A MODEL FOR THE ANALYSIS OF REGIONAL ACCESSIBILITY FOR FREIGHT TRANSPORTATION

Transcription

1 A MODEL FOR THE ANALYSIS OF REGIONAL AESSIBILITY FOR FREIGHT TRANSPORTATION Vânia Barcellos Gouvêa AMPOS 1 Alexandre oelho SANTOS 2 Eliana ZANDONADE 3 Abstract. Accessibility models are very important to evaluate transportation systems. Even though, there are a lot of researches on this matter, there are many aspects that remain unexplored. Most of the accessibility indicators are related to urban transportation systems and not concerned to freight transport in a regional context. By a literature review it was identified some accessibility models used in several studies and the principal variables that compose them. Thus, starting from this analysis, considering the freight transport characteristics, a model to evaluate the accessibility in the context of regional freight transport is proposed. 1. Introduction The theme accessibility appears in the literature as an important tool in the urban or regional planning with the characteristic of incorporating the conditions of the transportation systems and the distribution of the activities in a study area, allowing to know the interaction degree among the analyzed regions. In spite of the applications of accessibility concept in several fields of the knowledge (urban and transportation planning, geography, military planning, computation, medicine, humanities, among other), this theme is considered, in a certain way, intuitive and difficult of efficiently measuring (Handy and Niemeier, 1997[2]; Raia Jr., 2000[3]). Nevertheless, it is a subect that has maintained current, and being researched and discussed in several works along the years. Most of the accessibility models formulation varies according to the purpose of the accomplished study and to the involved sceneries. It can be observed, in most of the works, applications about the people's movement in urban areas. Therefore, this work presents the application of the accessibility concepts out of the urban context and out of the focus in the people's mobility. It is the case of the evaluation of the accessibility for freight transportation in regional context. 1 Instituto Militar de Engenharia, Rio de Janeiro, Brasil, vania@ime.eb.br 2 Universidade Federal do Espirito Santo,Vitória,Brasil, alexandrecsantos@yahoo.com.br 3 Universidade Federal do Espirito Santo,Vitória,Brasil. elianaz@cce.ufes.br

2 In the literature, the acessibility model compositions, basically, include, parameters related to the space separation and to the systems of activities analyzed. Among the main components considered in the composition of the models, there are: space separation, function impedance, attractiveness of the destinies and still a relative element to the users behavior. 2. Some onsiderations about Freight Transportation and Accessibility models In the search for an accessibility measure for freight transportation, it tried to adapt the variables commonly found in the urban accessibility models, regarding parameters representing space separation _ the travel time, cost and distance, which can be considered in the evaluation of the freight transportation performance. However, some considerations related to the type of the load and to the modality used in the transport, could be important. For example, the travel time can become a factor of great relevance for certain goods like the flowers and it influences the decision about the transportation. The accessibility can still be evaluated, in the context of an intermodal transportation network for freight transport, when considering, for example, the reduction of costs by the use of a given transport modality. In some cases, an accessibility measure could aid in the evaluation of the efficiency of each modal transportation option. In the treatment of the accessibility, Gutierrez et al. (1998)[1] used the influence of the quality of the highway infrastructure and the amount of traffic on the travel time for representation of the impedance for highways. For railways, Gutierrez et al. (1998)[1] selected variables related with the amount of railway lines, daily capacity of them, frequency of the trains and travel time. For the component of attractiveness of the destiny, there is a certain flexibility of choosing the measure of attractiveness for the load, because the variety of measures proposed in the literature. Analyzing the attractiveness, the considerations for the load transported could be analyzed in two ways. In a first approach, it refers to the freight for internal market, whose destiny options can vary among consuming centers, industries and central of distribution, and others. In this sense, the possible attractive variables to be considered could be, for example: Gross Domestic Product of the destiny area (GDP), average income, amount of industries, working power, storage capacity, among others. The second approach, it refers to the freight destined to the external market (for export). In this way, the seaports in the national territory are considered as the destiny of the exported load. In these cases, attractive variables like: operational costs, storage capacity, frequency of vehicles, operational capacity, level of safety, and others could be considered. The impedance function adds to the model the effect of the space separation between the origin points and the destination points, reflecting the easiness or difficulty of displacement between the location points. 3. The proposed model for analysis of the accessibility for the freight transportation In general, according to the needs of the different areas, the movement of the loads happens in function of the demand and the variety of load, and the localization of consumer and producers.

3 In this sense, there are different interactions between origins and destinies, which define the load transportation routes. Thus, in the illustration 1 it can be observed a simplification of different contexts of the transport of loads related to the concepts of the relative accessibility and the integral accessibility. 1 i (a) i 2 (b) n i 1 i 1 1 i 2 i 2 2 i m (c) Figure 1. onfigurations of routes representing possible interactions between origins and destinies of the load. i m (d) n In the example of the fig.1(a) it can be visualized the relative accessibility (A) between an origin (i) and a destiny (). In the example Fig 1(b), the integral accessibility (Ai) from a given origin (i) in relation to the several destinies ( n ), is represented as a result of the sum of the relative accessibilities. In the network presented in Fig. 1(c) the integral accessibility is also observed, but, in this case, related to the destiny of the load (A), and so, the interaction is among several origins (i m ) and an only destiny (). In the example Fig 1(d) the interaction is observed between several origins and several destinies. Starting from the analyses of the accessibility models and considering the characteristics of the transport of loads, it is proposed the following formulation of the model of accessibility load transportation in regional level: A m = 1 = r T,k. k = 1 Where: A - relative accessibility between i and ; D - demand of the product in the destiny ; D r t D, k α (1)

4 r - number of transport routes between i and ; T,k - travel time of the freight transport from i to in the route k; t,k - time estimated for the transport of the load between i and in the route k, considering the route is on ideal operational and traffic conditions α - factor of ponderation of the r, obtained starting from a value R gives by the function: R = 1 + r. min, max, (2) in that: min - minimum fare/ton paid for the transport of the load from i to, among the options of available routes and max, - maximum fare/ton paid for the transport of the load from i to, among the options of available routes. In the composition of the model, it appears two components representative of the transport system: the number of available routes for the transport of the load (r ) and the relationship among the travel times (T / t ) which understands the concept of efficiency of the transportation network, and besides, a ponderation factor (α ). onsidering that the accessibility of the load transportation is analyzed under the view of a productive pole, the attractiveness component in its composition can be considered as the demand (D) for the product in the destiny (). For that, it is supposed to exist a load transportation flow from a productive pole (i), and the necessity of transporting them because there is a demand for this load in the destiny (). This variable serves also to the flows addressed to the internal as for the external market, and also its can be used for the different types of shipments. Besides, based in the concept of neutralization of the effect of the geographical location (Gutierrez et al., 1998)[1]; Sanches and Ferreira, 2003[4]), a component is inserted in the model with the obective of evaluating the efficiency of the transport network. This component is represented by the relationship among the travel time practiced by the transporter between the origin and destiny (T ) and the estimated travel time (t ) considering that the route has a great operational conditions of transport. Another component of the model related to the transportation system characteristics is the number of options of available routes between the origin and destiny (r ). And, because of this, it is considered a parameter c that ponders the number of options of routes in function of the relationship among the smallest transportation fare (min ) and the largest fare (max ) of transport among the options of routes. The consideration of this later component has the proposal to ponder, in the result of the accessibility model, the effect of existing more than one option of transportation route between a pair of origin and destiny. In this way, the fact of existing more than one option of transport route oining a pair of origin and destiny, cannot be an advantage if there is a great difference between the minimum and maximum transportation fares in these routes, that is, a transport route with a very higher fare than another should have a smaller influence in the accessibility measure. To avoid some distortions in the α values because of the number of considered routes (r ), it was adopted the following restrictions of values for that factor:

5 r ; R > r α = R ; R r (3) For situations in that: a) r 2, the alpha value will be given by the following expression, respecting the restrictions given above. R = 1 + r. min, max, (4) b) r > 2, it is necessary the following analysis: - if R <(r - 1), the route of larger transportation fare is not considered and the following expression is calculated until obtaining a satisfactory values, according to this restrictions adopted: R = 1 + ( r 1 ). min, max, With this analysis it tries to avoid those routes with very high fares influence the result of the accessibility negatively, penalizing other options of routes for certain pair of origindestiny analyzed. The A index resulted from the model has the proposed to compare different areas in the regions and evaluate which has the better and the worst accessibility and, according to that, it will be possible to orient the investments on the transportation infra-structure. 4. An Application of the model For the application of the model it was considered, as an example, the transport of agriculture products from some productive municipal districts located in the Espírito Santo State in Brazil, with destiny in EASA, a entral of Provisioning and ommercializing of that State, located in the municipal district, named ariacica. It were collected information from 27 productive municipal districts and it was considered the three more important products (coconut, tomato and papaya) commercialized by EASA in the year of For each product it was chosen the ten higher productive municipal districts. For that, three intermodal transportation networks were considered for application of the proposed model according to each product, the characteristics of available transportation system and the production of the municipal districts. Each network is constituted of ten origins (the productive municipal districts) and only one destiny ( EASA). The figure 2 presents the map representing the result related to the freight transportation accessibility analyses for the transport of tomato production. The analysis of the accessibility is obtained by the calculation of the relative accessibility of each productive pole in relation to the destiny of the load (EASA). In the figure 1 it is possible to visualize, by the color of municipal districts, the accessibility level of each productive municipal district. With the proposed model is possible to make a sensitivity analysis of changes on each variable component of the model. (5)

6 Before the application of the model, it was tested the performance of the model by simulating values for each variable and it was conclude that the model gives a good result for the obective it was proposed. Accessibility indices Figure 2- Accessibility indices for the transport of the tomato production in the State of Espirito Santo, Brazil References [1] Gutiérrez, J.; A. Monzón e J. M. Piñero (1998) Accessibility, Network Efficiency and Transport Infrastructure Planning. Environment and Planning A, v. 30, p [2] Handy, S. L. E Niemeier, D. A. Measuring accessibility: an exploration of issues and alternatives. Environment and Planning A, v. 29, p , [3] Raia Jr, A. A. (2000) Acessibilidade e Mobilidade na Estimativa de um Índice de Potencial de Viagens Utilizando Redes Neurais Artificiais e Sistemas de Informações Geográficas. Tese (Doutorado) - Escola de Engenharia de São arlos, Universidade de São Paulo, São arlos - SP. [4] Sanches, S. P. e M. A. G. Ferreira (2003) Avaliação do Padrão de Acessibilidade em Um Sistema de Transporte de Alunos da Zona Rural. Anais do XVII ongresso de Pesquisa e Ensino em Transportes, ANPET, Rio de Janeiro, v. 2, p