Browsing by Author "Giesen, Ricardo"

Now showing 1 - 5 of 5
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    Choosing the Right Express Services for Bus Corridor with Capacity Restrictions
    (SAGE PUBLICATIONS INC, 2010) Larrain, Homero; Giesen, Ricardo; Carlos Munoz, Juan
    In public transit systems with high demand levels, the use of express bus services that serve only a subset of stops along certain routes appears to be a promising alternative given the benefits that they offer to both users and operators. In practice, express services in systems such as Transmilenio (Bogota, Colombia), Transantiago (Santiago, Chile), and Metro Rapid (Los Angeles, California) have proved highly appealing. To determine what types of express services would be attractive on a bus corridor given the characteristics of its demand, four parameters are defined for identifying corridor demand profiles: the base load profile shape, the scale of demand, the demand imbalance between the outbound and inbound directions, and the average trip length. A series of indicators was also defined to measure the potential benefits of express services in the scenarios studied. The results of the experimental simulations show that a crucial parameter for determining the potential benefits of express services is the average trip length along the corridor. The incorporation of express services is particularly attractive in corridors with demand profiles that increase or decrease monotonically. In addition, the results suggest that in other cases, the complexity of the demand shape could allow for more complex express service patterns.
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    Coping with Disruptions Performance Comparison of Strategies for Online Inventory Routing Systems Under Demand Surges
    (SAGE PUBLICATIONS INC, 2010) Giesen, Ricardo; Mahmassani, Hani S.; Jaillet, Patrick
    In real time distribution operations, It is generally assumed that demand process parameters can be precisely estimated However, this is rarely the case, particularly for products with a short life cycle Experiments were done to investigate the performance of various strategies for online distribution operations under disruptions caused by surges in demand patterns at a particular facility Two sets of strategies are considered (a) optimization based strategies, in which an off line optimization problem is formulated and used to update routing and inventory allocation plans, and (b) fixed tour strategies, in which a priori sets of routes to provide retailers with recourse actions depending on different degrees of real time information capabilities for controlling the system are used These are compared against two benchmark policies Simulation results for two scenarios (high and low inventory holding cost products) show that strategies that use real time information to update delivery plans systematically outperform strategies in which routes are not modified after the vehicle leaves the depot The differences tend to be higher in scenarios of products with low Inventory holding costs For replanning strategies, the benefits of en route plan updates are significant, in particular the possibility of diverting the vehicle In the case of fixed tour strategies, the possibility of updating tour Intervals provides potentially great savings Replanning strategies systematically outperform fixed tour strategies
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    Design of limited-stop services for an urban bus corridor with capacity constraints
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010) Leiva, Carola; Carlos Munoz, Juan; Giesen, Ricardo; Larrain, Homero
    In high-demand bus networks, limited-stop services promise benefits for both users and operators, and have proven their attractiveness in systems such as Transmilenio (Bogota, Colombia) and Transantiago (Santiago, Chile). The design of these services involves defining their itinerary, frequency and vehicle size, yet despite the importance of these factors for the network's efficiency, no published works appear to provide the tools for designing high-frequency unscheduled services on an urban bus corridor, minimizing social costs.
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    Impact of COVID-19 on the number of days working from home and commuting travel: A cross-cultural comparison between Australia, South America and South Africa
    (2021) Balbontin Tahnuz, Camila; Hensher, David A.; Beck, Matthew J.; Giesen, Ricardo; Basnak, Paul; Vallejo Borda, Jose Agustin; Venter, Christoffel
    The COVID-19 pandemic has changed the way we go about our daily lives in ways that are unlikely to return to the pre-COVID-19 levels. A key feature of the COVID-19 era is likely to be a rethink of the way we work and the implications on commuting activity. Working from home (WFH) has been the 'new normal' during the period of lockdown, except for essential services that require commuting. In recognition of the new normal as represented by an increasing amount of WFH, this paper develops a model to identify the incidence of WFH and what impact this could have on the number of weekly commuting trips. Using data collected in eight countries (Argentina, Australia, Brazil, Chile, Colombia, Ecuador, Peru and South Africa), we developed a Poisson regression model for the number of days individuals worked from home during the pandemic. Simulated scenarios quantify the impact of the different variables on the probability of WFH by country. The findings provide a reference point as we continue to undertake similar analysis at different points through time during the pandemic and after when restrictions are effectively removed.
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    Model for Optimization of Locations of Schools and Student Transportation in Rural Areas
    (NATL ACAD SCIENCES, 2012) Mandujano, Pablo; Giesen, Ricardo; Ferrer, Juan Carlos
    Low population densities make it difficult to design efficient networks of schools in rural areas. The most common solution is to operate small schools with children in multiple grades in each classroom, even though this solution may not be the least expensive. School consolidation proposals are difficult to implement because communities may have emotional bonds with their local schools and the impacts on secondary services, such as student transportation, are difficult to evaluate. In rural areas, particularly in Brazil, reductions in the costs associated with school operations and student transportation could allow boards of education to allocate more resources to improve educational practices and teaching materials. This paper presents a methodology for optimizing the location of schools and student transportation in rural areas. This methodology is based on two mixed-integer programming models, which are used sequentially. The first one deals with the school location and sizing problem, and the second one deals with the school bus routing and shift programming problem. The methodology was applied with data from Barao de Grajau, which is in the northeast region of Brazil, and provided savings in operating costs of 10% to 17%.