G. Homem de Almeida Correia
19 records found
1
Transfer Towards European Train Travel
A stated choice experiment into the effect of train transfer attributes on long-distance leisure travel choice behaviour
E-commerce is rapidly growing and is expected to encompass a quarter of all global sales by 2025. This growth pressures e-commerce warehouses to enhance efficiency. A promising innovation is the Robotic Mobile Fulfilment System (RMFS), which optimises warehou ...
E-commerce is rapidly growing and is expected to encompass a quarter of all global sales by 2025. This growth pressures e-commerce warehouses to enhance efficiency. A promising innovation is the Robotic Mobile Fulfilment System (RMFS), which optimises warehouse operations by using robots to manage storage and retrieval tasks, thus significantly improving productivity, speed and accuracy. This research focuses on how inventory allocation (slotting) decisions with RMFS can optimise operational performance. In particular, how the slotting decision of Stock Keeping Unit (SKU) distribution across movable storage racks (pods) based on SKU turnover can maximise order throughput rates and optimise operational performance. The research question guiding this study is: What is the optimal demand-based slotting decision to maximise the order throughput rate in a Robotic Mobile Fulfilment System? This question aims to provide insights into how different slotting configurations impact the efficiency and performance of ecommerce warehouses. The research approach is twofold. A general analysis is conducted to understand the impact of turnover-based slotting decisions using synthesised demand profiles derived from literature. This is followed by a detailed case study for Gall&Gall using demand profiles derived from real-world data to find specific optimal slotting configurations and validate the synthesised demand results. The methodology involves three main steps: determining demand configurations, generating slotting configurations with a mathematical model, and simulating these configurations to evaluate performance. Each demand configuration results in multiple slotting configurations, which are evaluated with the simulation to gain insights into the effect of slotting decisions on performance. The different demand profiles consist of total SKU quantity, total item quantity, and SKU classification into three classes (A, B and C) based on their item turnover. The different slotting configurations consist of different distributions of the three classes over the pods. These slotting configurations are obtained with a mathematical model that prioritises class distribution based on given weights. The simulation tool RawSim-O assesses the slotting configurations on key performance indicators such as total order throughput rate and the number of items picked from a pod in one go (pile-on). Key findings provide that pile-on and travel distance significantly affect the order throughput rate, with performance variations of up to 40 orders handled in 30 minutes. High performance often arises with configurations aiming for an equal number of items per pod across classes and maximising the number of pods for SKUs in class A. While synthetic demand profiles show high performance with class A distributed over the maximum number of pods or equal items per pod for all classes, the Gall&Gall demand profiles perform better with class B distributed over slightly more pods, indicating variability in optimal slotting approaches based on specific demand characteristics. Overall, turnover-based slotting decisions significantly impact order throughput rates in RMFS, and tailoring slotting configurations to specific demand characteristics is crucial for optimal operational efficiency. In addition to general slotting insights, this research developed a method that allows warehouses to input their specific demand characteristics and receive insights on optimal slotting approaches. Furthermore, the method enables the readjustment of warehouse-specific details, such as a warehouse’s unique layout, for extra applicability and realism, and allows the integration of additional decision problems, such as order batching and routing, to broaden the method’s scope. This supports warehouses with the design of a tailored, robust and effective slotting strategy for operational performance improvement
Setting the Price for Carsharing
A Cost-Benefit Analysis of Equitable Carsharing in the Car-free Neighbourhood of Merwede
An integrated approach to implementing opportunity charging for electric buses
A case study of Rotterdam
Crowdshipping as a delivery solution for outlier parcels
A case study in The Hague
Therefore, this study aims to investigate the transport impacts of crowdshipping service for outlier parcels, which are defined as the parcels with high environmental impacts. A case study is conducted in The Hague. First, the parcel carbon footprint is calculated to segregate the outlier parcels. Then, a public transport-based crowdshipping delivery scenario is proposed, with parcel lockers at train stations as the transfer points and train travellers as the potential occasional couriers. The simulation results show that outsourcing the outlier parcels to crowdshipping service is beneficial to the transport system and prioritising outlier parcels of logistics service providers with low market shares can achieve more savings in transport and higher service efficiency.
This study considers three refrigeration methods for controlling the pressure level at refuelling stations. These are nitrogen cooling, offload cooling and logistic trailer cooling. The identified key performance indicators that are used to evaluate the develop planning method are: Total Costs, Total Transportation Costs, Total Nitrogen Cooling Costs and Cost per Kilogram. Furthermore, the key constraints and variables for the integrated control of the LNG logistics are identified.
The planning methodology was developed through three steps. First a Full Mixed-Integer Linear Programming (MILP) model was developed. Second, the Full-MILP model was refined to a Simplified MILP model. This Simplified MILP model was improved with the rolling horizon approach and a pre-solve process. The rolling horizon approach divided the planning horizon into smaller manageable time blocks. The pre-solve process identified the critical stations for each day to reduce the number of nodes in the network.
The proposed planning methodology was experimented in the case study that involved a network of 19 refuelling stations in the Netherlands and Belgium. The sensitivity analysis indicated that the model was sensitive to the vehicle capacity. Therefore, the pre-solve process was extended with determining the supply of LNG. The case study results revealed that the model is able to solve a seven-day planning horizon, while maintain the inventory and pressure levels within the specified bounds. However, the model can become computationally complex for days with high number of critical stations and cool vehicles.
This research contributes to inland LNG logistics by addressing the integration of routing, inventory and pressure management. Future studies should focus on a comparative analysis with heuristics, experimenting the feasibility and computational time with soft inventory and pressure bounds, and model a non-linear offload cooling effect to improve the realism of the model.
The private e-scooter in the Netherlands
Assessing the willingness to use the private e-scooter for the first-mile of train trips
The research focused on examining the role of e-scooters in “first-mile” travel through a stated preference choice experiment, given that e-scooters were newly legalised. A sample of 156 participants responded to six hypothetical travel scenarios, where they chose between familiar modes like walking, cycling, e-bikes, and e-scooters based on different factors such as carry-on ticket costs, parking times, and travel times. These scenarios were designed to reflect typical Dutch commuting choices while testing the appeal of e-scooters as a new transport option.
Analysis of the data using a Multinomial Logit (MNL) model yielded several insights into travel behaviour. There was a clear baseline preference for familiar modes, with participants showing a higher likelihood of choosing options like cycling or walking. Travel cost and time emerged as significant decision-making factors, with higher costs and longer times deterring mode choice. Notably, gender differences surfaced in this context, with males displaying greater tolerance for longer bike trips than females, indicating variations in time-cost sensitivities across demographics.
Experience with transport modes also influenced choices; prior e-scooter use was positively correlated with selecting this option again, suggesting that familiarity can increase comfort and confidence in choosing new modes. Established travel habits showed a strong impact on choice consistency, with individuals who typically walked or cycled to stations likely to maintain these habits, reinforcing the role of routine in travel preferences.
To illustrate the findings, a simulation modelled two scenarios. In the “Extreme Low” scenario, where e-scooter costs were low and parking time was minimal, walking was favoured for short distances (under 0.5 km), while cycling became dominant as distance increased. In contrast, the “Extreme High” scenario, with no fees and longer parking times, significantly boosted e-scooter attractiveness, particularly beyond 1.5 km, where it surpassed both walking and cycling. This outcome underscored the sensitivity of user preferences to economic factors, with e-scooters emerging as a highly competitive option when cost barriers were removed.
Overall, this study highlights the substantial potential for e-scooters to influence first-mile travel choices, particularly when costs are favourable and convenience is enhanced. By offering a viable alternative for medium-distance trips, e-scooters could reshape first-mile mobility in the Netherlands, complementing the well-established cycling culture and contributing to sustainable urban transport.
PSEs, such as footb ...
PSEs, such as football games or large concerts, typically result in concentrated vehicle arrivals within a limited time period, leading to increased traffic flow, potential disruptions, elevated emissions, and safety concerns in nearby areas. By optimizing parking space allocation strategies in the parking lot, this project seeks to improve overall traffic management and relieve these challenges.
To achieve this, a linear programming (LP) algorithm and a simulation-based genetic algorithm (GA) are employed to search for the optimal solution. While the LP model offers computational efficiency, it has limitations in incorporating different route conditions. To address this, an agent-based simulation is constructed to depict the interaction and movement of vehicles within the parking lot. The simulation-based GA utilizes objective values derived from the simulation, providing a more comprehensive basis for finding the optimal solution. The allocation process considers factors such as parking lot layout, vehicle entry time step, and specific parking rules including road directions within the parking lot.
Results demonstrate that the optimal strategy obtained from the simulation-based GA outperforms comparison groups. The simulation-based GA showcases its ability to converge on the optimal solution within a large solution area. The optimal strategy saving time for all vehicles, particularly during periods of high demand. Effective parking is achieved by allocating parking spaces according to the arrival order and positioning vehicles on the left or right based on their arrival order and parking space location.
By employing these methods, this project offers a valuable contribution to the field of parking space allocation in the parking lot during PSEs, enhancing the overall parking experience for event attendees.
In the current research, we aim to add and optimize timetable flexibility in traffic disturbance management for railway transport. A new definition is proposed for timetable flexibility. Timetable flexibility is defined as the ability of a timetable to be easily modified to withstand small disturbances and absorb delays, as well as to offer a larger solution space in the application of dispatching measures (retiming, reordering, rerouting) to solve larger disturbances without changing the given (re)scheduled timetable.
In order to minimize the deviation of the rescheduling plan from the rigid timetable, and maximize the timetable flexibility, the conflict resolution problem is modeled using an Alternative Graph (AG)-based Mixed Integer Linear Programming (MILP) model.
In order to investigate the impacts of different parameter inputs on timetable flexibility, a case study is conducted on a part of the Dutch railway network. To investigate the influencing factors of timetable flexibility, one illustrative application and two sensitivity analyses are conducted. Based on the results, practical implications on train dispatchers and signalers, as well as on railway passengers are concluded.
With this research, the impact of different infrastructure layouts and traffic patterns on the effectiveness of rail traffic rescheduling models is investigated. It provides insight into whether the benefit of an RTRM depends on the infrastructure and timetable in the area where it is applied.
For this purpose, an evaluation framework has been developed in which an RTRM can be tested using different infrastructure, operational and disturbance scenarios. In this framework, the RTRM is used to generate a real-time traffic plan for each scenario. These traffic plans are compared with the traffic plans of simple dispatching rules, that can be used in practice by dispatchers. For this comparison, KPIs such as the sum of consecutive delay (amount of delay that propagates within the network) and punctuality are used. This framework is applied to an alternative graph-based RTRM, which is formulated as a MILP (mixed integer linear programming).
The results show that the improvement an RTRM can offer over simple dispatching rules, varies per infrastructure layout and traffic pattern. For some infrastructure and operational scenarios, the simple dispatching rules perform as well as the RTRM, which means that for these situations, implementing an advanced RTRM does have much added value. A trend has been observed that the effectiveness of the RTRM increases as more control options are available.
With the number of passenger cars increasing worldwide, shared modes are being introduced in addition to public transport and active modes to reduce private car usage. The concept of mobility hubs was introduced to improve the acces ...
With the number of passenger cars increasing worldwide, shared modes are being introduced in addition to public transport and active modes to reduce private car usage. The concept of mobility hubs was introduced to improve the accessibility of the different available transport modes. At a mobility hub, all sorts of mobility come together, and additional facilities such as pick-up points and restaurants are added to increase the attractiveness of the hub. Based on stated-preference surveys and expert interview reports, it was identified that mobility hubs could change people's travel behaviour in the region where it is located. However, these studies only provided insights and were insufficient to assess the mobility hub’s impact on the transport network. The parking demand in residential areas is also increasing pressure on residents to switch to different modes, and these hubs could play a key role in providing alternate transport options. As a result, this research aims to study the impact of mobility hubs in a residential area on the transport network in which it is placed. This study identifies the typology of mobility hub suitable for a residential area and the components required at the hub. This study also proposes a generalized methodology for introducing mobility hubs with shared modes in aggregate transport models. A case study is performed on the Delft transport network in OmniTRANS based on the proposed methodology to understand the impacts the mobility hubs can cause. In this case study, only the shared modes are assumed to be available at the hubs, and the additional facilities are not considered. Based on the simulation results, it was found that the travel behaviour changes majorly in the residential regions where the mobility hubs have been modelled. The private car trips were found to decrease marginally, but the total number of car trips, including both private and shared cars, increased. This research recommends further research on people's behaviour in the region in the form of pilot studies before modelling for simulation as people’s behaviour varies from region to region.
Optimisation methods for the multi-period petrol station replenishment problem
A case study at AMCS
Modelling urban freight transport in the context of decarbonising transport in Europe
A case study of the Groot-Rijnmond urban area with possibilities for model transferability
Simulating smart charging optimization for electric vehicles
A quantification and statistical analysis of the cost reduction and emission reduction potential of an aggregated Dutch EV fleet
In this research, an EV aggregators perspective is leading. The EV aggregators could utilizing available flexibility in an EV fleet to deliver flexibility services. The strategy chosen to simulate is based on day ahead market optimization and passive balancing on the imbalance market. The EV fleet is assumed to be an isolated portfolio handled by the balance responsible party (BRP). The average synthetic load profile over 2018 was €41,56 per MWh and this is used as benchmark to quantify the smart charging savings in the simulations.
Different smart charging simulation set-up scenarios are designed and executed. In all simulations a real-world charging data set with 300.000 historic charging sessions was used. For each session, a new smart charging profile is determined by the optimization algorithms. The session price and session carbon intensity is calculated for both the smart charging scenarios as the business-as-usual scenarios. To compare the results of the different smart charging set-up scenarios, the average session price of all session in that simulations is used. At the same time, the smart charging savings is calculated based on the defined benchmark. The findings within this thesis support the conclusion that the used smart charging algorithms work properly and could decrease the electricity purchase price in The Netherlands. Additionally we found that the carbon intensity of the charged electricity during the smart charging schedule decreases compared to a business as usual scenario. This is a direct result of a correlation between the carbon intensity in the grid and day ahead prices in The Netherlands. EV aggregators are able to add flexibility to the demand side of the electricity system by means of smart charging, if a strong price incentive is provided. If stakeholders across the mobility and the energy sector work together, a real-world commercial implementation based on the price incentives on day ahead market and imbalance market in The Netherlands is possible. In the statistical analysis, multiple regression models show a linear relation between three independent variables (the session duration, session volume and maximum power of the charge point) and two dependent variables (the average session purchase price and savings per session). The key insights from the models empowered three main recommendations to EV aggregators to optimize the smart charging savings in the future: 1) Encourage longer session length. 2) Encourage regular overnight charging sessions behaviour, independent from the charging needs. 3) Stimulate access to high charging power. The data showed compelling differences between the 20% BEVs and the 80% PHEVs and their results were separated accordingly in this research. In all simulation set-up scenarios are the PHEVs outperforming the BEVs in terms of a lower average session price and higher cost reduction. If the smart charging strategy is executed as proposed in this thesis, the EV aggregator is exposed to the day ahead market and imbalance settlements for its portfolio. The EV aggregator is able to decrease the electricity purchase price, while acting as BRP. The exposure to the markets brings significant risk. Collaboration with an electricity supplier or BRP could potentially increase the smart charging savings for the EV aggregator. Furthermore, other revenue streams to utilize flexibility could be investigated. If stacking different flexibility strategies is possible, it could increase the smart charging value in the future.
Assignment of walking trips to pedestrian network in the context of the 4-steps travel demand model
A macro-scale approach of walking
The findings show that the stakeholders have the same goals. However, they have different experiences regarding car use and car ownership. The effects on car ownership and use of carsharing may also be influenced by other factors that are described in the conceptual model. Lastly, the findings of the differences between the selected and the control cases, show that it often appears that households in the selected cases did not have a car beforehand. Moreover, offering a shared car does not have a clear influence on its use. However, the use of the shared car and the ownership of the shared car may be explained by other factors. Moreover, the differences are not statistically significant.
Transportation and spatial impact of automated driving in urban areas
An application to the Greater Copenhagen Area
System Dynamic model. This model explored the effects of vehicle automation on the performance of the transportation and spatial system of the case-study city of Copenhagen, Denmark. Different model runs provided insight in the possible range of outcomes. Considerable problems may arise in the transportation network with the introduction of automated driving because, using the car might become very attractive. A city’s land use does, however, not change as much as many could expect. The causes of (un)desirable outcomes
were identified with the Patient Rule Induction Method. The ranges of uncertainties in the value of time in an automated vehicle and in the level of adoption of car-sharing were found to influence desirable versus undesirable futures the most. Mitigating measures should focus on these scenarios to prepare for a future with automated driving.