Multi-criteria appraisal of multi-modal urban public transport systems

This study proposes a multi-criteria decision making (MCDM) modelling framework for the appraisal of multi-modal urban public transportation services. MCDM is commonly used to obtain choice alternatives that satisfy a range of performance indicators. The framework embraces both compensatory and non-compensatory approaches including lexicographic, Simple Additive Weighting (SAW), technique for order preference by similarity to the ideal solution (TOPSIS) and Concordance Analysis. These methods are applied on survey data collected through a questionnaire in Teheran, Iran. The survey encompassed passengers, operators and the wider community and inquired about the perceived attributes of three urban public transport modes: regular bus (RB), bus rapid transit (BRT) and rail rapid transit (RRT). The aforementioned MCDM techniques were applied to rank the performance of the three studied transit modes. The outputs of this study are instrumental in supporting planning decisions and prioritizing measures to improve public transport services.Transport and PlanningCivil Engineering and Geoscience

Comparison of On-Line Time-Delayed and Non-Time-Delayed Urban Traffic Control via Remote Gating

Recent studies demonstrated the efficiency of feedback-based gating control in mitigating congestion in urban networks by exploiting the notion of network fundamental diagram (NFD). The employed feedback regulator of proportional-integral(PI)-type targets an operating NFD point of maximum throughput to enhance the mobility in the urban road network during the peak period, under saturated traffic conditions. In previous studies, gating was applied directly at the border of the protected network (PN), i.e. the network part to be protected from over-saturation. In this work, the recently developed feedback-based gating concept is applied at junctions located further upstream of the PN. This induces a time-delay, which corresponds to the travel time needed for gated vehicles to approach the PN. The resulting extended feedback control problem can be also tackled by use of a PI-type regulator, albeit with different gain values compared to the case without time-delay. Detailed procedures regarding the appropriate design of related feedback regulators are provided. In addition, the developed feedback concept is shown to work properly with very long time-steps as well. A large part of the Chania, Greece, urban network, modelled in a microscopic simulation environment under realistic traffic conditions, is used as test-bed in this study. The reported results demonstrate a stable and efficient behaviour and improved mobility of the overall network in terms of mean speed and travel time.Transport & PlanningCivil Engineering and Geoscience

Using taxi GPS data for macroscopic traffic monitoring in large scale urban networks: Calibration and MFD derivation

A two-Fluid Model (TFM) of urban traffic provides the macroscopic description of traffic state. The TFMs parameters are hard to calibrate, particularly for the dynamic traffic conditions. This leads to the TFM often being used to compare the quality of service through the plot of stopping time versus trip time of the vehicles in the network. Recently, the taxi GPS data has been applied to predict the traffic condition at the network level. Despite the network-wide coverage of the taxi GPS probe data, the penetration rate of taxis in the network traffic is still a vital and challenging issue for traffic estimation purpose. It is necessary to estimate penetration rate of taxis by combining with other data sources. Here, we propose a novel approach to fill two gaps: TFM parameter calibration and the taxis penetration rate. This method stretches the description of TFM to a zone size. The method is applied to real Changsha city GPS data, calibrating the parameters. The macroscopic fundamental diagram of the large-scale city is derived. For the Changsha case, running speed is the super-linear power law of the fraction of running cars; the fraction of stopping time is nearly linear power law of density, which can be an alternative of the density. The proposed method enables the calibration of TFM parameters and macroscopic traffic monitoring at urban scale using only GPS data.Transport and Plannin

Lane changing and speed interaction on freeways: An analytical microscopic study

Understanding the influence of lane changing manoeuvre on the capacity, stability, and breakdown of traffic flows is a crucial issue. In a recent study, four distinct lane change strategies on freeways have been empirically found: (1) Speed Leading; (2) Speed Leading with Overtaking; (3) Lane Leading; (4) Traffic Leading. To the best of our knowledge, combining speed choice and lane preference is not currently considered in most driving behaviour models. The principal aim of this paper is to investigate the impact of the forenamed lane change strategies on freeway traffic operations. The developed strategy-based lane change model has been implemented in a microscopic simulation environment. The study revealed that different lane change strategies may have various impact on the lane flow distribution and consequently on the freeway capacity. It has been seen that an unbalanced distribution of flow on a multi-lane freeway may lead to reduction of capacity. In addition, it has been found that the lane change rate variates under different lane change strategies. The highest traffic stability has been observed under speed leading and speed leading with overtaking strategies.Transport and PlanningCivil Engineering and Geoscience

Combination of traffic-responsive and gating control in urban networks: Effective interactions

Recent findings regarding macroscopic relationships of urban traffic measures such as the Macroscopic or Network Fundamental Diagram (MFD or NFD) have led to the development of novel traffic control strategies that can be applied at a network-wide level. One pertinent example is perimeter flow control (also known as gating or metering), which limits the rate at which vehicles are allowed to enter an urban region. In general, these gating strategies seek to prevent a network from becoming congested and maximize network efficiency/productivity by maintaining an optimal accumulation of vehicles within the network. Several studies have found that NFDs are more well-defined (i.e., have less scatter and show better overall network performance) when adaptive traffic signals are installed that dynamically respond to local traffic conditions. A combined gating and adaptive traffic control scheme can leverage the more reproducible macroscopic traffic patterns achieved with adaptive signals to provide more robust and efficient gating control. The purpose of this paper is to explore the benefits of combining perimeter gating with locally adaptive traffic signals through micro-simulation of the Chania, Greece traffic network. Two adaptive traffic signal strategies are considered with the feedback-based gating strategy: (1) a simple volume-based strategy and (2) a modified version of the SCATS algorithm. The results of the combined gating/adaptive signal control scheme are compared to gating under fixed traffic signals and the implementation of adaptive signals only. Overall, the study finds that travel delays and congestion can be considerably reduced with the combined strategy. This is because the adaptive traffic signals allow the network to achieve higher network productivity while the gating control allows the network to maintain this higher efficiency for a longer period of time than if left uncontrolled. The results are promising for the implementation of perimeter gating strategies in practiceTransport and PlanningCivil Engineering and Geoscience

Examining perimeter gating control of urban traffic networkswith locally adaptive traffic signals

Traditionally, urban traffic is controlled by traffic lights. Recent findings of the Macroscopic or Network Fundamental Diagram (MFD or NFD) have led to the development of novel traffic control strategies that can be applied at a networkwide level. One pertinent example is perimeter flow control (also known as gating or metering), which limits the rate at which vehicles are allowed to enter an urban region. This paper studies to which extent a combination of adaptive traffic control and gating improves the traffic flow. To this end, combinations of gating and traffic signal timing tested implemented in a microsimulation. It is found that gating is much more effective than adaptive signal timing for high traffic loads. Adaptive signal timing can improve the network performance by increasing the maximum flow and increasing the critical accumulation, i.e. the number of vehicles inside a protected network for which the performance is maximized. The latter helps to reduce queuing outside the protected network.Transport and PlanningCivil Engineering and Geoscience

Urban network throughput optimization via model predictive control using the link transmission model

Developing practicable and efficient real-time signal control strategies for urban road networks is a major challenge with significant scientific and practical relevance. For the sake of practical feasibility, many urban traffic control strategies are based on simplified models. In this way, a trade-off can be made between controller accuracy, and (computational) complexity of the controller. However, designing a controller which operates efficiently with low computational time under different traffic conditions (i.e. under-saturated, saturated and over-saturated) remains a challenge. Several linear and quadratic model predictive control approaches are described in the literature to tackle this problem without considering the shock-wave dynamics of spill-back under over-saturated conditions. The principal contribution of this paper is the formulation of a linear model predictive controller that takes the shock-wave dynamics into account. This is realized by modeling the traffic dynamics in a link using the link transmission model. The performance of the proposed controller is compared with two other existing strategies. The total time spent by all the vehicles in the network and the computation time have been applied as performance indexes for the appraisal of the control strategies. Simulation results show that the control strategy proposed in this paper achieves better throughput under over-saturated conditions within comparable, low computation time.Transport & PlanningCivil Engineering and Geoscience

Strategy-Based Driving Behaviour on Freeways: Findings of Test-Drive and On-Line Survey Study

Freeways form an important part of the road network. Drivers’ behavior can be split in longitudinal (acceleration and deceleration) and lateral behavior (lane changing). The combination of these two behaviors on freeways play a key role in traffic operations. This paper tries to describe the driving behavior, emphasizing the relation between the lateral and longitudinal behavior. To this end, an experimental study based on a test-drive and on-line questionnaire has been carried out. For the test-drive, 34 participants drove a vehicle equipped with monitoring systems. Based on the test drives a survey was developed regarding driving behavior in specific situations. This survey was answered by 1258 drivers who were questioned using videos for specific and relevant situations. The results show that most people choose a speed first, and stick to that. Fewer people adapt a strategy of having a desired speed which might change when they are in a different lane to overtake, or a strategy to choose a desired lane, and tries to adapt speed. A small fraction of the respondents mentioned that they have neither a desired speed or a desired lane. Most people (80%) use the right lane if possible, and 80% will not overtake at the right. 70% may have a courtesy behavior when needed. The outcome of this study has shed some light on the naturalistic driving behavior on freeways under different situations. The findings of this work can be implemented in traffic simulation programs, which are able to delay with this scale of traffic behavior. Repeating this survey in international context will reveal differences between drivers in various countries.Transport and Plannin

Lane Change Behavior on Freeways: An Online Survey Using Video Clips

Freeways forman important part of the road network. Yet, driving behavior on freeways, in particular lane changes and the relation with the choice of speed, is not well understood. To overcome this, an online survey has been carried out. Drivers were shown video clips, and after each clip they had to indicate what they would do after the moment the video stopped. A total of 1258 Dutch respondents completed the survey. The results show thatmost people have a strategy to choose a speed first and stick to that, which is the first strategy. A second, less often chosen, strategy is to choose a desired lane and adapt the speed based on the chosen lane. A third strategy, slightly less frequently chosen, is that drivers have a desired speed, but contrary to the first strategy, they increase this speed when they are in a different lane overtaking another driver. A small fraction have neither a desired speed nor a desired lane. Of the respondents 80% use the right lane if possible, and 80% avoid overtaking at the right. Also 80% give way to merging traffic.The survey was validated by 25 survey respondents also driving an instrumented vehicle. The strategies in this drive were similar to those in the survey. The findings of this work can be implemented in traffic simulation models, e.g., to determine road capacity and constraints in geometric design.Transport and PlanningTransport and Plannin