Miquel Estrada

Improving Bus Travel Times with Passive Traffic Signal Coordination

A simulation optimization model is outlined: traffic signal offsets in intersections are calculated to minimize the travel time of bus users in an urban network. The model considers a passive signal priority system and restricts the maximal incremental delay caused to car users. The simulation tool is able to trace discrete trajectories of both buses and cars in a network. It also evaluates potential perturbations that may cause time variations for average performance. Moreover, the optimization tool is based on evolutionary algorithms. The results of applying the traffic signal coordination model to a set of small trial networks are given. It is proved that the algorithm is able to design a sequence of signal offsets that reduces bus travel times by an 8.5% rate in a real network while maintaining the incremental car delay below 5%.

Large-scale microscopic simulation of taxi services. Berlin and Barcelona case studies

The paper presents research on large-scale microscopic simulation of taxi services in Berlin and Barcelona based on floating car data collected by local taxi fleets. Firstly, Berlin’s and Barcelona’s taxi markets are shortly described and the demand and supply data obtained from FCD analysed. Secondly, the online taxi dispatching problem formulation for this specific case is given, followed by the definition of two real-time rule-based heuristics used to dispatch taxis dynamically within the simulation. Finally, the simulation setup in MATSim is described, and the results obtained with both heuristics are analysed and compared in terms of dispatching performance, proving the effectiveness of the second strategy at different demand and supply scales. This paper is an extended version of Maciejewski and Bischoff 2015, where only the Berlin case study was presented.

Long-Haul Shipment Optimization for Less-Than-Truckload Carriers

Less-than-truckload (LTL) carriers supply freight transportation services for small parcel shipments. These companies consolidate multiple shipments in vehicles to guarantee the efficiency of the system. A method for LTL carriers is presented to solve the long-haul routing design problem with capacitated distribution centers and time-constrained shipments. The method uses direct, hub-and-spoke, and stopover strategies to allocate shipments in the set of routes. The resolution method is based on a tabu search algorithm. The search process in the solution domain is performed dynamically with four possible perturbations. The results obtained in a set of test problems demonstrate that the restart parameters play a significant role in the efficiency of the algorithm. Implementation of this computational technique in the long-haul operations network of the largest carrier in Spain reduced transportation costs by 6%.

Agent-Based Simulation Framework for the Taxi Sector Modeling

Abstract Taxi services account for a significant part of the daily trips in most cities around the world. These services are regulated by a central authority, which usually monitors the performance of the taxi services provision and defines the policies applied to the taxi sector. In order to support policy makers, fleet managers and individual taxi drivers, there is a need for developing models to understand the behavior of these markets. Most of the models developed for analyzing the taxi market are based on econometric measurements and do not account for the spatial distribution of both taxi demand and supply. Only few simulation models are able to better understand the operational characteristics of the taxi market. This paper presents a framework for the development of agent based taxi simulation models. It is aimed at assessing policy makers, taxi fleet managers and individual drivers in the definition of the optimum operation mode and the number of vehicles.

Optimal Length of Transit Network with Traffic Performance Microsimulation Application to Barcelona, Spain

This paper examines the design of high-performance transit networks that minimize transit agency costs, the time of transit users in the system, and the travel time of car users. Surface transit services need segregated lanes to achieve a target cruising speed so that the transit network length has a significant effect on traffic performance. This effect is modeled with the macroscopic fundamental diagram (MFD). The optimization proceeds in two steps. First, an analytic model defines the optimal layout of surface transit networks according to the time headway, stop spacing, line spacing, and network size variables. Then, the average travel time of the traffic network is evaluated with the MFD curve corresponding to the former transit network length. The full methodology has been implemented in the city of Barcelona, Spain. MFD was calibrated in the citys central district by means of traffic microsimulation runs. The social optimum for the number of corridors is 15, somewhat smaller than the optimization that does not consider traffic (23 corridors).

Effect of Variable Bus Speeds on Bus Network Design

This article provides a methodology for solving the bus network design problem, covering network design and frequency setting and taking into consideration that commercial speeds of buses vary depending on the aggregated frequency of buses on each corridor. This methodology, referred to as Variable Speed Methodology, uses a variation of an algorithm proposed by Baaj and Mahmassani that assumes speeds remain constant (denoted Fixed Speed Methodology). Both methodologies were applied to the street network of Barcelona. Outputs were compared, and it was found that the Variable Speed Methodology produces a bus network with faster average travel speeds, shorter travel times, smaller fleet size, less route kilometer, and fewer buses per link while still serving the same level of demand. These results demonstrate that taking variability of bus speeds into consideration when performing route generation and frequency setting can significantly improve the performance of the bus network produced.