Interruption Conditions Research Articles

Impact of stochastic vehicle generation on traffic microsimulation model output

One of the most important characteristics of microsimulation is the ability to model the temporal and spatial nature of traffic demand. Every traffic microsimulation has a vehicle generation model that determines how and when the driver–vehicle units are introduced in the simulation. While microsimulation use has become increasingly popular, it is unclear how the vehicle generation options affect the final result. The purpose of this paper is to examine the stochastic component of the vehicle generation model and how it may affect the simulation output. Three scenarios, including the passenger car equivalent (PCE) model of the Highway Capacity Manual (HCM-7), were used for assessing stochastic volumes and their impacts on performance measures. Results indicate a statistically significant impact of the variability of stochastic volumes on the estimation of performance measures at the breakdown flow phase and synchronized flow phase for interrupted and uninterrupted flow conditions, respectively. This finding highlights the importance of reporting vehicle generation as a calibration parameter, enabling others to replicate the experiments. When utilizing microsimulations for the assessment of roadway/system performance, it is crucial for users to have a thorough understanding of demand generation.

The effects of different interruption conditions on mental workload: an experimental study based on multimodal measurements

Interruptions in the working environment cause extra mental workload for the operators, and this phenomenon has garnered significant research attention. This study designed four interruption conditions based on the perceptual and cognitive perspectives of human information processing, using a 2(perceptual primary task and cognitive primary task)*2(perceptual interruption task and cognitive interruption task) factorial design. Multimodal measurement methods were used to evaluate mental workload in different interruption conditions. The results show that when the primary task and the interruption task are different load types, they generate a higher mental workload than the same load type. It can be attributed to the fact that perceptual tasks and cognitive tasks increase mental workload during switching. In addition, based on the multimodal index data, the prediction model of interruption recovery delay time and the classification model of interruption conditions are established, which provides a basis for rational scheduling of work and preventing mental overload.

A distributed coordinated control strategy for isolated AC microgrids based on consensus algorithm considering communication delay

AbstractIn the multi‐paralleled converter microgrid system, the traditional hierarchical control strategy can eliminate the bus voltage amplitude and frequency deviation from the rated value. However, isolated AC microgrids may face extreme scenarios such as communication delays and interruptions in data transmission due to the use of low‐bandwidth communication (LBC) lines. Additionally, the inconsistent line impedance of each distributed generation (DG) unit may result in the inaccurate division of reactive power in multi‐paralleled converter systems, thus affecting system stability. To address these issues, this paper presents a distributed coordinated control strategy for isolated AC microgrids based on the consensus algorithm. The proposed strategy first replaces LBC lines with a filter to alleviate the effects of communication delays. A small‐signal model is established in its state space, and stability of the microgrid system under the proposed control strategy is verified through eigenvalue analysis. Furthermore, based on the above theoretical analysis, a consensus algorithm is introduced, and a distributed control strategy for isolated AC microgrids based on the consensus algorithm is proposed to solve the issue of inaccurate equalization of the system's reactive power. Finally, factors that influence the dynamic convergence performance of the consensus algorithm are analyzed through simulation in PLECS software. Also, the maximum tolerable communication delays of the microgrid system under different communication topologies are also compared, and the system's robustness is evaluated under the condition of sudden communication interruption in a DG unit and sudden weather variation. These analyses confirmed the robustness of the proposed strategy against communication delays, output power fluctuation, and communication interruptions.

Creep cavities and carbide evolution in interrupted creep conditions along P91 steel of dissimilar weld joint

The creep behaviour of dissimilar weld joint of 316LN SS-P91 steel when subjected to lower applied stresses (below 100 MPa) generally fails in a Type-IV pattern. The dissimilar weld joint was welded through shielded metal arc welding (SMAW) process with INCONEL as electrode, a nickel-based superalloy. An interrupted creep test was carried out at creep condition of 80 MPa −600 °C temperature. Interruption was done at two stages of creep, i.e. (a) mid of secondary and (b) start of tertiary. Microstructural evolution with respect to the hardness variation along various regions of P91 steel at interrupted and the failed specimen was done. A coarsening of hierarchical boundaries and M23C6 carbides was observed along HAZ region that has resulted with respect to time and temperature.

Analyzing river disruption factors and ecological flow in China's Liu River Basin amid environmental changes.

Water resources variability and availability in a basin affect river flows and sustain river ecosystems. Climate change and human activities disrupt runoff sequences, causing water environmental issues like river channel interruptions. Therefore, determining ecological flow in changing environments is challenging in hydrological research. Based on an analysis of long-term changes in hydrological and meteorological variables and interruption conditions in the semi-arid Liu River Basin (LRB), this study summarizes the controlling factors of river interruption at different temporal and spatial scales and proposes a framework to determine ecological flow under changing environments. Hydrological model and the monthly optimal probability distribution were used to determine the optimal ecological runoff of LRB. The results showed that from 1956 to 2017, precipitation and potential evapotranspiration in the basin showed no significant decreasing trend, but the streamflow significantly decreased, and the downstream interruption worsened, with an average annual interruption duration of 194days at Xinmin Station from 1988 to 2017. The controlling factors of river interruption are as follows: (1) soil and water conservation measures in the upstream significantly reduce the runoff capacity; (2) the operation mode of the controlling reservoir in the middle reaches changes from "all-year discharge" to "winter storage and spring release" to "combined storage and supply," severing the hydraulic connection between upstream and downstream; and (3) siltation in the downstream river channel coupled with over-extraction of groundwater increases the seepage capacity of the river. The monthly ecological flow of Naodehai Reservoir was determined by considering the monthly seepage losses after reconstructing the natural runoff using the SWAT model and determining the optimal probability distribution function for monthly runoff. The findings are important for downstream LRB ecological restoration and for determining the ecological flow of other river basins in changing environments.

Comparative Analysis of Deterministic Fundamental Diagrams Representative of Continuous and Interrupted Traffic Flow on Selected Regional Road in Croatia

Since the inception of the traffic flow theory, numerous traffic flow models have been formulated by scholars in an effort to more accurately delineate the relationships between various traffic flow parameters. However, only a limited number of studies have explored the distinctions between fundamental traffic diagrams, which characterize continuous and interrupted traffic flow conditions. Addressing this research lacuna, we compared twelve “speed–density” and “flow–density” models fitted to empirical data collected under continuous and interrupted traffic flow conditions on a selected regional road in Croatia. The empirical data used to develop these models were extracted from video footage captured by an unmanned aerial vehicle on two representative road segments during characteristic peak and off-peak hours on workdays. Our analysis reveals that, depending on the selected traffic flow model and prevailing traffic flow conditions, the practical capacity of the observed regional road is estimated to be in the range from 799 to 2333 veh/h/lane. It was also discovered that the considered models reach practical capacity at a significantly different density under continuous and interrupted traffic stream conditions, i.e., between 37 and 129 veh/km/lane. The conducted t-tests underscore the need to employ distinct “speed–density” and “flow–density” regression functions for modeling continuous and interrupted traffic stream conditions.

Characterization and modelling of microstructure evolution during partitioning in Q&P steels

Development of a simulation methodology and model which combines the analytical estimation of the microstructure at different points of the Q&P route with the numerical modelling of the main physical phenomena during partitioning was done. Detailed characterization of microstructure was performed at different stages of the Q&P process: at the quenching temperature (QT), at different interrupted conditions of partitioning and after final cooling down to room temperature. In addition, some investigations during the heating step from quenching to partitioning temperature was done by measuring the RA fraction. Then, the evolution of carbon free bainite and retained austenite phase fraction during the partitioning and different processing conditions was analyzed. The austenite grain size distribution produced by the first quenching was experimentally characterized and implemented in the model. Modelling approach to describe the main phenomena taking place during the partitioning step, i.e. carbon diffusion and bainite formation, was proposed. The built one-dimensional model predicts the microstructure evolution during partitioning step in the Q&P processing: starting from quenching temperature and going to the final cooling to room temperature. Finally, model performance was evaluated using two experimental datasets: one for testing and another for the validation.

Study on sewage characteristics in rural China and pollutants removal performance of biologically enhanced internal circulation treatment system

With rapid economic development and urbanization in China, rural wastewater treatment has become an important issue. This study investigated 63 rural sewage treatment stations in northern, central and southern Shaanxi, China for a 1-year period, 2021 to 2022. The main purpose of the research was to investigate the quality and discharge characteristics of rural sewage, along with current problems in rural wastewater treatment, in order to provide evidence for the optimal construction and operation of rural sewage treatment stations. We found that the biodegradability of rural wastewater is adequate, and BOD5/COD ratio in sewage was 0.4, which is suitable for biological treatment. It has obvious intermittent flow cut-off characteristics, and the range of cut-off duration of sewage was 6–16 h/d, which leads to poor pollutant removal efficiency (COD: 50.0 ± 29.2%, NH4+-N: 46.0 ± 26.1%, TN: 38.5 ± 24.9% and TP: 38.3 ± 23.8%) in sewage treatment stations. In response to the above characteristics, the rural sewage biologically enhanced internal circulation treatment (BEICT) system was constructed. After 97 days of operation, the system has a stable removal effect on TN and TP with an average removal rate of 77.42% and 89.69%, respectively, under the condition of influent interruption for 12 h per day. The activated sludge of system maintained good activity and stable sedimentation performance during the whole experiment, with MLVSS/MLSS and SVI of 0.72 and 128 mL/g, respectively. This study can provide the basis and technical support for the accurate design of rural sewage treatment facilities, and has important significance for guiding the treatment of rural domestic sewage in China.

Internal State of Fuse Arc Differentiating Interruption Success and Failure in Fuse‐SemiconductorDCCircuit Breaker

For the realization of sustainable society installing renewable energy sources, we have proposed a compact, low‐cost, versatile DC circuit breaker that combines a fuse and a power semiconductor. However, even under the same interruption conditions, there are cases where the interruption success and failure are observed probabilistically; the reason for this is still unknown. In the interruption failure, thermal reignition of an arc discharge occurs inside the fuse under transient recovery voltage. In this study, the spatiotemporal dynamics of the fuse arc was diagnosed for both interruption success and failure by a voltage–current waveform recording, high‐speed arc‐emission videography and borescope‐integrated optical emission spectroscopy, in order to identify the difference between the interruption success and failure. The waveform recording and videography demonstrated that at the arc initiation inside the fuse, the radial arc length for the interruption failure was longer than the interruption success. In the current interruption phase, the radial arc length was still longer, axial arc length was shorter, and arc column resistance was lower for the interruption failure. Further, the optical emission spectroscopy showed that localized regions with higher temperature and electrical conductivity existed for the failure in the current interruption phase. From these results, the dominant factors differentiating interruption success and failure were identified as the arc shape and electrical conductivity of the arc. To improve the interruption performance of the fuse and our DC circuit breaker, it is effective to increase the axial arc length, suppress the radial arc length, and reduce the electrical conductivity of the arc. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

ЗАКОНОМІРНОСТІ ЗМІНЕННЯ ЕНЕРГОЕФЕКТИВНОСТІ РОЗРЯДУ СУПЕРКОНДЕНСАТОРА НА ЛІНІЙНЕ АКТИВНЕ НАВАНТАЖЕННЯ ПРИ ЗМІНІ ТРИВАЛОСТІ РОЗРЯДУ

In the paper, the regularities of changes in electricity losses and the coefficient of its transfer to a linear active load during the discharge of a supercapacitor on the load under different conditions of interruption of discharge currents are determined. The influence of the conditions of interruption of discharge currents of the supercapacitor on the energy characteristics of the discharge circuit is determined, taking into account the fact that the capacity of the supercapacitor is a function of the voltage at its terminals. It was taken into account that this voltage can change its polarity. A mathematical model was developed that takes into account that the discharge process can be both aperiodic and oscillatory. The model was implemented in the Mat-lab/Simulink software package. A comparison of the energy characteristics during the discharge of a supercapacitor and a conventional linear capacitor on the same linear load at the same initial voltage on these capacitors was carried out. It has been established that the energy delivered to the load during the discharge of a supercapacitor is 1.8 times greater than dur-ing the discharge of a conventional linear capacitor charged to the same voltage, but the efficiency of energy transfer for these processes is almost the same. However, when the discharges of a supercapacitor and a conventional linear capacitor are forcibly interrupted, the efficiency of energy transfer to the load increases, and the efficiency during the discharge of the supercapacitor is always higher. Bibl. 14, fig. 3, tables 2. Key words: supercapacitor, capacitor, discharge, linear load, electricity losses, energy transfer efficiency.

Biological stress responses to multitasking and work interruptions: A randomized controlled trial

In the course of digitalization, new stressors are emerging. In modern working and living environments, two ubiquitous, technology-mediated stressors are multitasking demands and work interruptions. However, biological stress response patterns to multitasking and work interruptions have been sparsely investigated so far. We thus aimed to comprehensively assess biological stress response patterns to both stressors and, additionally, test whether responses differ between digital and partially non-digital settings. A controlled experimental set-up was established and humans’ biological markers of the Sympathetic Nervous System (SNS), the hypothalamic-pituitary adrenal (HPA) axis, and the immune system were assessed. N = 186 healthy participants (mean age: 23.2 ± 4.3 years, 74.7% female, body mass-index: 22.3 ± 3.1 kg/m2) took part in this pre-registered study. Each participant was randomly assigned to one of 6 experimental conditions (1 digital single-task, 3 dual-tasks [2 parallel tasks and 1 interruption], 1 multitasking, and 1 passive, control condition). Each one of the dual-tasking as well as the multitasking conditions included a non-digital sub-task, i.e., performing a task in presence of an examiner. All other conditions involved digital tasks only. Salivary alpha-amylase (sAA) levels as a marker for SNS reactivity significantly changed in work interruptions, parallel dual-tasking, and multitasking conditions. No changes were found for control conditions. Furthermore, no significant changes over time and no differences between the conditions were identified for three biological markers: cortisol as marker for HPA axis activity as well as for two immune system markers (secretory Immunoglobulin-A, C-reactive protein). A time course similar to sAA was found for perceived stress: with increases during task execution and decreases afterwards in multitasking and parallel dual-tasking. Yet, it did not change for the work interruption, passive control, and single-tasking condition. Overall, our findings show that dual- and multitasking are perceived as stressful and are associated with an activation of the SNS, but not with responses of HPA axis or immune system. This was consistent for digital as well as partially digital task demands. Our findings will also inform future research into the differential stress effects of digital and non-digital tasks to advance our understanding of biological stress response-patterns to multitasking and work interruptions. Therefore, our findings are highly relevant for understanding the long-term biological health effects of stress in modern (digitalized) environments.

EEG-based Objective Quality Assessment of Interrupted Speech.

As an important dimension of speech degradation, interruption destroys the acoustic waveform information of a speech signal and seriously affects the quality rating in speech perception. Existing studies assessing the quality of interrupted speech mainly focus on subjective methods. This work used event-related potentials (ERPs) to objectively investigate the effects of two interruption factors (i.e., interruption duty cycle and interruption rate) on the perceived quality of the periodically interrupted speech. An oddball-paradigm based ERP experiment was designed, and the periodically interrupted stimuli were presented to participants in the ERP experiment. Meanwhile, participants were instructed to provide their subjective quality ratings of interrupted speech under the same interruption conditions. The experimental results showed that the degree of both interruption duty cycle and interruption rate affected the peak latency of mismatch negativity (MMN) of the collected ERP response, with a smaller MMN peak latency under conditions with a smaller interruption duty cycle or a larger interruption rate. These findings are largely consistent with the subjective quality rating results, suggesting that the peak latency of MMN response can be potentially used as an objective quality indicator of the periodically interrupted speech.

Effects of different types of interference on nurses' working memory: An ERP study.

To explore the effects of different types of interference on nurses' working memory, and the role of attention control. A repeated measures design. A single-factor, four-level within-subjects design was adopted. Thirty-one nurses completed a delay-recognition task with four blocks in September 2020: Interrupting Stimulus (stimuli requiring attention), Distracting Stimulus (stimuli to-be-ignored), No Interference and Passively View. Behavioural responses of the participants and EEG data were recorded. MATLAB 21b and EEGLAB 21b were used for electroencephalogram data preprocessing and data extraction. Firstly, when nursing information system was used as task material, the accuracy rate and false alarm rate of primary tasks under interruption condition was statistically significantly different with that of distraction and no interference condition. There is a statistically significant difference in electroencephalogram measurement between correct and wrong response under interruption. Secondly, the role of attention control was different under interruption and distraction. There was a statistically significant positive correlation between the average amplitude distraction attention control index and task accuracy, and statistically significant negative correlation between the latency interruption attention control index and the accuracy of working memory task. There were different effects of interruptions and distractions on nurses' working memory and the role of attention control were also different. Measures can be designed according to these results to reduce the negative impact of interference on nurses, so as to improve work efficiency and reduce patient risk. This study has implications for clinical nursing during human-computer interaction. Resumption of the speed of the target information after an interruption affected task performance. Therefore, interventions should be designed to reduce the time needed for nurses to extract task information after an interruption, such as providing key clues in the information system interface. Registered nurses participated in the study as subjects.

Investigation of the Effect of Thermal Tension in Hot Seasons and Interruption of Irrigation at the End of the Growth Season by Silicon Nutrient Solution Sulfonated With S8 Elemental Sulfur on Fresh and Dry Fodder Yield and Protein Content of Alfalfa (Medicago sativa L.)

This research is an introduction to the combined nutrient of mineral salts by Silicon sulfonated with S8 through aerial organs of the Alfalfa plant. This type of combined nutrition by S8 is called “Matrix Nutrition”. This experiment was launched in October 2022 to study the effect of S8 on increasing the yield of fresh and dry fodder and the percentage of Alfalfa protein content using combined nutrition or Matrix Nutrition on the aerial organ of Alfalfa plant in the condition of interruption of irrigation at the end of the growing season in Moghan region, Ardabil province in Iran. The experiment was carried out in 2 plots, each one being one-hectare land. (In the first plot, S8 was applied for 5 litres per 1000 litres of water in the growth stages as foliar spraying after each crop harvest. No S8 was applied in the second plot.) The 5th and 6th harvests coincided with a dry season in this region and no irrigation was applied in this experiment for the 5th and 6th harvests. Both plots were only irrigated similarly for 1st to 4th harvest. The results obtained from a total of 5 harvests of the Hamedani Variant Alfalfa plant in the Control Plot and 6 harvests of the Hamedani Variant Alfalfa plant in the Experiment Plot indicated the highest yield in the 1st plot treated with S8 in terms of fresh and dry fodder, percentage of dry materials of fodder and protein content with a significant difference of 1% and 5% compared to Control Plot. The difference between the two plots was: fresh fodder 11,610 Kgs/Hectare, i.e., 91.27% higher yield, dry fodder 4,099 Kgs/Hectare, i.e., 140.95% higher yield, increase in dry material percentage for 5.99% and higher protein content of fodder for 1.59% which indicated a significant positive effect of application of S8 nutrient solution as foliar spraying on the increase of yield in fresh and dry fodder in the growing season and specifically at the time of thermal tension (specifically on 2nd and 4th harvest in control plot on June and August) and interruption of irrigation at the end of growth season (5th and 6th harvest of experiment plot).

Impacts of Victim Resistance and Type of Assault on Legal Decision-Making in Child Sexual Assault

ABSTRACT Prior studies have examined the effects of victim resistance and type of assault (attempted or completed) on perceptions of adult rape cases. However, research has not yet tested whether these findings extend to verdicts rendered in child rape cases, nor has research focused on how perceptions of victim and defendant characteristics in child rape cases may contribute to legal decision-making. In the present study, a 2 (attempted or completed sexual assault) x 3 (victim resistance: verbal-only, verbal with outside interruption, or physical) x 2 (participant sex) between-participant design was used to assess legal decision-making involving a hypothetical criminal case of child rape, with a six-year-old female victim and a 30-year-old male perpetrator. Three-hundred and thirty-five participants read a criminal trial summary and answered questions about the trial, the victim, and the defendant. Results revealed that: (a) when a victim physically resisted, compared to verbally resisted, more guilty judgments were rendered, (b) when the victim physically resisted, higher ratings for aggregated factors for Victim Credibility and Negative Perceptions of the Defendant were given, leading to more guilty verdicts, and (c) female participants were more likely than male participants to render a guilty verdict. No differences in verdict rendered between the verbal with interruption (e.g., knocking on door) and verbal-only conditions were found, nor did type of assault lead to differences in verdict rendered. Implications for child sexual assault cases and the courtroom, as well as implications for practitioners, are provided.

RESOURCE LEVELLING IN REPETITIVE CONSTRUCTION PROJECTS WITH INTERRUPTIONS: AN INTEGRATED APPROACH

Despite the significance of resource levelling, project managers lack various ways to smooth resource usage fluctuation of a repetitive construction project besides changing resource usage. Tolerating interruptions is an effective way to provide flexibility for a schedule but is ignored when solving resource levelling problems. Therefore, this paper investigates the impacts of interruptions on resource usage fluctuation and develops an integrated approach that simultaneously integrates two scheduling adjusting processes: changing resource usage and tolerating interruptions. In this paper, two interruption conditions are proposed to identify which activities are suitable to be interrupted for smoothing resource usage fluctuation. The traditional resource levelling model is modified to a new scheduling model by incorporating interruptions. A two-stage GA-based scheduling algorithm is developed by integrating changing resource usage and tolerating interruptions. A commonly used pipeline project is adopted to illustrate the steps of the proposed approach and demonstrate its effectiveness and superiority through comparison with previous studies. A large-scale project further verifies the usability of the proposed approach. The results confirmed the feasibility to smooth resource usage fluctuation by interruptions, and the integrated approach can achieve a more competitive resource levelling result.

Does friction contribute to formability improvement using servo press?

Servo press forming machines are advanced forming systems that are capable of imparting interrupted punch motion, resulting in enhanced room temperature formability. The exact mechanism of the formability improvement is not yet established. The contribution of interrupted motion in the ductility improvement has been studied through stress relaxation phenomena in uniaxial tensile (UT) tests. However, the reason for improved formability observed when employing servo press is complicated due to the additional contribution from frictional effects. In the present work, an attempt is made to decouple the friction effect on formability improvement numerically. The improved formability is studied using a hole expansion test (HET). The limit of forming during hole expansion is modeled using the Hosford-Coulomb (HC) damage criteria, which is implemented as a user subroutine in a commercial explicit finite element (FE) software. Only the contribution of stress relaxation is accounted for in the evolution of the damage variable during interrupted loading. Therefore, the difference between simulation and experimental hole expansion ratio (HER) can be used to decouple the friction effect from the overall formability improvement during hole expansion. The improvement in HER due to stress relaxation and friction effect is different. The study showed that the model effectively captures the hole expansion deformation process in both monotonic and interrupted loading conditions. Compared to stress relaxation, friction effect played a major role during interrupted HET.

Research on the construction scheme of the emergency communication link in electric power system without public network signals

Recently, natural disasters have occurred frequently which usually cause great damage to communication links. Emergency communication technology is the key technology to connecting the emergency site and the command center under the condition of communication system collapse, and it plays an extremely important role in the process of emergency rescue. Based on the disaster scene of the electric power system, this paper fully considers the extreme conditions of power outages, network disconnection, and traffic interruption at the emergency site, and proposes an emergency communication link construction scheme. After the pilot test, the scheme proposed in this paper can quickly restore the network signal coverage of the emergency site, and establish the communication link between the command center and the emergency site which can provide a reliable communication guarantee for power emergency rescue operations.

Adaptive prescribed time control for quadrotor formation with stochastic links failure

AbstractThe formation control for multiple quadrotors subject to maintaining the formation configuration and collision avoidance in the situation of stochastic links failure is investigated in this paper. First, the distributed formation controller is designed, the position controller is developed to manage the desired formation of position, and the attitude controller is developed to control the translation and rotation movements of the quadrotor. Then, in order to avoid the collisions between multiple quadrotors and the obstacles, a potential energy function method is introduced into the quadrotor formation control combined with the nest adaptive control. Inspired by the design of event trigger controller, a communication compensation controller is designed to ensure the stability of quadrotor formation under the condition of random communication interruption and recovery. Moreover, a prescribed time function is designed, which means the convergence time of the formation system can be set in advance. The prescribed time stability of the formation control system is proved by Lyapunov theory. Finally, the simulation results verify the effectiveness and superiority of this method.

Characterization of heavy vehicle headways in oversaturated interrupted conditions: Towards development of passenger car equivalency factors

Passenger car equivalency (PCE) of heavy trucks is often studied using filed observation and microscopic simulation models, especially for signalized intersections. While the Highway Capacity Manual recommends a single value regardless of the percentage of those heavy vehicles, literatures have shown that this equivalency is affected by different factors, including the trucks percentage. This research aims to examine the PCE under different level of traffic and heavy trucks demands. First, field measurements were collected and used to examine the characteristics of heavy vehicle and passenger car headways in oversaturated interrupted flow conditions. Field observations were then used to calibrate a microscopic simulation model. The model was then used to evaluate impact on headways of different levels of congestion and heavy vehicle percentages. Field results show that truck headways are about 2.3 those of passenger cars. The results also show that trucks are 1.5 more likely to be first in a queue when compared to passenger cars and 1.7 times more likely to be in first four vehicles in a standing queue. Passenger cars immediately behind trucks had longer than average headway. The simulation results suggest that PCE increases nonlinearly with increase in congestion level and with percentage of trucks; PCE's increase becomes less marked once sever congestion (stop-and-go with increasing queue lengths) conditions set in.