Platoon Arrival Research Articles

Urban Platooning Combined with Dynamic Traffic Lights

Platooning is generally known as a control method for driving a group of connected and automated vehicles in motorway context. Nevertheless, platoon control might also work on urban roads. One possible strategy to increase overall road traffic performance and to reduce congestion in urban traffic networks is to combine platooning with traffic signal control at intersections. The traffic flow can be maximized with coordinated scheduling of traffic signals together with platooning activities, resulting in decreased travel times and fuel consumption. This paper investigates several aspects of this combined control, such as the procedures for coordination and communication between platooning vehicles and traffic signals. Efficient algorithms are suggested to optimize platoon formation and dissolution at junctions and to change traffic signal phases depending on platoon arrival and departure times. The proposed solutions have been tested and verified with SUMO, a high-fidelity microscopic traffic simulator.

A Platoon-Based Adaptive Signal Control Method with Connected Vehicle Technology.

One important objective of urban traffic signal control is to reduce individual delay and improve safety for travelers in both private car and public bus transit. To achieve signal control optimization from the perspective of all users, this paper proposes a platoon-based adaptive signal control (PASC) strategy to provide multimodal signal control based on the online connected vehicle (CV) information. By introducing unified phase precedence constraints, PASC strategy is not restricted by fixed cycle length and offsets. A mixed-integer linear programming (MILP) model is proposed to optimize signal timings in a real-time manner, with platoon arrival and discharge dynamics at stop line modeled as constraints. Based on the individual passenger occupancy, the objective function aims at minimizing total personal delay for both buses and automobiles. With the communication between signals, PASC achieves to provide implicit coordination for the signalized arterials. Simulation results by VISSIM microsimulation indicate that PASC model successfully reduces around 40% bus passenger delay and 10% automobile delay, respectively, compared with signal timings optimized by SYNCHRO. Results from sensitivity analysis demonstrate that the model performance is not sensitive to the number fluctuation of bus passengers, and the requested CV penetration rate range is around 20% for the implementation.

Probability of Capacity Enhancement and Disruption for Freeway Ramp Controls

Models based on gap-acceptance and queuing theory are proposed to model the effect of ramp controls on freeway operations. The models were developed for three types of patterns in ramp control and traffic flow: the uniform arrival with ramp metering, the random arrival without ramp metering, and the platoon arrival without ramp metering but with an upstream signalized intersection. From the theoretical point of view, the models were applied to address freeway ramp metering thresholds and the corresponding disruption probability. Studies have shown that ramp metering has been effective in reducing vehicle delays only when the rate of freeway traffic flow has reached a certain level of flow threshold. When freeway traffic is low, there are enough gaps in the freeway flow to accommodate the ramp flow, even when ramp traffic enters the freeway in platoons. The presented models accounted for the effect of platoon size that resulted from the three ramp controls and arrival flow patterns. Study results clearly indicate that more significant disruption on freeway operations occurs as a result of large platoon arrivals caused by an upstream traffic signal, than as a result of traffic that arrives randomly or uniformly. The models were also applied to provide quantitative assessments from the perspectives of freeway capacity. The results indicate that ramp metering produces increased freeway capacity and decreased disruption probability.

Calibration of Platoon Dispersion Model with High-Resolution Signal Event Data

This paper presents a scalable methodology for automatically measuring platoon characteristics on links between signalized intersections. This methodology estimates the parameters of the Robertson dispersion model that characterize platoon travel time and platoon distribution along a link. The Kolmogorov–Smirnov statistical test was used to assess how well the model parameters characterize the platoon arrivals measured by the high-resolution event data. The methodology was tested on a corridor of nine intersections containing 18 coordinated links with data that were collected over a 3-week period. Quite consistent results were obtained for link travel times; however, in many cases the observed link travel times were faster or slower than the posted speed. The distributions of the dispersion parameter showed considerable variation across the analysis period as well as across the system. The test corridor presented an interesting situation in which shorter links experienced greater dispersion than did longer ones. The results suggest that platoon dispersion is more sensitive to driver behavior characteristics related to roadside environment than to distance traveled along a street. The methodology could provide a means of prioritizing links for coordination and for self-calibrating traffic optimization models and adaptive control systems. The scheme could be integrated easily into modern signal controllers with high-resolution event logging capabilities.

Effect of signal coordination on traffic emission

This study investigates the effect of traffic signal coordination on emissions and compares it with their effects on operational performance measures of delay and stops. Various platoon ratios are obtained by simulating cycle lengths and offsets. Our results indicate that the impact of the cycle length on delay is more significant than those on stops and emissions for under-saturation traffic conditions. Given a fixed cycle length, increasing the platoon ratio can reduce delay, stops, and emissions, with reduction in emissions being correlated with stops than delay. The effect on emissions from the platoon arrival with respect to the onset of green or red indication is identified. With the same cycle length and platoon ratio, the early arrival situation, when the leading vehicles of a platoon encounters the red signal, can generate more emissions than are associated with late platoon arrival, when the last few vehicles in a platoon are stopped at the intersection by the onset of the red signal.

Goodput Analysis Using Terminating MAP for a Class of Discrete-Time Queueing Models

We develop an approach for computing the goodput using the idea of terminating Markovian Arrival Process (tMAP) for a finite queueing system in discrete-time with Platoon Arrival Process (PAP). A platoon is said to have been successfully transmitted if all of its packets have been admitted into the queue without any loss. Otherwise, the transmitted packets from the unsuccessful platoon would constitute wasted work. The throughput rate of the non-wasted work is called “goodput.” We apply the idea to modeling a queueing system with packet discarding policies in high speed networks—a system of considerable interest in networking.

Analysis of Platoon Impacts on Left-Turn Delay at Unsignalized Intersections

This research aimed to develop a methodology for analyzing the platoon impacts on major-street left-turn (MSLT) delay at two-way stop-controlled intersections. The main idea was to use a microscopic simulation tool to simulate different platoon scenarios in opposing through traffic and then to apply regression models to capture the impacts of platoons on the delay of MSLT. Two platoon variables were adopted as a simplification of the complex platoon scenarios to make analysis of the platoon effects on MSLT delay practical. The first two steps were to build simulation models for real-world unsignalized intersections and simulate scenarios with a combination of various factors related to platoons in VISSIM simulation. The models were calibrated with field data before simulation started. The next step was to define, derive, and calibrate two platoon variables for describing the duration and intensity of platoon arrivals in the opposing through traffic. This process effectively simplified the large combination of various factors. Finally, the two platoon variables and their relationship with the change factor of MSLT delay were modeled with regression tools. A relationship between the two variables and the delay change factor was established. The relationship indicated a positive effect by upstream platoons on MSLT delay and made it possible to quantify the impacts. The findings in this research could be used for research on platoon or signal impacts on left-turn treatments.

Development and Validation of Arrival-Based Uniform Delay Models for Oversaturated Signalized Intersections

This paper developed new uniform delay models for multiregime oversaturated traffic conditions at signalized intersection. Separate models were developed for each AT and then general models were obtained. The models directly consider the signal coordination (platoon arrival) effects, and thus eliminate the need to apply progression adjustment factors. The models were validated by comparing the control delays obtained from proposed models to the simulated delays from calibrated CORSIM simulation software. The control delays from the proposed delay models were not significantly different from the simulated field data for 93% of the conditions (52 scenarios out of 56). In contrast, when the HCM delay values were compared to the simulated field data, HCM estimates were not significantly different from the simulated field data only for 48% of the conditions (25 scenarios out of 56) Thus, the proposed models yield results that are comparable to field data, and the accuracy gained is worth the additional effort in computing delay.

Development and Field Testing of Platoon Identification and Accommodation System

This paper describes the development and initial field testing of an intelligent traffic control system for identifying and progressing platoons at isolated traffic signals on signalized arterials. This system uses advance detection to obtain real-time information about the presence and speeds of individual vehicles. Its algorithm identifies whether a platoon—of a userspecified minimum size and density—is approaching the signal and estimates platoon arrival time at the stop bar. When warranted, the system issues a low-priority preemption signal to progress the detected platoon. Duration of the initial preemption signal is based on estimated arrival and departure times for the smallest acceptable platoon and the estimated time needed to clear any queues present at the signal. Then, the system switches to an extension mode and provides progression to any additional vehicles determined to be in the platoon. It accomplishes that by increasing preemption time until no more vehicles are determined to be in the ...

Development and Field Testing of Platoon Identification and Accommodation System

This paper describes the development and initial field testing of an intelligent traffic control system for identifying and progressing platoons at isolated traffic signals on signalized arterials. This system uses advance detection to obtain real-time information about the presence and speeds of individual vehicles. Its algorithm identifies whether a platoon—of a user-specified minimum size and density—is approaching the signal and estimates platoon arrival time at the stop bar. When warranted, the system issues a low-priority preemption signal to progress the detected platoon. Duration of the initial preemption signal is based on estimated arrival and departure times for the smallest acceptable platoon and the estimated time needed to clear any queues present at the signal. Then, the system switches to an extension mode and provides progression to any additional vehicles determined to be in the platoon. It accomplishes that by increasing preemption time until no more vehicles are determined to be in the platoon or until the max timer expires. The system also ensures that the last progressed vehicle is not trapped in its dilemma zone. The platoon identification and accommodation system can be implemented by retrofitting existing National Electrical Manufacturers Association cabinets.

Simulation-Based Study of Traffic Operational Characteristics at All-Way-Stop-Controlled Intersections

Traffic operational characteristics at all-way-stop-controlled intersections were investigated by using AWSIM, a microscopic simulation model. The effects of vehicle arrival distribution and traffic volume split on intersection operations were studied. Traffic operations were analyzed from delay, capacity, and queue length perspectives. Empirical models were developed on the basis of simulation results for delay and queue length estimations. It was found that longer delays and queues resulted from platoon arrivals. Higher intersection capacity or lower control delay can be achieved with even volume splits on all the approaches. A generalized form of the delay model showed a better correlation compared with those for exponential-form models used by other studies. A nonlinear relationship was found to exist between the 95th percentile queue length and the average queue length. An empirical model was developed on the basis of the simulation results for estimation of the 95th percentile queue lengths. The model proves to be reliable and easy to use on the basis of field studies, and it fulfills one of the major shortcomings in queue estimation, which is currently unavailable in the Highway Capacity Manual.

Progression Adjustment Factors for Uniform Delay at Signalized Intersections

Signal progression plays an important role in controlling arrival pattern and delay at coordinated signalized intersections. In the Highway Capacity Manual (HCM), one random and five nonrandom arrival types are identified. The delays for nonrandom arrival cases (platoon arrivals) are computed by applying progression adjustment factors (PFs) to the delay for the random arrival case. However, HCM-estimated delays are found to be significantly different from field-measured delays for Arrival Types 1, 4, and 6. For Arrival Type 2 the HCM estimations are acceptable, although the deviations are still relatively high. For Arrival Types 3 and 5 the HCM estimates the delays accurately. These findings suggest that the HCM PFs need to be revised. A new set of PFs was developed using the arrival-based delay models. A relationship between the effective green ratio, g/C, and the new PFs was established for each arrival type. With the proposed PF values, the HCM approach would be more accurate than it is with the current PF values. For Arrival Type 1, the new PF values are higher than the current HCM values for g/C ⩽ 0.50 and lower for g/C > 0.50. For Arrival Types 2 and 4, the new PF values are lower than those of HCM, as expected, because the HCM overestimates the delays for both Arrival Types 2 and 4. For Arrival Type 6 the new PF values are lower for g/C ⩽ 0.40; otherwise they are higher. A new progression adjustment table similar to Table 9-13 of the HCM is created. It is recommended that the new PF values be adopted by the HCM since they enhance the accuracy of delay estimation.

Accounting for Nonrandom Arrivals in Estimate of Delay at Signalized Intersections

The primary objective of this research was to determine the effect of nonrandom or platoon arrivals on the estimate of delay at signalized intersections. The delay model used in the 1994 Highway Capacity Manual (HCM) accounts for nonrandom arrivals through the variable m, which can be shown to be equal to 8kI, where k describes the arrival and service distributions at the intersection and I describes the variation in arrivals due to the upstream intersection. The 1994 HCM delay model m-values are a function of the arrival type, where the arrival type describes the quality of progression at the intersection. Although an improvement to the fixed k I-value used in the 1985 delay model, the 1994 m values are based on empirical studies from limited field data and do not account for the decrease in random arrivals as the volume approaches capacity at the downstream intersection. This research provides an estimate of the variable kI for arterial conditions. An analytical equation was developed as a function of the degree of saturation, and a separate equation was developed for each signal controller type. The results from this research show that the proposed kI's provide delay estimates closer to the measured delay compared with the delay estimates using the kI-values in the 1994 HCM delay model.

Accounting for Nonrandom Arrivals in Estimate of Delay at Signalized Intersections

The primary objective of this research was to determine the effect of nonrandom or platoon arrivals on the estimate of delay at signalized intersections. The delay model used in the 1994 Highway Capacity Manual (HCM) accounts for nonrandom arrivals through the variable m, which can be shown to be equal to 8kI, where k describes the arrival and service distributions at the intersection and I describes the variation in arrivals due to the upstream intersection. The 1994 HCM delay model m-values are a function of the arrival type, where the arrival type describes the quality of progression at the intersection. Although an improvement to the fixed kI-value used in the 1985 delay model, the 1994 m values are based on empirical studies from limited field data and do not account for the decrease in random arrivals as the volume approaches capacity at the downstream intersection. This research provides an estimate of the variable kI for arterial conditions. An analytical equation was developed as a function of th...