Soroush Rashidi

Bus Dwell Time Modeling Using Gene Expression Programming

A gene expression programming (GEP)-based approach that shows prospects how to estimate bus dwell time (BDT) more accurately and overcome some of the issues associated with the multiple linear regression (MLR) method is proposed in this article. The model is calibrated and validated using the data collected from 22 bus stops in Auckland and compared against the MLR model based on five different performance measures: mean error, mean absolute error, root mean square error, mean absolute percentage error, and R² value. The restrictions to stick with a predefined model and the need to satisfy assumptions made on multicollinearity, homoscedasticity, and the normality of random error are often difficult to satisfy.

Modeling Bus Dwell Time with Decision Tree–Based Methods

A large proportion of transit travel time is made up by dwell time for passengers boarding and alighting. More accurate modeling and estimation of bus dwell time (BDT) can enhance the efficiency and reliability of the public transportation system. Multiple linear regression (MLR) has been the most commonly used method in the literature for modeling and estimating BDT. However, the underlying assumptions of the MLR method, such as multicollinearity and normality of random error, cannot always be satisfied for real applications. This study developed and implemented two methods based on decision trees (DTs), namely, classification and regression tree and chi-squared automatic interaction detector, for the first time for BDT modeling and estimation. The models were compared with the traditional MLR model after calibrating and validating the new models against the data collected from four bus stops in Auckland, New Zealand. Various error measurements were used to evaluate the accuracy of the models. The DT-based methods eliminated the limitations of the MLR method and provided reliable and accurate estimation of BDT.

Analyzing pedestrian crash injury severity under different weather conditions

ABSTRACT Objective: Pedestrians are the most vulnerable road users due to the lack of mass, speed, and protection compared to other types of road users. Adverse weather conditions may reduce road friction and visibility and thus increase crash risk. There is limited evidence and considerable discrepancy with regard to impacts of weather conditions on injury severity in the literature. This article investigated factors affecting pedestrian injury severity level under different weather conditions based on a publicly available accident database in Great Britain. Method: Accident data from Great Britain that are publicly available through the STATS19 database were analyzed. Factors associated with pedestrian, driver, and environment were investigated using a novel approach that combines a classification and regression tree with random forest approach. Results: Significant severity predictors under fine weather conditions from the models included speed limits, pedestrian age, light conditions, and vehicle maneuver. Under adverse weather conditions, the significant predictors were pedestrian age, vehicle maneuver, and speed limit. Conclusions: Elderly pedestrians are associated with higher pedestrian injury severities. Higher speed limits increase pedestrian injury severity. Based on the research findings, recommendations are provided to improve pedestrian safety.

Towards a Safe and Efficient Motorway System: Literature Review on Variable Speed Limits

Variable speed limits (VSL) is an emerging ITS tool, which can help to improve safety and efficiency of motorway systems through a better harmonization of traffic flow. It can reduce variation in speed of vehicles travelling along the controlled section. The implementation of VSL encourages a uniform driving behaviour and thus resulting in a better distribution of traffic over the motorway network, and better utilization of the road infrastructure. The primary objective of motorway traffic management is to improve mobility benefits of motorways under acceptable safety standards; this is also the main purpose of applying VSL. This paper reviews the existing VSL methods from view points of safety and mobility gains or losses due to VSL on motorway systems. A systematic review of the literature of empirical as well as simulation-based studies is presented.