Unified closed-form expression of logit and weibit and its extension to a transportation network equilibrium assignment

• A unified closed-form expression of logit and weibit with the GEV distributed utility.
• Heteroscedastic variance and flexible utility function are allowed in the model.
• Traffic assignment with the generalized (or unified) logit model is formulated.
• The above formulation includes the generalized entropy (Tsallis entropy) term.
• The utilities, route choice, and assignment are generalized in Tsallis statistics.

This study proposes a generalized multinomial logit model that allows heteroscedastic variance and flexible utility function shape. The novelty of our approach is that the model is theoretically derived by applying a generalized extreme-value distribution to the random component of utility, while retaining its closed-form expression. In addition, the weibit model, in which the random utility is assumed to follow the Weibull distribution, is a special case of the proposed model. This is achieved by utilizing the q-generalization method developed in Tsallis statistics. Then, our generalized logit model is incorporated into a transportation network equilibrium model. The network equilibrium model with a generalized logit route choice is formulated as an optimization problem for uncongested networks. The objective function includes Tsallis entropy, a type of generalized entropy. The generalization of the Gumbel and Weibull distributions, logit and weibit models, and network equilibrium model are formulated within a unified framework with q-generalization or Tsallis statistics.