DESIGN OF RIDE - HAILING SERVICES FOR LARGE - SCALE SYSTEMS

Today private vehicles in the cities is a high problem, due to the congestion they create, their pollution and their use of public space. Various alternatives exist, as public transportation and other modes, and still the part of people using cars remain too important. What makes the individual car so indispensable, and what alternative mode could replace them, assuring lower negative impact? The main advantage of the car is that it is the most convenient point-to-point mode: it can reach high speed and allows carrying voluminous or heavy personal equipment and multiple people. It is in our habits, and losing these features is hard to accept. It is especially the case for people that need to pick or drop somebody, carry luggage, shopping bags, or some furniture, or have to reach places where there is not any other alternative transport (as train or bus). In term of offered advantages, the closest alternative transport mode to the private car is the ride-sourcing service. Just as private vehicles, it allows point-to-point trips and has similar vehicle-related characteristics. However, ride-sourcing also presents some inconvenience, as the less trivial trip-organizing process, some inevitable waiting time, and the service cost. Still, there are some fields in which ride-sourcing could offer an important improvement – most of all it could rationalize and optimize vehicle’s use. In fact, cars can generally offer up to four passenger places and still mostly they are carrying only one person – the driver. Also, when the private vehicles aren’t driven, they occupy a lot of space on the streets, staying unused more then 90% of the time. A transfer from the private vehicle’s mode (PV) on the ride-sourcing service mode would surely reduce the number of vehicles in the streets. Also, this mode could be designed in a way that uses the ride-sharing potential, that would reduce the required number of vehicles. Gaining space on the streets and reducing the required number of vehicles could permit to reduce consequently city’s congestion and improve urbanistic aspects. There are already some Transport Network Companies (TNC) that offer similar services, as for example Uber Pool. However, the demand for these services isn’t high enough to evaluate their impact on the traffic. Also, the performance of such a service could most likely be related to the number of users, increasing the probability of ride-sharing trips. Various research have already been performed to put in evidence the positive effect of the ride-sourcing using ride-sharing systems (Santi, 2014), (Alonso-Mora, 2017). They show that ride-sharing is actually possible, can be performed in a dynamic model, and can be implemented in a manner that the additional waiting and travel times remain in the acceptable range for the passenger. However, these researches do not consider the speed variation, due to the city congestion. With the ride-sharing, TNC system should allow to reduce the effective number of vehicles, which should help to resolve the congestion, but in the same time, TNC system also involve additional operational travels during which vehicles do not transport anyone and still circulate on the streets. The congestion is a very important aspect that is also a huge problem for a lot of cities. For these reasons, it’s interesting to figure out what would be the ride-sourcing and ride-sharing implementing TNC mode’s impact on it. Also, such a mode could be subject to a dynamic controlling strategy to reduce vehicles’ number in high-congested areas, by smartly deploying them among various regions. This strategy is described in M. Ramezani’s (Ramezani, 2018) and N. Geroliminis’ works (Geroliminis, 2012). Building and testing a dynamic model with a described TNC mode would permit to evaluate the congestion-solving abilities of this type of system. However, creating an MFD based Dynamic Model would require knowing in advance some specific parameters that would realistically describe TNC vehicles’ behaviour. To estimate these parameters, as there are not enough existing data for this type of TNC, a Microscopic Simulation Model is necessary. The aim of this thesis is to design and build a Microscopic Simulation Model, that reproduces the described TNC vehicles behaviour. The goal is to obtain valuable insight on TNC mode’s effect on traffic and its characteristics permitting future parametrization of a Macroscopic Dynamic Model.

An optimization framework for exclusive bus lane allocation in large networks with dynamic congestion

Nikolaos Geroliminis, Anastasios Kouvelas, Dimitrios Tsitsokas

Road space distribution among multiple modes of transport in urban networks has attracted the interest of several researchers and policy planners. Traditionally, these problems are solved by ignoring operational and dynamic characteristics of multi-modal congestion due to the computational burden involved. Revealing the relation between road space share and global performance of the network can lead to more efficient transport system design. The introduction of dedicated bus lanes in some parts of the network has been proposed as a measure to allow high occupancy vehicles to travel through regions with high traffic load without long delays. In this way, the bus transit system operates more efficiently and is competitive to the private car option in terms of travel time. This effect can stimulate a significant mode shift from car to bus and help alleviate congestion by reducing the number of low occupancy vehicles. In this work we address the problem of optimal allocation of exclusive bus lanes in a multi-modal urban network of fixed total road infrastructure and passenger demand, with the aim of minimizing the total passenger hours travelled (PHT) for all travel modes, within a framework which is consistent with the dynamics of congestion. A queueing theory based traffic flow model with proper treatment of spillbacks and traffic signal settings, known as the Store-and-Forward (SaF) model, is extended to simulate the dynamics of congestion inside the network by keeping track of the queues inside all links over time. The SaF simulation model can be used to evaluate the performance of different allocation policies.

2019

Toward Sustainable Ridesourcing Services: A Simulation Study on the Effects of Congestion, Fleet Size, and Willingness to Share

Caio Vitor Beojone, Nikolaos Geroliminis

Human mobility in large cities is a complex dynamical system with high density of population, many transport modes to compete for limited available space and many operators that try to efficiently manage different parts of this system. New emerging modes of transportation such as ride-sourcing (known as Transportation Network Companies – TNCs) and on-demand services create additional opportunities, but also more complexity. It is imperative to understand how TNCs' operations can interfere in traffic conditions while replacing other transportation modes to seek improvements in urban mobility. Moreover, the matching process shall have a place and thus the impact of passengers' behavior too, in a ridesplitting scenario. Therefore, this paper aims to investigate the effect of expanding fleet sizes for TNCs, passengers with different willingness to share, and operational strategies over congestion conditions under a sustainable perspective. This investigation considered a simulated urban network with real demand data from taxis in a megacity and incorporated traffic conditions through a Macroscopic Fundamental Diagram (MFD). Results show that sharing (allowing passengers to share their ride and have many passengers willing to do so) by itself is not capable of decreasing VKT if there is no control to the fleet size. On the other hand, sharing decreases the number of vehicles needed to provide high coverage and service times. To reduce emissions (by reducing VKT), TNCs should change their modus operandi; in a way to avoid that their fleet cruises without a defined trip (passenger with origin and destination).

2020

Adaptive approaches for the improvement of public transport in Latin American Cities

Regina Witter

Apart from the best-practice cases where public administration has been able to manage the transit service network and implement a strong regulation system, in the majority of Latin American cities public urban transport is supplied by a great number of quasi-artisan operators in an almost deregulated context. The private providers secure an intense but essentially deficient and unbalanced supply. With the growth of the cities and thus, increasing trvel distances, the deficiency of the public transport system becomes more problematic, especially for the lower income groups living on the outskirts. Moreover, the extension of the service, supplied in an increasing number of small vehicles competing on the streets, effects the worsening of traffic congestion and pollution. These problems arise as soon as the public authorities are not able to regulate the transport industry, not to mention to provide an efficient transport system by themselves. The lack of technical skills to plan, regulate and control the services but also weak political motivation are the primary obstacles to solve the poblem. The political and social costs of major regulatory changes often discourage politicans empowered, looking for more vote effective activities and measures. In order to implement an efficient regulation system, a stepwise, adaptive procedure has to be applied, securing over years significant improvements and the maturing of the transport industry.

Elsevier2007