Using Modelling Techniques to Analyze Urban Freight Distribution. A Case Study in Pamplona (Spain)

The city of Pamplona, in Spain, is currently experiencing several changes regarding sustainable mobility such as pedestrianization of some streets in the city center, and access control to the Old Town for motor vehicles through the use of automatic number-plate recognition. However, some groups including local neighbors and businesses are raising complaints as they are being affected by these measures. This is also the case for couriers and logistics companies which have now to comply with new regulations regarding delivery routes throughout the Old Town. This paper will present a comprehensive study of the situation that is being carried out, and in which social perceptions and freight traffic patterns in the Old Town of Pamplona are analyzed to understand how urban freight distribution could be improved in the area. For this purpose, we make use of a survey-based research to the stakeholders, i.e. pedestrians, logistics companies, retailers, and authorities of Pamplona. Results highlight pollution derived from transportation, lack of parking spaces as well as invasion of public spaces in the city center as the key issues for improving freight transportation in the Old Town. Finally, placing a distribution center in the Old Town and the promotion of the cycle-logistics are considered as the future of the urban distribution in Pamplona

An iterative biased-randomized heuristic for the fleet size and mix vehicle-routing problem with backhauls

This paper analyzes the fleet mixed vehicle-routing problem with backhauls, a rich and realistic variant of the popular vehicle-routing problem in which both delivery and pick-up customers are served from a central depot using a heterogeneous and configurable fleet of vehicles. After a literature review on the issue and a detailed description of the problem, a solution based on a multistart biased-randomized heuristic is proposed. Our algorithm uses an iterative method that relies on solving a series of smaller instances of the homogeneous-fleet version of the problem and then using these subsolutions as partial solutions for the original heterogeneous instance. In order to better guide the exploration of the solutions space, the algorithm employs several biased-randomized processes: a first one for selecting a vehicle type; a second one for sorting the savings list; and a third one to define the number of routes that must be selected from the homogenousfleet subsolution. The computational experiments show that our approach is competitive and able to provide 20 new best-known solutions for a 36-instance benchmark recently proposed in the literature

An iterative biased-randomized heuristic for the fleet size and mix vehicle-routing problem with backhauls

This paper analyzes the fleet mixed vehicle-routing problem with backhauls, a rich and realistic variant of the popular vehicle-routing problem in which both delivery and pick-up customers are served from a central depot using a heterogeneous and configurable fleet of vehicles. After a literature review on the issue and a detailed description of the problem, a solution based on a multistart biased-randomized heuristic is proposed. Our algorithm uses an iterative method that relies on solving a series of smaller instances of the homogeneous-fleet version of the problem and then using these subsolutions as partial solutions for the original heterogeneous instance. In order to better guide the exploration of the solutions space, the algorithm employs several biased-randomized processes: a first one for selecting a vehicle type; a second one for sorting the savings list; and a third one to define the number of routes that must be selected from the homogenousfleet subsolution. The computational experiments show that our approach is competitive and able to provide 20 new best-known solutions for a 36-instance benchmark recently proposed in the literature

Enriching Simheuristics with Petri net models: potential applications to logistics and supply chain management

Some classic and complex problems in Operations Research consist of simplified versions of real logistic and supply chain management applications. One common and successful, but approximated approach for coping with these problems considers the system of interest isolated from its environment. In such a case, the links to the real world may be reduced to a set of parameters associated with probabilistic distributions. Simheuristics is a solving methodology able to provide efficiently near-optimal solutions for these constrained problems. This paper presents a methodology combining Simheuristics with a Petri net model, describing the environment of a logistic system. An extended version of the capacitated vehicle routing problem with stochastic demands is stated adding a Petri net model. Petri nets are widely used for modeling parallelism and concurrency, providing a realistic description of this environment, which may change the behavior of the isolated system and the scope of the decision-making

Developing an information system for monitoring student's activity in online collaborative learning

In this paper we address the issue of monitoring students' and groups' activity in online collaborative learning environments. This issue is especially important in the collaborative e-learning context, since an efficient monitoring process can provide valuable information to online instructors who may guide and support the development of collaborative learning projects. We have developed and tested an information system model which facilitates the automatic generation of weekly monitoring reports derived from data contained in server log files. These reports provide online instructors with visual information regarding students¿ and groups' activity, thus allowing for a quick and easy classification of students and groups according to their activity level. Therefore, entities with a low activity level are identified as soon as possible and just-intime assistance can be established for them. Furthermore, instructors can use these monitoring reports to forecast potential problems 'such as students' dropouts or possible conflicts inside the groups due to unbalanced distribution of tasks' and take operational and tactical decisions oriented to avoid them

Enriching Simheuristics with Petri net models: potential applications to logistics and supply chain management

Some classic and complex problems in Operations Research consist of simplified versions of real logistic and supply chain management applications. One common and successful, but approximated approach for coping with these problems considers the system of interest isolated from its environment. In such a case, the links to the real world may be reduced to a set of parameters associated with probabilistic distributions. Simheuristics is a solving methodology able to provide efficiently near-optimal solutions for these constrained problems. This paper presents a methodology combining Simheuristics with a Petri net model, describing the environment of a logistic system. An extended version of the capacitated vehicle routing problem with stochastic demands is stated adding a Petri net model. Petri nets are widely used for modeling parallelism and concurrency, providing a realistic description of this environment, which may change the behavior of the isolated system and the scope of the decision-making

A simheuristic for routing electric vehicles with limited driving ranges and stochastic travel times

Green transportation is becoming relevant in the context of smart cities, where the use of electric vehicles represents a promising strategy to support sustainability policies. However the use of electric vehicles shows some drawbacks as well, such as their limited driving-range capacity. This paper analyses a realistic vehicle routing problem in which both driving-range constraints and stochastic travel times are considered. Thus, the main goal is to minimize the expected time-based cost required to complete the freight distribution plan. In order to design reliable Routing plans, a simheuristic algorithm is proposed. It combines Monte Carlo simulation with a multi-start metaheuristic, which also employs biased-randomization techniques. By including simulation, simheuristics extend the capabilities of metaheuristics to deal with stochastic problems. A series of computational experiments are performed to test our solving approach as well as to analyse the effect of uncertainty on the routing plans

SAEDES++: determining complex system availability via simulation

Complex systems are everywhere among us: telecommunication networks, computers, transporting vehicles, and electrical appliances are well known examples. Designing reliable systems and determining their availability are both very important tasks for managers and engineers, since reliability and availability have a strong relationship to other concepts such as quality and safety. Furthermore, these tasks are extremely difficult, due to the fact that analytical methods can become too complicated, inefficient or even inappropriate when dealing with sophisticated systems. In this paper we present the basic ideas behind a simulationbased method, called SAEDES, which can be very useful when determining availability for a wide range of complex systems. The method is implemented in C/C++ using two different algorithms, SAEDES_A1 (component-oriented) and SAEDES_A2 (system-oriented). Two case-studies are introduced and analyzed using both algorithms, which allows us to compare the associated results

Developing an information system for monitoring student's activity in online collaborative learning

In this paper we address the issue of monitoring students' and groups' activity in online collaborative learning environments. This issue is especially important in the collaborative e-learning context, since an efficient monitoring process can provide valuable information to online instructors who may guide and support the development of collaborative learning projects. We have developed and tested an information system model which facilitates the automatic generation of weekly monitoring reports derived from data contained in server log files. These reports provide online instructors with visual information regarding students¿ and groups' activity, thus allowing for a quick and easy classification of students and groups according to their activity level. Therefore, entities with a low activity level are identified as soon as possible and just-intime assistance can be established for them. Furthermore, instructors can use these monitoring reports to forecast potential problems 'such as students' dropouts or possible conflicts inside the groups due to unbalanced distribution of tasks' and take operational and tactical decisions oriented to avoid them

Using Modelling Techniques to Analyze Urban Freight Distribution. A Case Study in Pamplona (Spain)

The city of Pamplona, in Spain, is currently experiencing several changes regarding sustainable mobility such as pedestrianization of some streets in the city center, and access control to the Old Town for motor vehicles through the use of automatic number-plate recognition. However, some groups including local neighbors and businesses are raising complaints as they are being affected by these measures. This is also the case for couriers and logistics companies which have now to comply with new regulations regarding delivery routes throughout the Old Town. This paper will present a comprehensive study of the situation that is being carried out, and in which social perceptions and freight traffic patterns in the Old Town of Pamplona are analyzed to understand how urban freight distribution could be improved in the area. For this purpose, we make use of a survey-based research to the stakeholders, i.e. pedestrians, logistics companies, retailers, and authorities of Pamplona. Results highlight pollution derived from transportation, lack of parking spaces as well as invasion of public spaces in the city center as the key issues for improving freight transportation in the Old Town. Finally, placing a distribution center in the Old Town and the promotion of the cycle-logistics are considered as the future of the urban distribution in Pamplona