Microscopic Simulation Approach Research Articles

Effect of dynamic route guidance on urban traffic network under Connected Vehicle environment


 
 
 Although Connected Vehicle technology is developing rapidly, connected vehicles (CV) are going to mix with the traditional vehicles (i.e., non-connected vehicles) for a long time. The effects of deploying CV on urban traffic systems are actually not clear. The main objective of this study is to evaluate the potential effects of route guidance under connected vehicle environment on an urban traffic network in terms of traffic mobility and safety. Microscopic simulation approach is used to conduct CV environment simulation and the rolling horizon approach is used for information updating among the connected vehicles. Meanwhile, driving behavior is modeled through aggressiveness and awareness of drivers. Traffic mobility for the road network was measured by average trip time and average vehicle trip speed. A surrogate measure, i.e., the time-to-collision involved incident rate for one kilometer driven, was used to assess the safety of the road network. Based on a real urban traffic network, the impacts of market penetration levels of connected vehicles and information updating intervals were studied. Simulation results showed that market penetration level of connected vehicles has little impact on the mobility and safety of road network. In addition, according to the simulation conducted in this paper, shorter updating interval is shown to be likely to lead to better mobility, while the safety of road network is likely to decline, under the assumptions embraced in the simulation. By contrast, the simulation also showed that longer updating interval is likely to lead to better safety and decreased mobility.
 
 

Assessing the impact of converting roundabouts to traffic signals on vehicle emissions along an urban arterial corridor in Qatar

ABSTRACTThe type of control at intersections has a major effect on the operation of any urban corridor. Different predefined procedures are available to calculate some of the main operational characteristics, such as capacity, delay, and level of service, in order to select the best type of control. However, there are other important factors that affect major arterials operational characteristics, factors that are not fully addressed, such as the impact of emissions. In this study, a microscopic simulation approach using VISSIM and MOVES was developed to assess the environmental effect of converting four three-lane roundabouts to signalized intersections along a heavily congested urban corridor in Qatar. A decision was made to switch all roundabouts to traffic signals for better operations. Preliminary results indicated that the signal control outperformed the roundabout in the range of 37% to 43% reduction in emissions. A more detailed analysis revealed that roundabout corridor operations’ effects on emission rates are divergent from those of signalized corridors, particularly upstream and downstream of the intersections. Immediate roundabout upstream approaches are driver behavior dependent, characterized by substantial coasting at lower speeds and subsequent re-accelerating with less idling, described as acceleration events, which resulted in high emission rates, while signalized corridors are signal timing dependent, characterized by ample idling with less coasting and re-acceleration, resulting in reduced emission rates. The results also revealed that there was no significant difference between emission rates in the vicinity of the two types of control. Both recorded nearly the same emission rate.Implications: A microscopic simulation approach using VISSIM and MOVES was developed to assess the environmental effect of converting four three-lane roundabouts to signalized intersections along a heavily congested urban corridor in Doha, Qatar. Intersection geometries along with the control type have significant impact on emission rates and play a major role in assessing environmental impacts. US EPA MOVES was calibrated to Qatar conditions which can be used to estimate emission factors and quantify vehicular emissions along other corridors in the country. The results can also be beneficial for other countries within the region.

Avalanche breakdown evolution under hot-carrier stress: a new microscopic simulation approach applied to a vertical power MOSFET

During avalanche breakdown, hot carriers are generated due to impact ionization. In a MOSFET, some of these hot carriers impinge on the field oxide and can be captured in the oxide. Over time, this leads to an accumulation of fixed charges at the Si/SiO $$_2$$ interface and consequently to a degradation of device characteristics. Among those characteristics, the drift of the avalanche breakdown voltage is one of the most important aspects of device reliability. In this study, we present the first microscopic simulation of the oxide charge generation due to hot carriers and their field-driven recombination under avalanche breakdown conditions in a vertical power MOSFET. The distribution functions of electrons and holes in the device are calculated by solving their coupled Boltzmann equations. Based on the hot-carrier distribution functions, the injection rates of hot electrons and holes into the field oxide are evaluated. The resulting drift of the avalanche breakdown voltage in this simulation is in good agreement with experimental results. The underlying device internal processes are discussed, and the gained insight might help to improve the reliability of power transistors.

Transit signal priority accommodating conflicting requests under Connected Vehicles technology

In this research, a person-delay-based optimization method is proposed for an intelligent Transit Signal Priority (TSP) logic that resolves multiple conflicting TSP requests at an isolated intersection. This TSP with Connected Vehicles accommodating Conflicting Requests (TSPCV-CR) overcomes the challenge bore by the conventional “first come first serve” strategy and presents significant improvement on bus service performance. The feature of TSPCV-CR includes green time re-allocation, simultaneous multiple buses accommodation, and signal-transit coordination. These features help maximize the transit TSP service rate and minimize adverse effect on competing travel directions. The TSPCV-CR is also designed to be conditional. That is, TSP is granted only when the bus is behind schedule and the grant of TSP causes no extra total person delay. The optimization is formulated as a Binary Mixed Integer Linear Program (BMILP) which is solved by standard branch-and-bound routine. Minimizing per person delay is the objective of the optimization model.The logic developed in this research is evaluated using both analytical and microscopic traffic simulation approaches. Both analytical tests and simulation evaluations compared three scenarios: without TSP (NTSP), conventional TSP (CTSP), and TSP with Connected Vehicles that resolves Conflicting Requests (TSPCV-CR). The measures of effectiveness used include bus delay and total travel time of all travelers. The performance of TSPCV-CR is compared against conventional TSP (CTSP) under four congestion levels and three different conflicting scenarios. The results show that the TSPCV-CR greatly reduces bus delay at signalized intersection for all congestion levels and conflicting scenarios considered. Simulation based evaluation results show that the TSPCV-CR logic reduces average bus delay between 5% and 48% compared to the conventional TSP. The range of improvement corresponding to the four different v/c ratios tested, which are 0.5, 0.7, 0.9 and 1.0, respectively. No statistically significant negative effects are observed.

Coordinated transit signal priority supporting transit progression under Connected Vehicle Technology

In this paper, a person-delay-based optimization method is proposed for an intelligent TSP logic that enables bus/signal cooperation and coordination among consecutive signals under the Connected Vehicle environment. This TSP logic, called TSPCV-C, provides a method to secure the mobility benefit generated by the intelligent TSP logic along a corridor so that the bus delay saved at an upstream intersection is not wasted at downstream intersections. The problem is formulated as a Binary Mixed Integer Linear Program (BMILP) which is solved by standard branch-and-bound method. Minimizing per person delay has been adopted as the criterion for the model. The TSPCV-C is also designed to be conditional. That is, TSP is granted only when the bus is behind schedule and the grant of TSP causes no extra total person delay.The logic developed in this research is evaluated using both analytical and microscopic traffic simulation approaches. Both analytical tests and simulation evaluations compared four scenarios: without TSP (NTSP), conventional TSP (CTSP), TSP with Connected Vehicle (TSPCV), and Coordinated TSP with Connected Vehicle (TSPCV-C). The measures of effectiveness used include bus delay and total travel time of all travelers. The performance of TSPCV-C is compared against conventional TSP (CTSP) under four congestion levels and five intersection spacing cases. The results show that the TSPCV-C greatly reduces bus delay at signalized intersection for all congestion levels and spacing cases considered. Although the TSPCV is not as efficient as TSPCV-C, it still demonstrates sizable improvement over CTSP. An analysis on the intersection spacing cases reveals that, as long as the intersections are not too closely spaced, TSPCV can produce a delay reduction up to 59%. Nevertheless, the mechanism of TSPCV-C is recommended for intersections that are spaced less than 0.5 mile away. Simulation based evaluation results show that the TSPCV-C logic reduces the bus delay between 55% and 75% compared to the conventional TSP. The range of improvement corresponding to the four different v/c ratios tested, which are 0.5, 0.7, 0.9 and 1.0, respectively. No statistically significant negative effects are observed except when the v/c ratio equals 1.0.

The impact of random mid-block pedestrian crossing on urban arterial operational characteristics in developing countries

Highway Capacity Manual, 2010 (HCM) has developed an integrated multimodal approach to evaluate the quality of service along urban streets. This approach emphasises four different transportation modes, automobile, pedestrian, transit and bicycle. Although HCM procedures are widely used for capacity and level of service analysis, there are several factors that are not comprehensively addressed, such as the effect of pedestrians' mid-block crossing. In this paper, a multimodal microscopic simulation approach is used to address the significance of random mid-block crossing on the operational characteristics of urban arterials in developing countries. The a major urban arterial corridor that experiences high pedestrians volume and vehicular traffic is studied. VISSIM microscopic simulation environment is calibrated based on traffic and speed studies, and three different pedestrians' crossing cases are evaluated. Simulation results have shown that the scenario when pedestrians are randomly crossing the study corridor is associated with lower operational traffic conditions.

Crash risk evaluation of aggressive driving on motorways: Microscopic traffic simulation approach

This paper provides quantitative evaluation of safety implications of aggressive driving (speeding, following closely and weaving through traffic) by using microscopic traffic simulation approach. Combination of VISSIM and Surrogate Safety Assessment Model (SSAM) were used to model motorway and assess safety of the simulated vehicle. The use of vehicle conflicts was validated by correlating it to historic crashes. Crash risk, severity levels and the magnitude of the perceived benefits of aggressive driving were quantified relative to normal drivers under two scenarios: (1) congested, and (2) non-congested traffic conditions. Involvement in vehicle conflicts is used to determine crash-risk while reductions in Post Encroachment Time (PET) and travel time were used to determine the severity levels of the expected crashes and the magnitude of the perceived benefits. The results indicated that the crash risk of aggressive drivers was found to be in the range 3.10–5.8 depending on traffic conditions and type of road aggression. PET of the conflicts involving aggressive drivers reduced by 7–61% indicating high severity levels of the expected crashes. Moreover, the magnitude of the perceived benefit in terms of reduction in travel time was found to be as little as 1–2%. The study concluded that aggressive driving is entailed with a massive risk while its benefits are actually very little.

Transit Signal Priority with Connected Vehicle Technology

Transit signal priority (TSP) has been studied as a control strategy that offers preference to transit vehicles at signalized intersections. Although TSP has been deployed in many places, several shortcomings, such as adverse effect on side streets and uncertainty about the benefit, have been identified. Therefore, a new TSP logic proposed to overcome these shortcomings takes advantage of the resources provided by connected vehicle technology, including two-way communications between buses and the traffic signal controller, accurate bus location detection and prediction, and number of passengers. The key feature of the proposed TSP logic is green time reallocation, which moves green time instead of adding extra green time. TSP is also designed to be conditional. That is, delay per person is used as the most important criterion in deciding whether TSP is to be granted. The logic developed in this research was evaluated in two ways: with analytical and microscopic simulation approaches. In each evaluation, the proposed TSP was compared with two scenarios: no TSP and conventional TSP. The analysis used bus delay and per person delay of all travelers as measures of effectiveness. The simulation-based evaluation results showed that the proposed TSP logic reduced bus delay between 9% and 84% compared with conventional TSP and between 36% and 88% compared with the no-TSP condition. The range of improvement corresponding to four volume-to-capacity ratios was tested. No significant negative effects were caused by the proposed TSP logic.

Modeling emergency evacuation of individuals with disabilities (exitus): An agent-based public decision support system

In this paper, we present a public decision support system (DSS) distinguished from various DSSs in the private business sector in terms of its ownership, data scarcity, and beneficiaries. In particular, our system is intended to play a vital role in assessing and optimizing emergency response plans for rare but catastrophic events such as the September 11th attacks. While taking an agent-based microscopic simulation approach in a hierarchical framework, we used our model to estimate the effectiveness of alternative evacuation strategies to support emergency response planning as a part of business continuity planning for all private business organizations. The presented model is unique because it considers individuals with disabilities explicitly in terms of speed, ability to negotiate the environment, and normalcy bias depending on type of disability. It is also capable of classifying the environment in terms of accessibility characteristics encompassing various conditions which have been shown to have a disproportionate effect upon the behavior of individuals with disabilities during an emergency.Through a series of simulation experiments, our system identified specific locations (e.g., the NW landing) on the 3rd floor of the test bed building as possible bottleneck spots under certain conditions (e.g., the sharp increase in individuals with disabilities among residents). This way, our system provides the architect with tools to test the structure’s design to determine how well it meets the identified requirements for emergency evacuation to accommodate this shifting demographic. In particular, our system strongly demonstrated the effectiveness of new emergency evacuation strategies for individuals with disabilities such as assisted evacuations which allows other healthy people to play more active roles compared to traditional strategies in which individuals with disabilities are helplessly waiting for assistants such as fire fighters at the designated area. Our system also revealed that people using wheelchairs and those with lower stamina were at the greatest risk. People with lower stamina such as the elderly, people with chronic health conditions, or those with temporary injuries are at a greater risk mainly because they are not easily identifiable. Ultimately, the proposed DSS system can be used to inform public policy professionals of more effective, evidence-based evacuation planning and environmental design methods based on a better understanding of the behavior of individuals with disabilities.

Income-contingent user preferences in policy evaluation: application and discussion based on multi-agent transport simulations

Standard economic policy evaluation allows the realization of projects if the aggregated economic benefit outweighs their costs. The use of one single aggregated welfare measure for evaluating and ranking projects has often been criticized for many reasons. A major issue is that differentiated effects on individuals or subgroups of the population are not taken into consideration. This leads to the need for transport planning tools that provide additional information for politicians and decision makers. The microscopic multi-agent simulation approach presented in this paper is capable of helping to design better solutions in such situations. In particular, it is shown that the inclusion of individual income in utility calculations allows a better understanding of problems linked to public acceptance. First, individual income-contingent utility functions are estimated based on survey data in order to describe human mobility behavior. Subsequently, using the MATSim framework, the implementation is tested in a test scenario. Furthermore, and going beyond Franklin (2006), it is shown that the approach works in a large-scale real world example. Based on a hypothetical speed increase of public transit, effects on the welfare distribution of the population are discussed. It is shown that the identification of winners and losers seems to be quite robust. However, results indicate that a conversion or aggregation of individual utility changes for welfare analysis is highly dependent on the functional form of the utility functions as well as on the choice of the aggregation procedure.

Microscopic Traffic Simulation Approach to the Capacity Impact Analysis of Weaving Sections for the Exclusive Bus Lanes on an Urban Expressway

This paper presents a microscopic traffic simulation approach to the capacity impact analysis of weaving sections caused by the installation of exclusive bus lanes (XBLs) on urban expressways. Three typical configurations of XBL in Beijing are identified, including median bus lane with off-on-ramp, curbside bus lane with on-off-ramp, and curbside bus lane with off-on-ramp. Then, the weaving section length, headway, mainline volume, as well as off-ramp and on-ramp volumes for general traffic are considered as parameters in designing simulation scenarios. Finally, the microscopic simulation is executed, by which the capacity of general traffic for weaving sections is estimated and the impact of the weaving section length and headway on the capacity is evaluated. It is found that the weaving section length and headway have different impacts on the capacity of general traffic in different configurations. The results also provide that the weaving section length and headway are more sensitive in the on-off-ramp than in the off-on-ramp scenario with the curb bus lane.

Evaluation of travel demand strategies: a microscopic traffic simulation approach

This research investigates the design and impact of a new travel demand management approach, namely the Downtown Space Reservation System (DSRS), using a microscopic traffic simulation approach executed in VISSIM. The DSRS is part of a Travel Demand Management strategy that is designed to mitigate traffic congestion in a downtown urban setting. The simulation is conducted according to an experimental design procedure for a revised road network representing downtown Boise, Idaho. The issues that are tested in the simulation include: (1) whether the DSRS improves traffic performance when compared with the case without the DSRS; (2) how the DSRS performs compared with a reservation system that uses a First Come First Serve principle; and (3) how the specific DSRS parameters (such as, the relative importance of throughput versus revenue generation) influence network system performance. Conclusions and future research recommendations are provided based on the insights from the simulation modeling work.

Policy Evaluation in Multiagent Transport Simulations

In democratically organized societies, the implementation of measures with regressive effects on welfare distribution tends to be complicated because of low public acceptance. The microscopic multiagent simulation approach presented in this paper can help to design better solutions in such situations. Income can be included in utility calculations for a better understanding of problems linked to acceptability. This paper shows how the approach can be used in policy evaluation when income is included in user preferences. With the MATSim framework, the implementation is tested in a simple scenario. Furthermore the approach works in a large-scale, real-world example. On the basis of a hypothetical price and speed increase of public transit, effects on the welfare distribution of the population are discussed. This approach, in contrast with applied economic policy analysis, allows choice modeling and economic evaluation to be realized consistently.

Safety Implications of Mandated Truck Speed Limiters on Freeways

This paper presents the results of a study funded by Transport Canada to investigate the safety implications of mandated truck speed limiters. The study adopted a microscopic simulation approach that was applied to a number of maximum speed control strategies, including 105 km/h. The sensitivity of safety performance with respect to changes in geometric and traffic scenarios was investigated. The study found that truck speed limiters produced positive safety gains for different assumed volumes and percentages of trucks and different compliance levels. Under certain conditions, such as high volumes and high percentage of trucks, speed limiters produced a reduction in safety.

Noise emissions at intersections: comparing microscopic and macroscopic traffic simulation approaches

Environmental noise mapping often involves the use of traffic simulation software. In most cases, traffic flows are simulated in a macroscopic way, considering only traffic flow parameters averaged over road segments. This approach does not allow to correctly account for the typical deceleration and acceleration patterns of traffic at intersections, which influence local noise emissions. Microscopic traffic simulation models, which model each vehicle individually, incorporate these dynamic effects. However, they require much larger amounts of input data for calibration, and are therefore less suited to map large areas. In this paper, we investigate the possible influence of the choice of simulation detail on simulated traffic flow parameters and, as a consequence, on noise emissions near intersections. As a case study, several types of road intersections under various traffic demand and traffic composition conditions are considered. Simulation results are obtained using a microscopic (Paramics) as well as a mesoscopic (MaDAM) and a macroscopic (OmniTRANS) traffic simulation model, and predicted traffic flow parameters and noise emission values are compared between these approaches.

Forecasting Travel Supply and Demand by Modeling Multiscale Urban Environments

Traditional microscopic transport simulation approaches usually separate the supply from the demand forecasting by modeling travel demand and the transportation network separately. This approach generally leads to a sizeable calibration task, especially when nested multiscale simulations must be conducted. A generic approach is proposed to model a virtual urban environment in a way that combines data about the population, transportation network, and locations. A scale-independent approach for modeling such an urban environment is presented, along with its application to the Quebec City, Canada, metropolitan region. Some initial results from the TransNetSIM mesoscopic simulator and some computational challenges that were addressed are presented and discussed.

Microscopic Simulation Approach to Effectiveness Analysis of Transit Signal Priority for Bus Rapid Transit

Transit signal priority (TSP) is one of the critical components of bus rapid transit (BRT) and a key technology in enhancing its operational efficacy. It not only provides priority to the BRT vehicle but also manages the trade-off between the delay of buses at an intersection and the impacts on other traffic. This paper focuses on the design and evaluation of a simulation of signal priority for BRT under mixed traffic flow conditions. Taking the Southern Axis BRT Line 1 in Beijing as a case study, different signal priority strategies, including green extension, red truncation, and special phase insertion, are developed for the signalized intersection along the BRT route. A signal coordination plan is designed for the section composed of four intersections in the BRT system. The study uses the VISSIM microscopic traffic simulation model to analyze the impacts of traffic parameters, especially those of nonmotorized traffic, on the effectiveness of TSP along the corridor. Simulation results indicated that the BRT vehicles would typically benefit from transit priority with travel times savings and delay reduction, as well as greater schedule adherence, and suggest that these benefits may be obtained with little negative impacts to the overall system. The results also indicated that the volume of nonmotorized traffic is one of the most important factors that influence the effectiveness of TSP implementation in a mixed traffic flow.

Simulation and dynamics of freeway traffic

This paper presents the new package entitled Simulator of Intelligent Transportation Systems (SITS) and a computational oriented analysis of traffic dynamics. The SITS adopts a microscopic simulation approach to reproduce real traffic conditions considering different types of vehicles, drivers and roads. A set of experiments with the SITS reveal the dynamic phenomena exhibited by this kind of system. For this purpose a modelling formalism is developed that embeds the statistics and the Laplace transform. The results make possible the adoption of classical system theory tools and point out that it is possible to study traffic systems taking advantage of the knowledge gathered with automatic control algorithms. A complementary perspective for the analysis of the traffic flow is also quantified through the entropy measure.

Dynamical Analysis of Freeway Traffic

This work presents the simulator of intelligent transportation systems (SITS). The SITS is based on a microscopic simulation approach to reproduce real traffic conditions in an urban or nonurban network and considers different types of vehicles, drivers, and roads. A dynamical analysis of several traffic phenomena is then addressed. The results of using classical system theory tools notes that it is possible to study traffic systems, taking advantage of the knowledge gathered with automatic control algorithms. In this line of thought, a new modeling formalism based on the embedding of statistics and Fourier transform is also presented.

Combined continuous–microscopic modeling of laser plume expansion

A hybrid model is developed to study the dynamics of laser plume expansion in vacuum or into a background gas. The method takes advantages of both continuous and microscopic simulation approaches. As a result of the combination of two different numerical methods, such as, large particles and direct Monte Carlo simulation, the model describes high-rate laser ablation for a wide range of background pressures (from zero to hundreds Pa). The model is used to investigate laser plume interaction with background gases. Particularly, the plume–gas mixing and energy exchange are taken into account. The dynamics of the laser plume expansion is investigated. Snowplow effect is observed at sufficiently high pressures. At smaller pressures, strong plume–gas mixing takes place near the contact surface. The simulation results explain experimentally obtained spatial maps of the reaction products formed during the plume expansion into a reactive background gas.