David Pitfield

Methodology for predicting European short-haul air transport demand from regional airports

This work uses data from Civil Aviation Authority surveys to develop a methodology to model air trip generation within the Midlands region and air trip distribution between available airports. The technique applied in the modelling of air trip generation is that of propensity to fly, whereby the trip-making population are categorized both spatially and according to standard industrial classification for business trips and socioeconomic group for leisure trips. By estimation of growth rates in propensities to fly a new distribution of trip origins can be produced for the forecasting year. Distribution of these trips between East Midlands, Birmingham, Heathrow, Manchester and Leeds/Bradford airports is made using a model of the multinomial logit form. The explanatory variables contained within the model are access time, a frequency utility function which gives a diminishing marginal utility with respect to flight frequency, cost and an aircraft technology dummy variable, distinguishing services operated by jet and those operated by turboprop aircraft. Of these variables, flight frequency contributes most to overall utility. The approach allows forecasts to be made of market share under a variety of supply scenarios, greatly assisting in the decision-making of management and policy-makers.

A MONTE-CARLO SIMULATION OF POTENTIALLY CONFLICTING GROUND MOVEMENTS AT A NEW INTERNATIONAL AIRPORT

Plans for a large new international airport propose that aircraft in need of maintenance must be towed to facilities across active aprons. An investigation is carried out for peak hour traffic of the likely amount of conflict between towed aircraft and arriving and departing aircraft. On the basis of reasonable assumptions and some known statistics, a statistical experiment using Monte-Carlo simulation is carried out to demonstrate that, contrary to first intuitive impressions, the amount of conflict, both in terms of the number of holds and the mean holding time, is low.

Monte Carlo comes to Rome: a note on the estimation of unconstrained runway capacity at Rome Fiumucino International Airport

A new airport capacity concept has been advanced by the International Air Transport Association (IATA). Unconstrained capacity represents the airport capacity with reservoirs of traffic always available and the use of all planned technological and air traffic managerial improvements. To establish its utility and estimate its value for the first time, the case of Rome Fiumucino International Airport is examined.

Re-visiting crash-speed relationships: a new perspective in crash modelling

Although speed is considered to be one of the main crash contributory factors, research findings are inconsistent. Independent of the robustness of their statistical approaches, crash frequency models typically employ crash data that are aggregated using spatial criteria (e.g., crash counts by link termed as a link-based approach). In this approach, the variability in crashes between links is explained by highly aggregated average measures that may be inappropriate, especially for time-varying variables such as speed and volume. This paper re-examines crash-speed relationships by creating a new crash data aggregation approach that enables improved representation of the road conditions just before crash occurrences. Crashes are aggregated according to the similarity of their pre-crash traffic and geometric conditions, forming an alternative crash count dataset termed as a condition-based approach. Crash-speed relationships are separately developed and compared for both approaches by employing the annual crashes that occurred on the Strategic Road Network of England in 2012. The datasets are modelled by injury severity using multivariate Poisson lognormal regression, with multivariate spatial effects for the link-based model, using a full Bayesian inference approach. The results of the condition-based approach show that high speeds trigger crash frequency. The outcome of the link-based model is the opposite; suggesting that the speed-crash relationship is negative regardless of crash severity. The differences between the results imply that data aggregation is a crucial, yet so far overlooked, methodological element of crash data analyses that may have direct impact on the modelling outcomes.

The normalisation of aircraft overrun accident data

This paper is concerned with normalising runway overrun aircraft accident data so as to allow all accident data to be properly relevant to any overrun accident investigation. This task is part of a wider research task that addresses the need for models to assess the risk of aircraft operations at any particular airport based on risk management principles and to use all available data on previous accidents. The case of runway overruns is taken because new regulations require consideration of the provision of much longer Runway End Safety Areas than had been previously the norm. The reported research collects accident data and then describes its normalisation based on corrections made due to the effects of terrain, aircraft performance and required distances on the accident locations.

Exploring the factors affecting motorway accident severity in England using the generalised ordered logistic regression model

PROBLEM The severity of motorway accidents that occurred on the hard shoulder (HS) is higher than for the main carriageway (MC). This paper compares and contrasts the most important factors affecting the severity of HS and MC accidents on motorways in England. METHOD Using police reported accident data, the accidents that occurred on motorways in England are grouped into two categories (i.e., HS and MC) according to the location. A generalized ordered logistic regression model is then applied to identify the factors affecting the severity of HS and MC accidents on motorways. The factors examined include accident and vehicle characteristics, traffic and environment conditions, as well as other behavioral factors. RESULTS Results suggest that the factors positively affecting the severity include: number of vehicles involved in the accident, peak-hour traffic time, and low visibility. Differences between HS and MC accidents are identified, with the most important being the involvement of heavy goods vehicles (HGVs) and driver fatigue, which are found to be more crucial in increasing the severity of HS accidents. PRACTICAL APPLICATIONS Measures to increase awareness of HGV drivers regarding the risk of fatigue when driving on motorways, and especially the nearside lane, should be taken by the stakeholders.

The derivation and analysis of the passenger peak hour: an empirical application to Brazil

Many different definitions are currently used to define a design `peak’ hour at airports, such that the majority of passengers receive adequate service levels and only an acceptably small proportion experience the impact of congestion. The evaluation of level of service provision depends on this definition. Previous definitions have either used a nominal hour below the absolute peak or have taken a representative hour from the schedule of flights. This paper endeavours to define this level of traffic empirically. Data for 48 Brazilian airports covering a five-year period are analysed to develop a methodology for and determine the appropriate peak hour for design standards. This empirically derived traffic level is regressed against annual traffic levels to establish a relationship that should enable the forecast of design peak hour demand with changing annual throughputs.

Predicting the safety impact of a speed limit increase using condition-based multivariate Poisson lognormal regression

ABSTRACT Speed limit changes are considered to lead to proportional changes in the number and severity of crashes. To predict the impact of a speed limit alteration, it is necessary to define a relationship between crashes and speed on a road network. This paper examines the relationship of crashes with speed, as well as with other traffic and geometric variables, on the UK motorways in order to estimate the impact of a potential speed limit increase from 70 to 80 mph on traffic safety. Full Bayesian multivariate Poisson lognormal regression models are applied to a data set aggregated using the condition-based approach for crashes by vehicle (i.e. single vehicle and multiple vehicle) and severity (i.e. fatal or serious and slight). The results show that single-vehicle crashes of all severities and fatal or serious injury crashes involving multiple vehicles increase at higher speed conditions and particularly when these are combined with lower volumes. Slight injury multiple-vehicle crashes are found not to be related to high speeds, but instead with congested traffic. Using the speed elasticity values derived from the models, the predicted annual increase in crashes after a speed limit increase on the UK motorway is found to be 6.2–12.1% for fatal or serious injury crashes and 1.3–2.7% for slight injury, or else up to 167 more crashes.

The economics of airport impact

This paper categorizes the economic impacts of airport construction and operation and outlines methodologies that are available to assess the magnitude of these impacts. A review of empirical studies suggests that existing methodologies are not always well used and that certain gaps in our knowledge make the article of faith that airports always significantly affect economic growth questionable. This paper was initially prepared for the INTRODUCTION TO AIRPORT DESIGN Short Course held at Loughborough University of Technology, 10th–14th December, 1979 and was later presented to a seminar at the Institute of Transportation Studies, University of California, Berkeley. The contribution of both these meetings to the present paper is acknowledged.

AN INTRAMAX DERIVATION OF COMMODITY MARKET AREAS FROM FREIGHT FLOW DATA

This paper describes the use of a functional regionalisation procedure in partitioning a series of commodity flow matrices. The applications serve to highlight a number of issues that are raised in the interpretation of the flow structures and patterns of interrelationships between areas that emerge from the analysis. In particular, the paper illustrates the problems that are encountered in attempting to both distinguish and summarise the similarities and differences that are observed in the configuration and extent of commodity market areas. The results underline the need to devise measures that enable the measurement of the degree of difference or similarity between a series of grouping structures that are produced by a hierarchical grouping procedure of the type employed here.