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Objective To examine the effects of interruptions and retention interval on prospective memory for deferred tasks in simulated air traffic control. Background In many safety-critical environments, operators need to remember to perform a deferred task, which requires prospective memory. Laboratory experiments suggest that extended prospective memory retention intervals, and interruptions in those retention intervals, could impair prospective memory performance. Method Participants managed a simulated air traffic control sector. Participants were sometimes instructed to perform a deferred handoff task, requiring them to deviate from a routine procedure. We manipulated whether an interruption occurred during the prospective memory retention interval or not, the length of the retention interval (37–117 s), and the temporal proximity of the interruption to deferred task encoding and execution. We also measured performance on ongoing tasks. Results Increasing retention intervals (37–117 s) decreased the probability of remembering to perform the deferred task. Costs to ongoing conflict detection accuracy and routine handoff speed were observed when a prospective memory intention had to be maintained. Interruptions did not affect individuals' speed or accuracy on the deferred task. Conclusion Longer retention intervals increase risk of prospective memory error and of ongoing task performance being impaired by cognitive load; however, prospective memory can be robust to effects of interruptions when the task environment provides cuing and offloading. Application To support operators in performing complex and dynamic tasks, prospective memory demands should be reduced, and the retention interval of deferred tasks should be kept as short as possible.

The main goal of this paper is to analyze the relationship existing among prices of alcoholic beverages, alcohol consumption and traffic fatalities for the Spanish Autonomous Communities during the time interval 1998-2002. Among the main results, we highlight a positive correlation between alcohol consumption and traffic mortality rate. Basically, governments implement two kinds of policies to reduce the traffic mortality rate. One is oriented to control the supply of alcohol by increasing alcohol taxes. The other is oriented to preserve traffic security, increasing the number of sanctions for traffic rule infraction. We find evidence that both policies exert a positive influence in the reduction of traffic fatalities. There is no empirical evidence to indicate that being a novice driver increases the tendency to be involved in a mortal traffic accident.

An analysis of the impact of the packetization interval for constant bit rate traffic has been done in the context of the IEEE 802.16 MAC layer. Bandwidth used for overheads which include lower layer headers as well as retransmissions at the MAC layer is considered. An optimal packetization interval selection method for delay sensitive applications such as VoIP is proposed. Enhancements to the Unsolicited Grant Service retransmission strategy are proposed to further improve delay and minimize packet loss while making efficient use of the limited bandwidth resource.

International audience ; The main goal of this paper is to analyze the relationship existing among prices of alcoholic beverages, alcohol consumption and traffic fatalities for the Spanish Autonomous Communities during the time interval 1998-2002. Among the main results, we highlight a positive correlation between alcohol consumption and traffic mortality rate. Basically, governments implement two kinds of policies to reduce the traffic mortality rate. One is oriented to control the supply of alcohol by increasing alcohol taxes. The other is oriented to preserve traffic security, increasing the number of sanctions for traffic rule infraction. We find evidence that both policies exert a positive influence in the reduction of traffic fatalities. There is no empirical evidence to indicate that being a novice driver increases the tendency to be involved in a mortal traffic accident.

The necessity to check requirements for sound insulation of new building façades against outdoor noise and for estimating noise pollution of the residential area comprise the assessment of environmental noise taking in situ measurements that are mainly carried out under the standardized method presented in the EU directives and Lithuanian legislation. For these estimations, annual composite daily equivalent sound pressure levelLden becomes obligatory. When the value of this descriptor is determined from measurements, it is relevant to reasonably reduce a time interval of the performed measurement. The possibilities of determining the noise levelLd,12hof the day (12h) undertaking annualLdenassessment making short-term (15÷60 min.) measurements is dealt in this work. In this way, the sensitivity of the set of statistical descriptors to variations in sound pressure levels was investigated. The paper proposes that the obtained instantaneous A-weighted sound pressure levels with F (fast) time weighting histogram of distribution density may be used for characterizing noise pollution in the sites. When traffic noise emitted from arterial town roads with stationary traffic takes a dominating position, the form of these histograms is close to normal distribution density with corresponding statistical parameters: average, standard deviation, asymmetry coefficient and percentiles. The experimental measurements have established that an asymmetry coefficient and an introduced descriptor– the rank of percentileNeq%are the most sensitive to noise variations. The last one is more preferable due to its exclusive relationships with an equivalent level– the corresponding value of this rank of percentilePNeqthat coincides with the equivalent level of the measured time interval. It has been found that the introduced descriptorNeqis very sensitive for indicating the dissimilarity of environmental noise (the presence of a casual impulse or high energy noise events). In-situ measurements of the vicinity of roads with intensive traffic in Vilnius City, where stationary urban traffic noise is dominating, indicate that the values ofNeqrank obtained during short-term (15÷60 min) intervals in the period from7:00 to 19:00 are stable and vary from 69% to 74%. When non-stability occurs, a significant increase in the values of this descriptor may be applied as criteria for indicating noise events other than traffic noise and may be used for determining the interval limits of short-term stationary measurement. First Published Online: 12 Apr 2011

The necessity to check requirements for sound insulation of new building façades against outdoor noise and for estimating noise pollution of the residential area comprise the assessment of environmental noise taking in situ measurements that are mainly carried out under the standardized method presented in the EU directives and Lithuanian legislation. For these estimations, annual composite daily equivalent sound pressure levelLden becomes obligatory. When the value of this descriptor is determined from measurements, it is relevant to reasonably reduce a time interval of the performed measurement. The possibilities of determining the noise levelLd,12hof the day (12h) undertaking annualLdenassessment making short-term (15÷60 min.) measurements is dealt in this work. In this way, the sensitivity of the set of statistical descriptors to variations in sound pressure levels was investigated. The paper proposes that the obtained instantaneous A-weighted sound pressure levels with F (fast) time weighting histogram of distribution density may be used for characterizing noise pollution in the sites. When traffic noise emitted from arterial town roads with stationary traffic takes a dominating position, the form of these histograms is close to normal distribution density with corresponding statistical parameters: average, standard deviation, asymmetry coefficient and percentiles. The experimental measurements have established that an asymmetry coefficient and an introduced descriptor– the rank of percentileNeq%are the most sensitive to noise variations. The last one is more preferable due to its exclusive relationships with an equivalent level– the corresponding value of this rank of percentilePNeqthat coincides with the equivalent level of the measured time interval. It has been found that the introduced descriptorNeqis very sensitive for indicating the dissimilarity of environmental noise (the presence of a casual impulse or high energy noise events). In-situ measurements of the vicinity of roads with intensive traffic in Vilnius City, where stationary urban traffic noise is dominating, indicate that the values ofNeqrank obtained during short-term (15÷60 min) intervals in the period from7:00 to 19:00 are stable and vary from 69% to 74%. When non-stability occurs, a significant increase in the values of this descriptor may be applied as criteria for indicating noise events other than traffic noise and may be used for determining the interval limits of short-term stationary measurement. First Published Online: 12 Apr 2011

SummaryIn this paper some known formulae concerning overflow traffic have been derived in a simpler way than is generally done in literature, i.e. by using simple results obtained from elementary renewal theory.After the model has been introduced, the distribution of intervals between overflows is calculated by means of a recurrence relation. A generalization of Erlang's formula for the call congestion follows almost immediately. The last section the special case of Poisson input is discussed.

AbstractThis paper presents a mathematical model of a single‐lane bridge serving two‐way traffic in alternating directions (with an FIFO rule observed within each directional queue). While the bridge serves cars moving in one direction, cars approaching from the opposite direction wait in a queue at its foot. When cars in the current direction finish crossing the bridge, it begins serving cars from the other direction, if any are present. A newly‐arrived car finding an empty bridge mounts it immediately. Several cars moving in the same direction may occupy the bridge simultaneously. The crossing speed is assumed to be constant, and the arrival processes in both directions are assumed to be independent, homogeneous Poisson processes. A generalization of the alternating‐priority models [1, 2] is developed to arrive at the Laplace‐Stieltjes transform and the expected value of the flow time (the time interval between the moments of arrival at the bridge and departure from it) for steady state conditions. The results are discussed and some examples are presented graphically.

Road traffic accidents (RTA) are recognised to be an important cause of death and injury in serving military personnel but little is known about the risk in veterans. We used data from the Scottish Veterans Health Study to examine the risk of RTA in a large national cohort of veterans, in comparison with people who had never served. We conducted a retrospective cohort study of 57,000 veterans and 173,000 non-veterans, followed up for up to 30 years, using survival analysis to compare risk of RTA injury. Subgroup analysis was used to explore trends by birth cohort and length of service. Overall, veterans had a higher risk of RTA (Cox proportional hazard ratio (HR) 1.17, 95% confidence intervals (CI) 1.14–1.20). The risk was highest in the veterans with the shortest service (early service leavers), including those who did not complete initial military training (HR 1.31, 95% CI 1.23–1.40). The mean age at first RTA was 34 years, irrespective of age at leaving service, and the greatest increase in risk was in veterans born in the 1960s, but veterans born after 1970 showed no increase in risk. We have therefore demonstrated that the increased risk of RTA observed in serving military personnel persists in veterans through the fourth decade of life. The high risk in early service leavers is likely to be related to risk factors other than military service, including previous childhood adversity. Recent Ministry of Defence road safety programmes may now be reducing the long-term risk of RTA injury.

Two experiments investigated the performance of air traffic controllers using a simulated Microwave Landing System to control the landing of short takeoff and landing aircraft. In Experiment 1, the task involved the separation of simulated aircraft targets by use of airspeed control. The goal was to ensure that the targets crossed the Missed Approach Point with a specified time interval between them. Experiment 2 employed the same experimental format and task, but the work load was increased by the addition of more targets. Controllers used speed control, radar vectoring, and holding patterns to separate targets. In both experiments, performance was evaluated under no-wind and wind conditions. Significant effects were found due to the configuration of the Microwave Landing System courses and as a result of wind conditions. Performance was generally inaccurate and exhibited high variability. Implications for future development of the Microwave Landing System in the air traffic control system are discussed.

Introduction: The use of leading pedestrian intervals (LPIs) creates safer street crossings for typical pedestrians, giving them a head-start into the crosswalk. The LPI, however, delays the onset of the traditional traffic sound cue that pedestrians who are blind use to initiate crossing streets. LPIs can create situations where pedestrians who are blind will frequently begin or end crossings or both against the pedestrian signal. Methods: The researchers conducted two sets of observations in an urban environment. They measured the seconds from the initiation of the vehicular circular green signal to the front of the first vehicle passing through the center of the intersection (n = 40) to calculate the average driver's delay. Pedestrians who are blind, to confirm a straight-through surge of parallel traffic (i.e. not turning vehicles), listen for a vehicle to reach the roadway center to know it is the appropriate time to initiate a crossing. In the second set of observations (n = 40), the researchers recorded the length of the Walk, Flashing Don't Walk, and LPI to calculate average impacts on crossing. Results: The average time for vehicles to reach the center of the intersection was 6.0 s. When there was an LPI, on average the clearance for pedestrians after reaching the far corner was 0.49 s; for Walk intervals, there was an average of 3.35 s margin of time to begin crossing. Discussion: These observational studies verify the crossing latencies for pedestrians who are blind. At crosswalks with LPI, pedestrians can be expected to cross after the Walk sign has expired 15 to 38% of the time and end their crossing 40 to 82% of the time when the visual display says Don't Walk. Implications for Practitioners: Orientation and mobility specialists should instruct students on how to identify intersections with LPI to assist in decision making. Traffic management remediation is the installation of an accessible pedestrian signal (APS); specialists should advocate for the installation of APS where LPIs are implemented and teach students how to use APS.

Since the emergence of commercial aviation in the early part of last century, economic forces have driven a steadily increasing demand for air transportation. Increasing density of aircraft operating in a finite volume of airspace is accompanied by a corresponding increase in the risk of collision, and in response to a growing number of incidents and accidents involving collisions between aircraft, governments worldwide have developed air traffic control systems and procedures to mitigate this risk. The objective of any collision risk management system is to project conflicts and provide operators with sufficient opportunity to recognize potential collisions and take necessary actions to avoid them. It is therefore the assertion of this research that the currency of collision risk management is time. Future Air Traffic Management Systems are being designed around the foundational principle of four dimensional trajectory based operations, a method that replaces legacy first-come, first-served sequencing priorities with time-based reservations throughout the airspace system. This research will demonstrate that if aircraft are to be sequenced in four dimensions, they must also be separated in four dimensions. In order to separate aircraft in four dimensions, time must emerge as the primary tool by which air traffic is managed. A functional relationship exists between the time-based performance of aircraft, the interval between aircraft scheduled to cross some three dimensional point in space, and the risk of collision. This research models that relationship and presents two key findings. First, a method is developed by which the ability of an aircraft to meet a required time of arrival may be expressed as a robust standard for both industry and operations. Second, a method by which airspace system capacity may be increased while maintaining an acceptable level of collision risk is presented and demonstrated for the purpose of formulating recommendations for procedures regulating air traffic management methods and industry standards governing performance requirements for avionics designed to support trajectory based operations.

Access management, which systematically limits opportunities for egress and ingress of vehicles to highway lanes, is critical to protect trillions of dollars of current investment in transportation. This article addresses allocating resources for access management with incomplete and partially relevant data on crash rates, travel speeds, and other factors. While access management can be effective to avoid crashes, reduce travel times, and increase route capacities, the literature suggests a need for performance metrics to guide investments in resource allocation across large corridor networks and several time horizons. In this article, we describe a quantitative decision model to support an access management program via risk‐cost‐benefit analysis under data uncertainties from diverse sources of data and expertise. The approach quantifies potential benefits, including safety improvement and travel time savings, and costs of access management through functional relationships of input parameters including crash rates, corridor access point densities, and traffic volumes. Parameter uncertainties, which vary across locales and experts, are addressed via numerical interval analyses. This approach is demonstrated at several geographic scales across 7,000 kilometers of highways in a geographic region and several subregions. The demonstration prioritizes route segments that would benefit from risk management, including (i) additional data or elicitation, (ii) right‐of‐way purchases, (iii) restriction or closing of access points, (iv) new alignments, (v) developer proffers, and (vi) etc. The approach ought to be of wide interest to analysts, planners, policymakers, and stakeholders who rely on heterogeneous data and expertise for risk management.