Ambra Toletti

Enhancing energy efficiency in railway operation through RCG-based rescheduling

This paper presents a new approach for train rescheduling, based on a Resource Conflict Graph (RCG) approach, which considers energy efficiency aspects into solutions. The model is expressly developed for highly congested mixed traffic networks, where rail operation deals with different rail services (Intercity, InterRegio; single wagonload, mail trains) and high computing speed is required. Here energy consumption is considered as a constraint, in order to improve algorithm performances and, at the same time, to obtain a more energy efficient solution. First experiments with real data of a Swiss network show how the model behaves with different energy consumption constraints and its suitability for real time applications.

Infrastructure and Operational Influences on Collisions Between Trams and Left-Turning Cars

This research identified infrastructural and operational factors that influenced the most common type of car–tram collision: cars making opposing turns in front of trams. Few studies have analyzed influences on car–tram collisions quantitatively, but none have explored predictor factors for opposing-turn crashes—a research gap addressed with this paper. The two largest Swiss tram networks, Basel and Zurich, were used for the analysis. A point-based research approach was chosen: all locations within a tram network at which a car could turn left (an opposing turn where traffic drives on the right) in front of a tram were identified. For each of these points, data on dependent and predictor variables were collected. This data set was analyzed with Poisson, negative binomial, and zero-inflated negative binomial regression models. The number of left-turning car–tram collisions was used as the dependent variable, while predictors were derived from a literature review; models were fitted by using all predictors and with forward variable selection by means of Akaike’s information criterion. Traffic volumes (cars and trams), tram speed, and dedicated left-turn lanes were found to be significantly associated with a higher frequency of car–tram collisions, whereas turning left to access a service rather than a road, left-turn restrictions, proximity to a tram stop, and perpendicular turning angles were significantly associated with a lower frequency of left-turning car–tram collisions. On the basis of these results, left turns across tramways should be restricted for cars. Remaining conflict points should be located close to tram stops, have limited tram speed, and feature perpendicular turning angles.

Energy savings in mixed rail traffic rescheduling: an RCG approach

This paper presents an enhanced version of the Resource Conflict Graph (RCG) approach for railway rescheduling that considers the reduction of tractive energy consumption in the rescheduling process. The objectives and constraints considered in freight train rescheduling are different from those related to passenger trains. For example, there is generally more flexibility in freight train scheduling regarding routes and departure/arrival times. On the other hand, freight trains have frequent unplanned stops for overtaking and acceleration phases use significant energy, especially for long freight trains. Therefore, energy consumption is recognized as an important cost factor in freight train operations and it is commonly used to help plan schedules. Energy consumption can be reduced by choosing energy efficient paths (less traffic, less gradient) and driving with speed profiles that improve route regularity (i.e., that avoid unplanned stops and minimize acceleration phases). The paper describes the proposed rescheduling approach and then applies it in a numerical example evaluated using the test track of the Railway Operations Lab located in the facilities of the Institute for Transport Planning and Systems (IVT) at ETH Zurich.