to represent the rerouting of drivers wrt a single traffic event. Rerouting is reproduced as a two-stage process: first, drivers become aware about the event and its consequences on traffic; second, drivers may decide to change path. At each arc, unaware drivers have a probability of being informed by multiple ATIS sources (radio, VMS, mobile apps), which depends not only on devise penetration rates, but also on users space and time coordinates wrt the position and interval of the event. At each node, aware drivers, who are somehow reluctant to change, may finally modify their path based on a random rerouting utility, which is composed of expected gains and avoided losses. ICM is thus capable of representing the evolution of rerouting phenomena in time and space when the information about a traffic event and its consequences on congestion spread among drivers and onto the network. This way, ICM extends the concept of dynamic user equilibrium to a case of imperfect information related to availability and awareness rather than to individual perception, as well as to a case of bounded rationality with prudent drivers. Besides the model architecture and specification, this paper provides a workable methodology which can be applied both off-line for transport planning and in real-time for traffic management on large size networks.
EJOR

How to split the costs and charge the travellers sharing a ride? Aligning system’s optimum with users’ equilibrium

Fielbaum, Andres, Kucharski, Rafał, Cats, Oded, and Alonso-Mora, Javier

European Journal of Operational Research 2021

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Emerging on-demand sharing alternatives, in which one resource is utilised simultaneously by a circumstantial group of users, entail several challenges regarding how to coordinate such users. A very relevant case refers to how to form groups in a mobility system that offers shared rides, and how to split the costs within the travellers of a group. These are non-trivial tasks, as two objectives conflict: 1) minimising the total costs of the system, and 2) finding an equilibrium where each user is content with her assignment. Aligning both objectives is challenging, as users are not aware of the externalities induced to the rest. In this paper, we propose protocols to share the costs within a ride so that optimal solutions can also constitute equilibria. To do this, we model the situation as a non-cooperative game, which can be seen as a game-version of the well-known set cover problem. We show that the traditional notions of equilibrium in game theory (Nash and Strong) are not useful here, and prove that determining whether a Strong Equilibrium exists is an NP-Complete problem, by reducing it to the k-Exact-Cover problem. Hence, we propose three alternative equilibrium notions (stronger than Nash and weaker than Strong), depending on how users can coordinate. For each of these equilibrium notions, we propose a (possibly overcharging) cost-sharing protocol that yields the optimal solutions equilibria. Simulations for Amsterdam reveal that our protocols can achieve stable solutions that are close to the optimum, and that having a central coordinator can have a large impact.