Helena Beatriz Bettella Cybis

Calibration Procedure for Gipps Car-Following Model

A methodology is presented for calibrating the car-following model proposed by Gipps. This calibration procedure is concerned with steady-state conditions. A steady state occurs when the leader and follower vehicles travel at similar and near-constant speeds, maintaining similar space headways between each other. Steady-state calibration is important because it determines roadway capacity, speed at capacity, and jam density (spatial extent of queues when fully stopped). The calibration process allows the identification of adequate values for deceleration rates, b (maximum deceleration rate the driver is willing to use), b′ (the maximum deceleration rate estimated for the leader), and driver reaction time (T). Two different behavioral assumptions were developed concerning the deceleration rates: b equal to b′ and b different from b′. The first hypothesis assumes that the leader will be as aggressive as the follower. The second assumes that the driver considers the leader to have a different maximum deceleration rate. The results are presented in tables and graphs that correlate the car-following parameters to the fundamental traffic stream variables for the different behavioral assumptions. The procedures are then tested on sample field data to demonstrate the adequacy of the calibration procedures.

The influence of built environment and travel attitudes on walking: A case study of Porto Alegre, Brazil

ABSTRACT Studies conducted in cities from developed countries reveal associations between travel behavior and built environment. A priori we would expect that most of these associations hold for cities from developing countries but we do not have any basis to suppose whether or not they will be quantitatively the same because of differences in the nature of urban form between cities of developed and developing countries, and potential differences in attitudes and travel preferences from their travelers. This article analyzes the relationship between walking patterns, travel attitudes, and neighborhoods urban structure in Porto Alegre, Brazil, under the assumption that built environment affects travel attitudes, instead of the more typical assumption that goes the other way around. We develop a two-step ordered choice model enriched with attitudinal variables to integrate travel attitudes, built environment, and travel behavior. A multiple indicator multiple cause (MIMIC) model is used to identify travel attitude as latent constructs that feed a frequency-of-walking ordered logit model with both the built environment and travel attitudes as explanatory variables. Our results support the a priori assumption that we would replicate many of the results already reported in the literature. However, we obtained the same differences in the magnitudes of some key elasticities. The results of the elasticities computed for the number of walking trips with respect to the built environment variables were smaller than in other studies. Only the effect of population density on walking frequency seems to be marginally higher.

Pedestrian route choice model based on friction forces

This paper presents a pedestrian route choice model devised to represent the influence of the impedance generated by other pedestrians on the route choice process. This model is inspired by friction force equations, and considers that pedestrians avoid passing near other pedestrians with high relative velocity. The route choice process is based on a weighting of the impedance generated by pedestrians and the path length. A social force model was used to model pedestrian walking behavior. The model is able to reproduce emergent behavior among agents, allowing the assumption that the friction equations may provide a suitable approach to route choice behavior and can also be used as an indirect measure of pedestrian delay.

Model to evaluate roadway concessions in Brazil

This paper describes the construction and application of a model to evaluate roadway concessions. The model is based on the perception of users and experts about physical aspects of roads and services provided by Brazilian concessionaires. Information was gathered from previous studies, interviews with road users, and focus groups with experts. The paper describes the conceptual stages of the model, presents a field application, and discusses the results generated for one case study. The model allows a dynamic monitoring program of the conditions of roads, road segments, and entire concessions, considering the individual or joint perception of users and experts. The model is transferable to other scenarios where it is important to have a tool to help the negotiation process between public and private sectors concerning new roadway investments by the concessionaires.

Calibration of a Pedestrian Route Choice Model with a Basis in Friction Forces

This paper presents a pedestrian route choice model and its calibration with real data. The model explicitly represents interaction between pedestrians as an impedance force influences their route choice. This model approach was inspired by friction force equations and considered efforts by pedestrians to avoid passing near other pedestrians with high relative velocity. The route choice process was a function of impedance force and route length. A social force model was used to model pedestrian walking behavior. The calibration had its basis in data acquired from a real experiment developed in a simplified network. Data collection had its basis in video analysis. The paper presents and discusses results from the calibration processes. The model presented in this paper differs from other pedestrian route choice models because it seamlessly incorporates a pedestrian social force model into the route choice decision process.

Simulation Model for Vehicle and Pedestrian Interaction Considering Road Crossing Activities

This paper addresses the pedestrian road-crossing modeling problem. The model presented in this paper has been devised to provide a sound representation of interaction among pedestrians and a more realistic approach for interaction between pedestrians and vehicles. The present research proposes the analysis of two different pedestrian crossing behaviors. One crossing behavior considers a fixed area for pedestrians cross a road. The second one considers pedestrians searching for a gap while walking on the sidewalk. This paper presents the analysis of 180 simulations, considering 18 different parameters settings. From the results of the present research, the analysis of variance (ANOVA) shows that both variables, average headway of vehicles and pedestrian behavior, were statistically significant.

Avaliação dos impactos de uma proposta de escalonamento de horários em um campus universitário

O artigo apresenta uma avaliacao dos provaveis impactos do escalonamento dos horarios das aulas noturnas em uma Universidade. Neste trabalho sao investigados, a aceitacao dos usuarios quanto a possiveis alteracoes, e os impactos do escalonamento na rede viaria no entorno do campus. O trabalho envolveu a construcao de diversos cenarios de alteracoes nos horarios de inicio das aulas. Os cenarios foram construidos visando atender as preferencias da populacao universitaria e reduzir a interferencia do pico de chegada de alunos no sistema viario. A avaliacao dos impactos destes cenarios no trafego foi realizada atraves de simulacao, com a utilizacao do modelo TSIS/NETSIM. As analises foram baseadas em dois indicadores de desempenho: as velocidades medias e o tempo de atraso medios na rede.