Javier Ortigosa

Analysis of Network Exit Functions for Various Urban Grid Network Configurations

Macroscopic networkwide traffic models have been used to study aggregate traffic behavior on urban networks and to design traffic control strategies. However, less attention has been given to their application in the study of street network design. This paper uses the network exit function (NEF) to analyze traffic performance on an abstract grid network of various street configurations. The NEF is an aggregate relationship between trip completion rate and the number of vehicles circulating in a network. Street configuration is a topic of interest in many cities, especially in the United States, where city planners are considering street network conversions. Three configurations are addressed here: two-way streets, two-way streets with prohibited left turns (TWL), and one-way streets. This work builds on previous studies by incorporating more realistic traffic dynamics with microsimulation software (VISSIM) with dynamic traffic assignment enabled to emulate better the behavior of real drivers. This work finds that NEFs of two-way networks generally are smaller than those of TWL and one-way networks because of reduced capacity at intersections. Comparison of TWL and one-way networks is more nuanced, as traffic performance on these networks depends on route choice. If vehicles are always routed through the path with the shortest travel time, TWL networks offer NEFs with higher trip completion rates; however, if vehicles spread themselves across multiple alternatives, one-way networks provide better results. TWL networks offer a better trade-off between distance traveled and capacity at intersections, and one-way networks offer more shortest-path routing choices between origin–destination pairs.

Analysis of one-way and two-way street configurations on urban grid networks

ABSTRACT In this paper, we study traffic behavior on three different street configurations: one-way streets, two-way streets, and two-way streets with prohibited left turns. This study is novel because it employs three assignment and simulation methods to evaluate the networks under different conditions: analytical formulations, a Static Traffic Assignment algorithm, and a microsimulation software with a Dynamic Traffic Assignment. In general, the study reveals that two-way networks provide the shortest distance traveled but they are severely penalized by restrictions in capacity at the intersections. One-way networks offer the longest travel distances but have intersections with very high capacity. They perform better in congested scenarios. Finally, two-way networks with prohibited left turns provide the best compromise between distance travelled and intersection capacity, making them suitable for many different scenarios. Their main weakness is the lack of route redundancy that can lead to large travel times when networks are congested.

Analysis of the 3D-vMFDs of the Urban Networks of Zurich and San Francisco

In this paper we are studying the trade-off of urban road space dedicated to cars and buses (or trams) in two cities: Zurich and San Francisco. We employ the three-dimensional vehicle Macroscopic Fundamental Diagrams (3D-vMFD) which consist of creating the MFDs for networks with different levels of public transport operations. Based on the 3D-vMFD, we analyze and evaluate network performances when the percentage of dedicated bus lanes varies in a city. Simulation results show that when there are more dedicated bus lanes, the performance of cars worsens and the transit performance improves.