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This paper presents a comfort-enhanced vibration control design approach for vehicle active suspensions with control delay. By introducing some novel relaxed inequalities, a less conservative bounded real lemma is derived such that the suspension system is asymptotically stable and has an enhanced vibration attenuation performance in the presence of road disturbance and control delay. In the control design, an augmented Lyapunov–Krasovskii functional is proposed to enlarge the degree of freedom of design. A suitable controller can be obtained via a sufficient condition with linear matrix inequality constraints. Compared with the previous methods based on frequently used inequalities and the traditional Lyapunov–Krasovskii functional, the proposed controller can provide better comfort performance for different control delays. Finally, the advantages of the proposed method are demonstrated using numerical examples.

The level of service of an intersection is determined principally by control delay. Accordingly, control delay must be reproduced correctly when microscopic traffic simulation is used to evaluate intersections. This study demonstrated how Vissim could be calibrated for that purpose. Vissim models of four signalized intersections for which data had been collected were built. From these data, information that was extracted on headways, time to pass the intersection, and arrival distribution was used for calibration. Calibration of the headways resulted in car-following parameters for these intersections that differed substantially from the Vissim default values. An adjustment in the vehicle arrival distribution to the observed distribution was also necessary to reproduce the measured delay in the simulation.

In the United States, roundabouts have recently been constructed to replace signalized intersections at freeway ramp terminals as both a safety and an operational treatment. In practice, this treatment is in need of guidelines specifying conditions when the roundabout or signalized intersection is more appropriate to assist practitioners in deciding which alternative to choose. In particular, research providing a comprehensive operational comparison between roundabouts and signalized interchanges is lacking. The current research—though a strictly calibrated microscopic simulation platform—analyzes and models the control delay at double-lane roundabouts and signalized interchanges. Both roundabouts and signalized interchanges were modeled in a Vissim simulation platform. Capacity at each roundabout entrance was calibrated and validated separately for passenger cars and heavy vehicles, since both vehicle types have different critical and follow-up headways. The design of the simulation experiments covered 2,880 different scenarios for roundabouts and signalized interchanges with varying ramp and arterial volumes, ramp spacing, and heavy-vehicle percentages. From the simulation results, control delay and level of service of the off-ramp and arterial approaches of roundabouts and signalized diamond interchanges were modeled and compared. Ultimately, guidelines for the selection between double-lane roundabouts and signalized interchanges were developed and presented in the form of look-up tables. These tables provide an easy-to-use tool for practitioners to determine the appropriate double-lane interchange to install under specific combinations of traffic demand, heavy-vehicle percentage, and ramp spacing conditions.

Two types of delay variability have been commonly referred to at signalized intersections: arrival-time-dependent individual vehicle delay variability and average control delay variability. The former focuses on the delay experienced by individual vehicles, whereas the latter deals with the average consequence of signal control for the entire traffic flow during a given evaluation period. With a number of methods available for estimation, little research has been conducted to enable a comprehensive comparison of these two variability measures. This issue is addressed by a comparison of these two types of delay variability at isolated, fixed-time controlled intersections based on two analytical models accounting for the stochastic nature of traffic arrivals and overflow queues. The results show that in undersaturated conditions, individual vehicle delay tends to have a wider distribution and a larger variance compared with average control delay. In oversaturated conditions, the shapes of both types of delay distributions shift to the higher values with larger variances. Different arrival processes are found to have a significant influence on the pairwise delay distributions. In addition, the width of the delay distribution based on percentiles is used to quantify the delay uncertainty under different degrees of saturation. Compared with average control delay, individual vehicle delay is found to have a larger uncertainty in undersaturated conditions, whereas it becomes relatively certain in oversaturated conditions. All the analyses have special practical implications for enriched knowledge of stochastic arrival and departure processes at signals.

A rapid iterative learning control algorithm with variable forgetting factor is applied for a class of nonlinear system with initial error and time-delay. This algorithm eliminats the limitation that the initial state should be reset to the expected one or fixed value at the start of iteration in the learning process of conventional algorithms. The error and the differences between two adjacent error is adopted to correct the controller avoiding the unstable influence of the derivative for PD type algorithm and the available information is fully used to increase convergence rate. Furthermore variable forgetting factor introduced guaranteed a fast convergence of trajectory tracking error Then, with applying the rapid algorithm to the trajectory tracking control of manipulator, the learning speed and tracking performance are both greatly improved. Meanwhile, the control strategy is proposed for the limitation of each joint rotation. The convergence of the method is also proved theoretically. Finally, simulation results illustrates the effectiveness and the real-time ability of the proposed way.

Teleoperation of unmanned aerial vehicles is hampered by communication delay, which causes feedback from command inputs to take considerable time to be displayed to the operator. For an international internet connection, round trip latencies can reach 500 ms. The satellite connections used for military unmanned aerial vehicles can have latencies in the order of seconds. This delay presents a substantial control problem, which has been solved in the past by control abstraction (instead of “roll left” the aircraft might be instructed “go to these coordinates”). Manual control remains difficult. This study borrows the client-side prediction concept from multiplayer video games to attempt to address the control delay to allow manual control. An estimate of the change in the vehicle state due to the commands that are yet to affect the feedback is computed and then the feedback that the pilot receives is modified to reflect this predicted change. Because of this change, the pilot can see immediately the effect of the control inputs. This study has explored the concept and built a prototype system functional in real time for flight testing with qualitative results presented.

The motor vehicle emission simulator (MOVES) modeling software of the U.S. Environmental Protection Agency enables researchers and practitioners to model vehicle emissions at the project level. With this tool, agencies can identify and evaluate the effectiveness of local traffic control strategies to reduce emissions at project hot spots, such as congested intersections. This study analyzes vehicle emissions at congested and uncongested signalized intersections under three traffic intersection scenarios, ranging from Level of Service (LOS) B to LOS E. Emissions are much less sensitive to congestion than control delay. A shift in operation from LOS E to LOS B reduced per vehicle nitrogen oxide emissions by 15% and particulate matter emissions by 17%, while control delay decreased by 40%. The largest sources of emissions were cruising and acceleration; they accounted for more than 80% of total emissions under all scenarios. Idling accounted for less than 18% of all intersection emissions. This analysis calculates emissions with a time-in-mode methodology that combines emission factors for each activity mode (i.e., acceleration, deceleration, cruise, idle) with a calculation of the total vehicle time spent in that mode. This approach demonstrates the contribution of each activity mode to intersection emissions and suggests opportunities for control strategies with the potential to affect intersection emissions. The streamlined methodology may be a helpful tool for agencies that are interested in analyzing project-level emissions and control strategies, but lack staff resources or expertise for microsimulation-based scenario analysis.

Diverging diamond interchange (DDI) is a form of diamond interchange attracting growing interest from traffic engineers and researchers. Conventional control delay calculation models are not effective when applied to DDI because of the possible internal queue spillback. This paper describes a method to calculate control delay at DDI using a new analytical model. The model was first developed for control delay calculations of external movements at conventional diamond interchanges. Through the addition of a function to calculate delay of internal movements, the model was successfully used at a DDI to calculate control delay of both internal movements and external movements. Simulation studies are also conducted to validate the new model. This study can be used either as a stand-alone delay calculation model or as a supplement to existing simulation methods. The model also shows promise for use in other signalized interchange configurations with two or more adjacent intersections.

The Highway Capacity Manual (HCM) is one of the most widely used transportation documents in the world. The signalized intersections methodology, one of the most frequently used portions of the manual, is used to estimate capacity and average control delay for individual lane groups and for intersections as a whole. The method does not estimate control delay for vehicles permitted to turn right on red, nor does it include these vehicles in the computation of capacity. It is recognized that vehicles making right turns on red (RTORs) increase intersection capacity. Thus, capacity, delay, and level of service may not be predicted accurately when RTORs occur. For the specific case in which a shared through and right-turn lane exists and RTORs are permitted, models were developed to estimate the number of RTORs that can be expected and the additional capacity that is realized. The models are deterministic and are consistent with the HCM methodology, are easily understood by analysts, produce reasonable results, and account for the probabilistic nature of RTORs occurring from shared lane approaches. The capacity model also demonstrates that, where RTORs are permitted and do occur, the HCM method results in an underestimation of capacity and an overestimation of delay for approaches containing shared lanes.

This research examined the operations of a four-legged, two-lane modern roundabout with different combinations of approach volumes. Because of the insufficient number of roundabouts to collect field data, experiments were performed with the VISSIM microscopic traffic simulation model. The model's parameters were calibrated with real data collected at a four-legged, two-lane modern roundabout. Different combinations of approach volumes, which ranged from 400 to 1,600 vehicles per hour, were simulated to create relatively high or low traffic demand in one or two approaches. The performance of each roundabout approach was measured by average control delay and level of service. The results of the experiments highlight the potential operational issues of four-legged, two-lane modern roundabouts. The results are presented in three charts that may serve as a quick reference guide for engineers to determine whether a roundabout is a feasible type of intersection control for a given set of design volumes before in-depth engineering analysis is performed.

The Highway Capacity Manual (HCM 2000) displayed the figure Exhibit 10-15 for the purpose of forecasting the likely intersection control types for future facilities. Because this figure is from a source external to HCM, to verify it, this paper employs HCM methodologies for the estimation and comparison of control delay, the choice measure of effectiveness at intersections controlled by signal, all-way stop signs, and two-way stop signs. After detailed analyses of more than 5,000 cases using Highway Capacity Software, results of control delay with various control types under a wide range of demand conditions were charted for comparison with Exhibit 10-15. It is found that Exhibit 10-15 is inconsistent with the results from HCM methodologies and, perhaps, should be replaced with the figures developed in this paper. On the basis of the criterion of minimizing delay alone, it is found that if demand is unbalanced between major and minor streets and if the traffic is low on minor streets, two-way-stop control should be used; if demand is somewhat balanced and minor streets see low to medium traffic, all-way-stop control is preferred; otherwise, signal control should be favored. The paper also demonstrates that the percentage of left-turning traffic has a significant effect on decisions involving intersection control types.

Control delay for left-turning vehicles at unsignalized intersections was observed in the field and compared with average control delay calculated from the methodologies presented in the 1997 update of the Highway Capacity Manual (HCM). Unsignalized intersections with two-way left-turn lanes on the major street were observed in the peak and offpeak hours, and control delays were recorded for the one-stage and twostage left-turn processes. Next, the methodologies presented in the HCM were used to calculate the control delay for both processes and compared with the observed data. These comparisons were used as the basis for validation of the HCM methodologies regarding left-turn control delay at unsignalized intersections. From the comparisons, the calculated delay closely corresponds with the observed data, with a total approach volume at the intersection of approximately 2,500 vehicles per hour or less. Once the total approach volume increases above this level, the calculated values rapidly increase and the actual observed control delays gradually increase at a much lower rate. As a result, the observed and calculated delays are different when the intersection handles more than 2,500 approach vehicles in an hour. Statistical analyses were performed on the data to determine if the average observed control delay was related to the calculated control delay. Statistically, the observed control delay and the calculated control delay at the 95 percent confidence level show that the two data sets yield similar results for off-peak conditions. However, during the peak hour, when the total approach volumes are higher, the 95 percent confidence interval yields different results. Hence, the HCM procedures produce, on average, greater control delay estimates than the field observations when the total approach volumes are high.

Roundabouts are a form of at-grade intersection control that is used frequently around the world and is becoming popular in the United States. Roundabouts are being used to replace two-way and all-way stopcontrolled intersections and traffic signals in the United States. Roundabouts have also been used recently in Vail, Colorado, to improve an existing stop-controlled freeway interchange system. In this study, five single-lane roundabouts are studied to assess their safety and operational performance. All five sites were stop-controlled before roundabouts were installed, and overall the sites experienced a reduction in accident frequencies, rates, and also control delay. Aside from a review of safety and delay data before and after installation of the roundabouts, this study includes a comparison of field-measured control delay with that predicted by SIDRA, an analytically based software package that can analyze at-grade sign- and signal-controlled intersections as well as roundabouts. This study will help agencies better understand their ability to predict delay at American roundabouts. Finally, findings are presented regarding the accuracy of the roundabout capacity model contained in the 1997 update to Chapter 10 of the Highway Capacity Manual. Because of the lack of roundabout entries that are operating at capacity in the United States, an approximation of potential capacity based on available gaps in the circulating stream was made. These findings indicate that the manual may be optimistic in its prediction of capacity for single-lane roundabouts in the United States; however, it should be noted that the lack of roundabout entries operating under capacity in the United States only allows for an approximation of field capacity to be made at this time.

Visual compensatory, visual pursuit, auditory compensatory, and auditory pursuit tracking of 20 male college students was observed under the conditions of .000-, .210-, .420-, and .840-sec. transmission type control delay. Tracking efficiency decreased as transmission delays increased; visual tracking was consistently superior to auditory tracking, although the relative degradation across delays was greater for visual than for auditory tracking; and little if any adaptation to the delays was apparent. These results point out the essentially similar effects of delayed sensory feedback on equivalent motion patterns when guided by different feedback modalities.