Search

Copyright of Ingeniería (0121-750X) is the property of Ingenieria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research demonstrated the feasibility of applying Sentinel-2 images to generate empirical models and estimate physicochemical parameters concentration, particularly nutrients in the wetland system called Bajo Sinú wetlands complex, Colombia. Spearman correlations were determined between water quality parameters, which were monitored at 17 points in the wetland on 5 February 2021, with Sentinel-2 images reflectance values from the same monitoring date; the correlations allowed the identification of statistically significant bands in the multiple linear regression algorithm implementation to determine empirical water quality models. The results show significant correlations between the optically active parameters, TSS-Turbidity, which in turn correlated with the optically inactive parameters Turbidity-NO3 and TSS-DO, as well as non-optically active parameters among themselves, TDS-NO3 and TDS-TP; the empirical models presented higher than 74.5% fit (R2), particularly DO (R2 = 0.948), NO3 (R2 = 0.858) and TP (R2 = 0.779) were the models with the highest fits (R2). These models allowed us to properly estimate the spatial distribution of nutrient-forming compounds in the wetlands complex. The determinant role played by turbidity in this type of water body is highlighted; it acts as a connecting constituent that makes the estimation of water quality parameters without spectral response through remote sensing feasible. Sentinel-2 images and multiple linear regression algorithms have been shown to be effective in estimating the concentration of water quality parameters without spectral response, such as NO3 and TP in shallow tropical wetlands, due to the processes of transformation, interaction and dependence between the different environmental variables in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

The global COVID-19 outbreak has demanded drastic actions and policies from the governments and local authorities to stem the spread of the virus. Most of the measures involve behavioural changes from citizens to reduce their social contact to a minimum. Thus, these actions influence individual activity patterns and transport systems in different ways. This paper studies the short-term impacts on the transport system caused by the different policies adopted by the Colombian government and local authorities to contain the COVID-19 spread. Using official and secondary data concerning the seven most populated cities in Colombia, we analyse the impacts on three components of the transport system: air transport, freight transport, and urban transport. Results show that national policies and local decisions have decreased the demand for motorised trips across the cities, diminishing congestion levels, reducing transit ridership, and creating a reduction in transport externalities. The country banned air transport for passengers and only allowed air cargo for medical and necessary supplies, which will have negative consequences for the economics of the airline industry. During the first three months of the COVID-19, freight was the most resilient transport component. However, freight trips diminished around 38%, affecting mainly the supply chain of nonessential products. During the pandemic, governments need to provide subsidies to maintain the system supply to avoid crowdedness and promote active transport by allocating less-used street space to cyclists and pedestrians. In the short term, transportation service providers will face a financial crisis, deepened by the pandemic, which will require government assistance for their recovery. [ABSTRACT FROM AUTHOR]

Copyright of Desarrollo Gerencial is the property of Universidad Simon Bolivar (USB) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fragile coastal areas suffer from human activities. Environmental quality is one of the most important aspects in a tourist destination of sun and sand. The quality of bathing water and sand became indicators in the worldwide competition of beach destinations. We studied the water and sand quality along the beach of Puerto Velero, in northern Colombia. Water and sand beach quality were monitored during thirteen months. This allowed identifying the most significant sources of pollution along the beach, and understanding the interrelationship between tourism and the effects on the environment. Linear correlations allow assessing the association between the number of visitors and the physicochemical and microbiological parameters. The number of visitors was directly correlated with the presence of grease and oils, both in water and sand, as well as with fecal coliforms in water. A relation between the suspended solids and the presence of fecal coliforms in water and sand was observed. This statistical approach allows understanding the origin of beach sand and swimming water pollution at tourist beaches. Overall, sand quality has an important influence and is directly related to the water quality of the beach. Both the number of tourists and their activities are main factors explaining the contamination of the water and sand. This shows the importance of management of waste and wastewater in combination with awareness raising initiatives. More research should include monitoring and evaluating of both water and sand beach and provide data to revise the existing legal framework. [ABSTRACT FROM AUTHOR]

The last stage of classical transport modelling, known as the sequential model of the four steps, estimates the flow pattern of the system. Then, in a post-processing phase all measures of system performance such as the level of service and externalities are estimated. This paper compares the estimated BPR and conical volume-delay with data taken in six multilane roads in Bogota, finding ranges of recommended function parameters values. We concluded that the values traditionally used for these functions are not the best for explaining the congestion that occurs in the environment studied. [ABSTRACT FROM AUTHOR]

A relevant issue for the strategic modeling of interregional freight transport networks is to include external costs as part of a policy that supports the mechanisms for managing and pricing to achieve the social optimum. In this paper, a freight transport model, including external cost, is developed and applied to the Colombian intercity intermodal strategic network involving equilibrium between the phases of distribution and traffic assignment. Each link on the network includes internal costs: time and operation, and external costs: congestion, accidents, air pollution and CO2emissions. Marginal costs on the freight transport network are calculated using two approaches. First, it is assumed that an additional unit of demand does not affect the equilibrium of the transport network, and then the marginal cost is estimated as the sum of marginal costs on the shortest path links. The second approach assumes that an additional unit of demand changes the network equilibrium and, consequently, the marginal costs are estimated by calculating the difference between the two equilibrium scenarios. Both approaches are applied to seven selected route corridors covering the most important national freight transport corridors. It was found that both methods produce similar results. Average external costs were rated equal to 0.014 US$/ton-km for highways, 0.000105 US$/ton-km for inland waterway transport and 0.0016 US$/ton-km for rail. In highways, external costs are equivalent to 37% of internal costs, in railways 12%, and in inland waterways they represent only 1%. [ABSTRACT FROM AUTHOR]

A combined transport network is studied with planning perspective in 2019, in order to identify optimal routes for transporting coal from centrally located sites within Colombia to export ports. Methodology based on the solution to minimum cost flow problem is used, including transport networks: road, river and railway, in a model composed of 34.000 km represented in 1.864 links. Both new rail and new export port infrastructure are included in the model. Model indicates centrally located coal within Colombia must be transported through the port of Barranquilla, using integration strategies, such as rail-river and road-river. The importance of the Magdalena River as strategic transport infrastructure is highlighted and three cargo transfer centers are identified near Barrancabermeja, Bocas del Carare and Capulco, which together could handle 18 million tons of coal per year. [ABSTRACT FROM AUTHOR]

This paper presents the results of stated-preference in a discrete choice experiments designed to examine the potential demand for a new type of passenger train between Tunja and Bogotá. The study investigates choice behaviour between three modes of transportation: bus, train and car. Each mode is represented in terms of cost, travel time and headway with a mixed logit model, which includes regularly for individuals. The model was used to experiment with different scenarios, finding the modal split for each. [ABSTRACT FROM AUTHOR]

• We analyze 2,339 crashes recorded in Cartagena, Colombia. • We focus on fatal, injury, and property-damage-only traffic crashes. • Factors relating to victim, vehicle, road infrastructure, traffic and control, day and time, and environment were considered. • Probability of fatal crashes is higher near to pedestrian bridges, traffic lights, and crosswalks. Traffic fatalities are the second cause of violent deaths in Colombia. However, due to the signing of the peace agreement and the growing number of fatalities in road crashes, it is possible that soon traffic fatalities will be the primary cause of violent deaths in the country, particularly in urban areas. This study is an exploratory analysis focused on identifying the main factors associated with the severity of traffic crashes in urban areas, using Cartagena as a case study. We analyzed three levels of crash severity, namely fatal, injury, and property-damage-only, considering factors in several different dimensions: victim, vehicle, road infrastructure, traffic and control, day and time, and environmental factors. A modeling approach based on multinomial ordered discrete models was used to properly identify the main factors associated with the severity levels. We found that the probability of fatal accidents is higher on streets with speed limits over 40 km/h, and that males and people aged 60 years or older are the victims with the most significant risk of fatal crashes. Motorcycles were also identified as vehicles with the highest probability of fatal crashes in the city. We showed that the probability of fatal crashes occurring is higher on streets where pedestrian bridges, traffic lights, and crosswalks are present. These findings are worthy because, in Colombia and other developing countries, the authorities normally expect to reduce the probability of fatal accidents through investments in pedestrian bridges, signaling devices, and crosswalk markings. However, according to our results, it possibly will not occur unless further countermeasures are taken. Based on these findings, reducing speed limits, operational improvements at signalized intersections, zero tolerance for traffic violations related to pedestrians, an awareness campaign on pedestrian safety focused on males and people aged 60 or older, and improving motorcycle safety are the countermeasures we proposed. Furthermore, as the authorities make significant efforts to investing in pedestrian bridges, we propose a further investigation into the traffic crashes in streets where there is this infrastructure since more severe events occur near them. [ABSTRACT FROM AUTHOR]