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Until now, the algorithms used to compute an equilibrate route assignment do not return an integer solution. This disagreement constitutes a non-negligible drawback. In fact, it is shown in the literature that a fractional solution is not a good approximation of the integer one. The purpose of this paper is to find an integer route assignment.

The static route assignment problem is modeled as an asymmetric network congestion game. Then, an algorithm inspired from ant supercolony behavior is constructed, in order to compute an approximation of the Pure Nash Equilibrium (PNE) of the considered game. Several variants of the algorithm, which differ by their initializing steps and/or the kind of the provided algorithm information, are proposed.

An evaluation of these variants over different networks is conduced and the obtained results are encouraging. Indeed, the adaptation of ant supercolony behavior to solve the problem under consideration shows interesting results, since most of the algorithm’s variants returned high-quality approximation of PNE in more than 91 percent of the treated networks.

The asymmetric network congestion game is used to model route assignment problem. An algorithm with several variants inspired from ant supercolony behavior is developed. Unlike the classical ant colony algorithms where there is one nest, herein, several nests are considered. The deposit pheromone of an ant from a given nest is useful for the ants of the other nests.

This study is in line with the debate concerning the compatibility between the qualitative and quantitative food production objectives. The purpose of this paper is to identify the causal relationship that may exist between public food safety regulations (specifically, the maximum authorised levels of chemical or microbiological contaminants), and the expected price in the spot markets (wholesale markets, for example).

The authors propose a theoretical industrial economic model that identifies the causal link which may exist between public food safety regulations (e.g. the maximum authorised levels of chemical or microbiological contaminants), the expected price in domestic markets, and the rate of exclusion of local producers. This general model allows one to characterize the price formation process in markets subject to maximum residue level constraints by focusing on the role of the official inspection systems established by public authorities.

The authors show how strengthening official controls does not systematically impact negatively on producers’ participation and does not always decrease supply. Moreover, the authors show that reinforcing the maximum permitted contamination thresholds is not always sufficient for ensuring consumer health.

The originality of the model is that it shows how all variables (economic and sanitary variables) interact in the formation of agricultural prices and determine the final size of the productive system (number of active producers). The characterisation of the market price as a function of producers’ investment efforts and of the level of official control reliability allows one to determine both the total supply and the proportion of this supply that is contaminated (i.e. does not comply with the maximum threshold of contamination).