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1.
This paper examines wildlife strikes with civil helicopters within the US. Month and time of day, location, and other factors influenced the frequency of wildlife strikes with civil helicopters. Wildlife strikes occurred most frequently when the aircraft were traveling en route or engaged in terrain flight. Birds accounted for over 97% of the wildlife strikes where the animal was identified. 相似文献
2.
The objective of this paper is to investigate the impact of pre-trip information on auto commuters’ choice behavior. The analysis is based on an extensive home-interview survey of commuters in the Taichung metropolitan area in Taiwan. A joint model for route and departure time decisions with and without pre-trip information is formulated. The model specifications are developed for both the systematic and random components. In particular, econometric issues associated with specifying the random error structure are addressed for parameter estimation purposes. Insights into the effects of attributes are obtained through the analysis of the model's performance and estimated parameter values. A probit model form is used for the joint model, allowing the introduction of state dependence and correlation in the model specification. The results underscore the important relationship between the different characteristics and the propensity of commuter choice behavior under two scenarios, with and without pre-trip information. 相似文献
3.
Road crashes are a leading cause of death and serious injuries both developed and developing countries. Intersections are recognized as being among the most hazardous locations on the roads. Although crashes at intersections form about 35 % of the reported accidents account for about 32% of traffic‐related serious injuries and fatalities in Singapore, there is no known study that examines the factors contributing to the severity of these crashes. In this study, the ordinal probit model was applied to crash data from 1992 to 2002 to investigate the role a variety of factors play in determining the severity of intersection crashes. Our study shows that vehicle type, road type, collision type, driver's characteristics and time of day are important determinants of the severity of crashes at intersections in Singapore. 相似文献
4.
Aircraft mass is a crucial piece of information for studies on aircraft performance, trajectory prediction, and many other topics of aircraft traffic management. However, It is a common challenge for researchers, as well as air traffic control, to access this proprietary information. Previously, several studies have proposed methods to estimate aircraft weight based on specific parts of the flight. Due to inaccurate input data or biased assumptions, this often leads to less confident or inaccurate estimations. In this paper, combined with a fuel-flow model, different aircraft initial masses are computed independently using the total energy model and reference model at first. It then adopts a Bayesian approach that uses a prior probability of aircraft mass based on empirical knowledge and computed aircraft initial masses to produce the maximum a posteriori estimation. Variation in results caused by dependent factors such as prior, thrust and wind are also studied. The method is validated using 50 test flights of a Cessna Citation II aircraft, for which measurements of the true mass were available. The validation results show a mean absolute error of 4.3% of the actual aircraft mass. 相似文献
5.
In this paper, we aim to estimate the effect of contract renewal as well as competitive tendering on public transport costs, subsidies, and ridership. More specifically, we examine to what extent (multiple) contract renewals and introduction of competitive tendering for long-term public transport contracts affect ridership, operational costs and subsidies in concession areas governed by public transportation authorities from 2001 until 2013 in the Netherlands. Our identification strategy improves on the literature as we are able to control for all time-invariant unobserved factors, such as network and area characteristics by using panel data. We show that when renewing long-term contracts, operational costs are reduced by at least 10%, whereas subsidies fall even stronger. For contracts that are renewed at least twice, the reduction in costs is even more substantial and in the order of 16%. We find that the effect of competitive tendering is completely absent, suggesting that the threat of competitive tendering is sufficient in a market where the majority of concessions is competitive tendered. Contract renewal not only reduces costs and subsidies, but simultaneously increases public transport ridership by 7.7%. Furthermore the vehicle-hours elasticity of operational costs is 0.40, pointing to strong economies of density. The geographical scale elasticity of operational costs is around one, which indicates constant returns to scale with respect to the geographical size of the concession area. This suggest that the current size of the Dutch concession area is optimal with respect to costs. 相似文献
6.
Abstract The purpose of this study was to investigate the impact of the five strikes on the London Underground (metro) rail system, which occurred in 2009 and 2010, on macroscopic and road link travel times. A consequence of these strikes was an increase in road traffic flows above usual levels. This provides an opportunity to observe the operation of the road network under unusually high flows. The first objective involves the examination of strike effects on inbound (IT) and outbound traffic (OT) within central, inner and outer London. Travel time data obtained from automatic number plate recognition cameras are used within the first part of the analysis. The second more detailed objective was to investigate in spatio-temporal effects on travel times on five road links. Correlation analyses and general linear models are developed using both traffic flow and travel time data. According to the results of the study, the morning IT had approximately twice as much delay as the OT. Central London experienced the highest delays, followed by inner and outer London. As would be expected, the unique full-day strike in 2009 yielded the worst impact on the network with the highest percentage increase in total travel time (60%) occurring during the morning peak in the IT in inner London. The results from the link-level analysis showed statistical significance amongst the examined links indicating heterogeneous effects from one link to another. It was also found that travel time changes may be more effectively captured through time-of-day terms compared to hourly traffic flows. 相似文献
7.
The paper outlines the theoretical underpinnings of an urban mass transit revenue and ridership model designed to provide medium term forecasts of future trends in situations of data sparsity. The specific example laid out in the paper relates to the Greater Vancouver Regional District but the framework is of general applicability. Much of the informational input at the initial stage is of a general kind and details of the specific transit system and local area are of the sort which should be readily available to most urban authorities. The model developed is designed for use on a desk‐top micro‐computer and offers an inter‐active method of forecasting. The operator has the facility to both consider fare policy sensitivity and review alternative scenarios about future trends in exogenous factors. A selection of forecasts developed for the GVRD is provided to reveal the main features of the approach. 相似文献
8.
Giovanni Nero John A. Black 《Transportation Research Part D: Transport and Environment》2000,5(6):433-461
In the wake of the Australian airline liberalization in 1990 and its forecasted impact on air traffic, capacity has been expanded at Sydney (Kingsford Smith) airport (Sydney KSA) – Australia's busiest commercial airport – with the construction of the third runway in 1994. Coinciding with the approval for this capacity expansion, the Commonwealth Government amended the Federal Airports Corporation (FAC) Act to direct the FAC to carry out activities which protect the environment from the effects of aircraft operations, with the cost to be borne by the airline industry according to the ‘Polluter Pays Principle'. Noise management plans were part of the conditions for developmental approval for a third runway. To this end, since 1995, Sydney KSA imposes a noise levy designed to generate sufficient revenues to fund a noise mitigation scheme. Although the issues of aircraft noise, in particular its impact on property values and land use planning around the airport, have been extensively addressed in the literature, no one has empirically examined the implications of new environmental policies in conjunction with airline liberalization and change in airport infrastructure. Principles and policy analyses are discussed in this paper. By focusing on the specifics of Sydney KSA, broader policy issues likely to be relevant for other major airports around the world are discussed. 相似文献
9.
It is widely known that emissions from aircraft engines, Auxiliary Power Units (APU) and ground handling equipment contribute to air pollution at airports. During the aircraft turnaround process, the main source of emissions is the APU. The use of the APU can be significantly reduced if the aircraft stand is equipped to supply external electrical power and pre-conditioned air to the cabin. This paper analyses the actual duration of APU and external power usage during intraday aircraft turnarounds at 125 airports during June 2015. The data is derived from flight data recording units of more than 200 short-haul, narrow-body jet aircraft, conducting some 25,195 aircraft turnarounds and thus provides the most detailed assessment of aircraft power usage available. A common practice is for the APU to be running for a short period on arrival at the stand (arrival-cycle) and then again for a short period prior to departure (departure-cycle). It is identified in this study that departure-cycle emissions are three times greater than arrival-cycle emissions. These emissions could be reduced if more accurate forecasts of departure times are available to flight crew. The provision of external ground power is found to reduce emissions by up to 47.6%. However, the study also highlights that when the source of external power is a diesel-fuelled mobile Ground Power Unit (GPU), there is a net doubling in emissions of hydrocarbons. APU usage is also observed to vary with outside air temperature (OAT) leading to possible increases in emissions of up to 6%. 相似文献
10.
Accurate prediction of aircraft position is becoming more and more important for the future of air traffic. Currently, the lack of information about flights prevents us to fulfill future demands for the needed accuracy in 4D trajectory prediction. Until we get the necessary information from aircraft and until new more accurate methods are implemented and used, we propose an alternative method for predicting aircraft performances using machine learning from historical data about past flights collected in a multidimensional database. In that way, we can improve existing applications by providing them better inputs for their trajectory calculations. Our method uses flight plan data to predict performance values, which are suited individually for each flight. The results show that based on recorded past aircraft performances and related flight data we can effectively predict performances for future flights based on how similar flights behaved in the past. 相似文献
11.
In this paper we describe the methods used to develop the open source Aviation Emissions Inventory Code and produce a global emissions inventory for scheduled civil aviation, with quantified uncertainty. We estimate that in 2005, scheduled civil aviation was responsible for 180.6 Tg of fuel burn, which agrees to within 4% of other published emissions inventories for 2004 and 2006. By comparing the Aviation Emissions Inventory Code with flight data records, we show that the mean bias in predicted fuel burn at the airport-pair level is +1% for an ensemble of 132 flights, and less than 10% for 5 of the 6 aircraft types used in the validation. 相似文献
12.
Wildlife incidents with aircraft are of concern in the United States as they pose a risk to human safety and economic losses for the aviation industry. Most previous research on wildlife-aircraft incidents has emphasized birds, bats, and ungulates. We queried the Federal Aviation Administration’s National Wildlife Strike Database from 1990 to 2012 to characterize carnivore incidents with U.S. civil aircraft. We found 1016 carnivore incidents with aircraft representing at least 16 species, with coyotes (n = 404) being the species most frequently struck. California and Texas had the most reported incidents and incidents were most likely to occur at night from August to November. Overall estimated damage to aircraft was US$ 7 million. Coinciding with the increase in air traffic, the rate of carnivore-aircraft incidents increased 13.1% annually from 1990 to 2012 whereas the rate of damaging incidents remained fairly constant. Due to the increase in carnivore-aircraft incidents from 1990 to 2012, we recommend further research on techniques to increase detection of carnivores and implementation and scheduled maintenance of perimeter high fences for exclusion. Additionally, we recommend increasing patrol of runways, especially during peak incident periods (July–November) and at night (2000–0600 h). 相似文献
13.
This study looks at the singling out of a multi-parameter criterion for choosing conventional or innovative roundabout layouts, by taking functional, environmental and economic aspects into consideration. The performances of three conventional roundabouts (with different lane number at entries and through the ring), turbo-roundabouts and roundabouts with right-turn bypass lane on all the arms (flower roundabouts) have been compared in terms of vehicle delays and pollutant (carbon dioxide, nitrogen oxides, particle pollution (PM10 and PM2.5)) emissions. By means of closed-form capacity models and with the help of COPERT IV© software, several traffic simulations have been carried out, referred to yearly peak flow values Qmax and ranging between 1300 and 3300 veh/h, starting from a typical annual traffic demand curve in urban areas. The estimation of cumulative vehicle delays and annual pollutant emissions, together with construction and maintenance costs has allowed working out overall costs for each roundabout under consideration, depending on the traffic demand. Thus, the proposed model allows finding the most cost-effective geometric solution as to overall costs for a comprehensive case record of traffic values. 相似文献
14.
The rapid development of road infrastructure is inevitable with increasing world human population and rise in the number of vehicles on the roads is going to be an increasing threat to native habitat of many wildlife populations around the world. The present work examines the edge effect of high traffic roads on nest site selection of birds in Udaipur city, Rajasthan (India). A total of 112 nesting site of 14 bird species (among six guilds), was recorded during the study. All six guilds (i.e., carnivore, omnivore, granivore, nectivore, frugivore and insectivore) were sharing similar kind of habitat with fine scale differences (P < 0.0001). The PCA revealed that trees with suitable GBH, canopy and height were supporting birds’ nesting diversity, but the buildings were supporting the highest number of nesting. Different guilds showed different preference to different variables. Spatial heterogeneity, less predation, optimal feeding ground and higher number of advertising and display boards of shops at roadside buildings might be crucial factors for birds’ nesting in this highly disturbed area. 相似文献
15.
A reasonable boarding model can effectively improve the boarding efficiency. Therefore, developing boarding models/strategies to improve the boarding efficiency has been an interesting topic in the air transportation. In this paper, we incorporate the group behavior and the quantity of luggage into the boarding process, and then develop an extended boarding model to investigate the effects of the two factors on the delay time and boarding time. The numerical results show that the quantity of luggage may make each passenger’s boarding behavior more complex, while the group behavior can shorten some passengers’ delay time and the total boarding time. The results can help administrators organize the boarding process and enhance the boarding efficiency. 相似文献
17.
Aircraft boarding is a process mainly impacted by the boarding sequence, individual passenger behavior and the amount of hand luggage. Whereas these aspects are widely addressed in scientific research and considered in operational improvements, the influence of infrastructural changes is only focused upon in the context of future aircraft design. The paper provides a comprehensive analysis of the innovative approach of a Side-Slip Seat, which allows passengers to pass each other during boarding. The seat holds the potential to reduce the boarding time by approx. 20%, even considering operational constraints, such as passenger conformance to the proposed boarding strategy. A validated stochastic boarding model is extended to analyze the impact of the Side-Slip Seat. The implementation of such fundamental change inside the aircraft cabin demands for adapted boarding strategies, in order to cover all the benefits that accompany this new dynamic seating approach. To reasonably identify efficient strategies, an evolutionary algorithm is used to systematically optimize boarding sequences. As a result, the evolutionary algorithm depicts that operationally relevant boarding strategies implementing the Side-Slip Seat should differentiate between the left and the right side of the aisle, instead of the current operationally preferred boarding from the back to the front. 相似文献
18.
This research analyses the environmental footprint of the airline industry in an attempt to highlight potential paths for improvement. We develop a directional economic-environmental distance function (DEED) which accounts for the production of both desirable and undesirable output and the potential for constrained increases in input utilization. This research applies the modeling framework to analyze the potential to reduce noise and airborne pollutants emitted by aircraft–engine combinations given the current state of aeronautical technology. The global aircraft–engine market is viewed from the regulatory perspective in order to compare the single environmental and operational efficient frontier to that of the airline carriers, and environmental objectives. The results of DEED are then applied in order to substitute the fleets serving Schipol, Amsterdam and Arlanda, Stockholm airports in June 2010 with the benchmark aircraft. The results highlight the inefficiencies of the current airline fleets and that the IPCC values of externalities are a magnitude of TEN too low to encourage changes in the global fleet hence the need for government intervention. 相似文献
19.
This study focuses on how to use multiple data sources, including loop detector counts, AVI Bluetooth travel time readings and GPS location samples, to estimate macroscopic traffic states on a homogeneous freeway segment. With a generalized least square estimation framework, this research constructs a number of linear equations that map the traffic measurements as functions of cumulative vehicle counts on both ends of a traffic segment. We extend Newell’s method to solve a stochastic three-detector problem, where the mean and variance estimates of cell-based density and flow can be analytically derived through a multinomial probit model and an innovative use of Clark’s approximation method. An information measure is further introduced to quantify the value of heterogeneous traffic measurements for improving traffic state estimation on a freeway segment. 相似文献
20.
This paper deals with developing a methodology for estimating the resilience, friability, and costs of an air transport network affected by a large-scale disruptive event. The network consists of airports and airspace/air routes between them where airlines operate their flights. Resilience is considered as the ability of the network to neutralize the impacts of disruptive event(s). Friability implies reducing the network’s existing resilience due to removing particular nodes/airports and/or links/air routes, and consequently cancelling the affected airline flights. The costs imply additional expenses imposed on airports, airlines, and air passengers as the potentially most affected actors/stakeholders due to mitigating actions such as delaying, cancelling and rerouting particular affected flights. These actions aim at maintaining both the network’s resilience and safety at the acceptable level under given conditions.Large scale disruptive events, which can compromise the resilience and friability of a given air transport network, include bad weather, failures of particular (crucial) network components, the industrial actions of the air transport staff, natural disasters, terrorist threats/attacks and traffic incidents/accidents.The methodology is applied to the selected real-life case under given conditions. In addition, this methodology could be used for pre-selecting the location of airline hub airport(s), assessing the resilience of planned airline schedules and the prospective consequences, and designing mitigating measures before, during, and in the aftermath of a disruptive event. As such, it could, with slight modifications, be applied to transport networks operated by other transport modes. 相似文献