This research theme investigates the concepts of safety targets and target-setting, reviews the current experience in safety-critical industries and uses this information to develop methods appropriate to each mode of transport. This is followed by the development of methods for the application of safety targets and the means to monitor/track performance against set targets. The outputs of this research theme feed into the other three themes that are in the focus of the LRF TRMC.

Research projects


Modelling Airport Surface Safety

Research Project: Modelling Airport Surface Safety


The steady growth in air traffic has been one of the major features in transportation over the last 50 years and forecasts indicate a further growth for at least the next twenty years. In addition to problems associated with congestion and delays, this growth has considerable safety impacts. One major area highlighted by a number of aviation authorities is that of airport surface safety, in particular runway and taxiway safety.

Although previous and current initiatives increasingly emphasize this topic, the industry is characterized by a piecemeal approach and surface safety rarely considered in an integrated manner. To address this issue, this research proposes to develop a model of airport surface safety.


Airport operationsAs a first step, a theoretical model of normal airport surface operations is developed. Subsequently, a global study of the critical factors that underlie airport surface accidents and incidents (occurrences) is conducted, and used to develop a new holistic taxonomy of causal and contributing factors. The taxonomy incorporates the viewpoint of all relevant aviation stakeholders (regulators, Air Navigation Service Providers, airlines, airport operators,ground handling companies, Accident Investigation Boards) involved in the subject matter. Its robustness is facilitated by the application of different research methods (literature, multi-national safety data analysis, airportssurvey, interviews). In a thirst step, statistical analysis is used to identify the impact of airport characteristics (e.g. airfield geometry, level of equipment, operations) on safety occurrences. Airports can then be categorized in terms of airport surface risk.

The final model of airport surface safety assesses the functional relationship between accidents and incidents and their underlying critical factors in order to outline effective safety mitigation strategies. The model considers the viewpoints of all relevant aviation stakeholders and accounts for data quality issues (i.e. weighting of different databases). All models are validated through accident/incident data and observational data at selected representative US and European airports.

Collaborations / Project Partners

Data was provided by the UK Civil Aviation Authority (UK CAA), Federal Aviation Administration (FAA), New Zealand CAA (NZ CAA), Avinor, OSL Lufthavn, Norwegian A/S, Signature Flight Support and easyJet. The results have been validated with subject matter experts from EUROCONTROL and the FAA.


  1. Wilke, S., Majumdar, A. and W.Y. Ochieng (2012) A Holistic Approach toward Airport Surface Safety, Transportation Research Record: Journal of the Transportation Research Board, Washington D.C., USA, (accepted).
  2. Wilke, S. and A. Majumdar (2012) Critical factors underlying airport surface accidents and incidents: A holistic taxonomy, Journal of Airport Management, 6 (2), pp. 170-190.
  3. Wilke, S., Majumdar, A., and W.Y. Ochieng (2012), Assessing the quality of aviation safety databases: An external data validation framework, 5th International Conference on Research in Air Transportation — ICRAT 2012, University of California, Berkley, 22-25 May 2012.
  4. Wilke, S., Majumdar, A. and W.Y. Ochieng (2012) A holistic approach towards airport surface safety, Transportation Research Board – 91st Annual Meeting. Washington, D.C. USA, Jan 22-26 2012.
  5. Wilke, S., Majumdar, A. and W.Y. Ochieng (2011) Analysis of critical factors underlying airport surface safety occurrences – A global comparison, 1st Conference of Transportation Research Group of India (CTRG). Bangalore, India, Dec 7-10 2011.
  6. Wilke, S. and Majumdar, A. (2011), A multi-national causal analysis of airport surface safety occurrences, 11th AIAA Aviation, Technology, Integration, Operations (ATIO) Conference. Virginia Beach, USA, Sep 21-22, 2011.
  7. Wilke, S., Majumdar, A., and W.Y. Ochieng (2011), The potential of automation to improve airport surface safety, 1st International Conference on Application and Theory of Automation in Command and Control Systems (ATACCS), Barcelona, Spain, 26-27 May 2011.

Air Traffic Networks

Research Project: Optimisation of the European Air Traffic Network


The European Commission has passed two Single European Sky packages (SES & SES II) to create a legislative framework for European aviation and to meet future capacity and safety objectives. The main strategy to increase European airspace capacity is to reorganize the airspace from sixty-seven fragmented areas according to national borders into nine functional airspace blocks (FAB) designed for better utilization of air traffic flow management. The capacity constraints caused by national boundaries will be reduced by implementation of FABs, and the efficiency of air traffic flows and air navigation service provision will be improved by the integrated services providers.

A key enabler to enhance the airspace capacity is to improve the “ATM Network functions” for an optimal utilization of European airspace. The Network functions will be a fundamental enabler for the safe and efficient provision of services in the European ATM network, which includes a considerable number of airspace users, airports, and air navigation service providers. The role of Network Management is considered a central element to coordinate with airspace users, airports and air navigation service providers to deliver better service with satisfactory performance in European airspace. The fragmentation of national systems and the limitations of air traffic control technologies and operational procedures are the main constraints for achieving the enhanced efficiency and increasing capacity in the future.


The current methods of capacity estimation focus at the local level, such as airport capacity, en-route capacity and air traffic controllers’ workload and need to be improved to accommodate the changed concept of future ATM system. Various measures are being adopted and legislated to increase the European airspace capacity to accommodate the growing air traffic demand in European airspace. Whilst challenging, it is essential to assess and estimate both the capabilities of different components and the overall network of the air traffic system to support any traffic increases. The integrated approach to estimate the capacity of airspace is a challenging task in support of any traffic increases in the future. Furthermore, it is expected that the capability of assessing network capacity of the European ATM system will be developed in this research, with specific objectives are:

  1. Detailed review of related knowledge and document of European air traffic management, such as the SES Concepts of Operation, the functional and physical architecture of SESAR;
  2. To identify and create the framework of network of European ATM system;
  3. To develop a model to assess the network capacity;
  4. To validate the assessment model.


This PhD project is sponsored by the Ministry of National Defence, R.O.C. (Taiwan).

Climate Change

A Framework to mitigate Aviation’s Climate Change Impact in the European Union


In Europe, long-term aviation growth is forecast and with its CO2 emissions growing faster than other economic sectors, pressure is increasing on the industry to manage its environmental impact. Although the aviation industry is keen to point out that the global industry only accounts for 2% of global CO2 emissions, it rarely acknowledges the reality that total global CO2 emissions are also increasing, with the implication that its contribution is increasingly significant. The International Energy Agency (IEA) reports that production of conventional oil is projected to peak in the 2020s. This will have profound implications for all sectors of the European economy and in particular the aviation industry. Past research has shown that some of the options currently available for the industry to mitigate its environmental impact and in particular CO2 emissions are complex, expensive, and take time to implement. Furthermore, the current methods are unlikely to be enough for the industry to achieve the required reduction in CO2 emissions. Therefore, significant challenges lie ahead for policymakers and industry leaders.


This research investigates the aviation industry’s environmental impact, focusing on its CO2 emissions in the context of climate change. It takes a three-step approach, starting with a literature review based investigation of the mitigation initiatives that have been used for some time in parts of the industry, and discovers the barriers to their widespread and full implementation across the industry. The scope of existing measures explored and appraised includes policy, regulation, institutional aspects, management and technology. In addition, the role for improved environmental assessment is developed in the form of an environment case. The literature based investigation is augmented in a second step by a targeted international survey of aviation stakeholders on their perspectives on the industry’s environmental impact, mitigation, regulatory framework, barriers to change and best practice. Two significant findings emerge from this. Firstly, many stakeholders tend to be critical of each other, regulators, policymakers and the slow pace of reform. This suggests that any reform and change in the industry should be thought through carefully facilitated by effective dialogue with stakeholders. Secondly, despite the current focus on Air Traffic Management (ATM), technology, policy and airspace reforms and initiatives, these measures are not enough to deliver the necessary absolute CO2 emission reductions given the projected growth of the industry.

From the results of the first two steps above, a third investigates the potential role of demand management and economic instruments. Based on aviation demand elasticity, calculated using a new database, it is shown that in order for the aviation industry to meet Europe’s CO2 emission targets and climate policies, current and proposed measures should be maximised and used together with demand management.


This thesis was awarded a PhD in March 2011.

Molloy, J., Melo, P.C., Graham, D.J., Majumdar, A. and W.Y. Ochieng (2012) The Role of Air Travel Demand Elasticities in Reducing Aviation's CO2 Emissions: Evidence for European Airlines, Transportation Research Record: Journal of the Transportation Research Board, Washington D.C., USA, (accepted).

Molloy, J. and A. Majumdar (2011) Evaluating Aviation Stakeholder's Perspectives On Climate Change: The Experience From Europe, Proceedings of the Transportation Research Board 90thAnnual Meeting. Washington D.C., USA, Jan 23-27 2011.


Safety management systems

Development of a Data Quality Index for Safety Management Information Systems in Railways


Safety Management Systems (SMS) in railways as well as other industries are fundamental to gather information about safety critical incidents and accidents. They provide the basis for safety analysis and risk modeling that is used for diverse strategic and operational decisions e.g. maintenance planning. SMS collect a wide range of accident and incident datasets from one or numerous railway operators.

These datasets are not necessarily entered by organisations or data analysts with the same understanding of safety and safety management processes. Consequently this affects the quality of  data values, its integration and comparability. Likewise data quality issues lead to uncertainties within safety and risk models and weaken the validity.

In order to assess the quality of datasets within a SMS among different accident types and operators, data quality dimensions and indicators need to be defined, measured, analysed and subsequently improved. Herewith, the validity of safety data can be ensured and sources of uncertainties may be adressed. Moreover, safety managers can identify areas of improvement for safety management processes, the safety culture and reporting mechanisms.

Approach / Methodology

This study contemplates the Safety Management Information System (SMIS) operated by the Railway Safety Standards Board (RSSB) in Great Britain. It aims to define data quality dimensions and measures for safety management information and to propose a model of influential factors that are relevant for the railway industry and other industries dealing with SMS. The study provides insights into data quality of empirical datasets on workforce assaults from 2010 to 2012 and compares the subjective perceptions of data quality of 28 transport operators for the same datasets. These subjective perceptions are gathered by a comprehensive interview series among the British transport operators in 2012. These datasets are integrated into a data quality index for the British railway industry using an Analytical Hierarchy Process.

The research thereby gives new insights into the determinants of data quality within safety management systems. It provides a first methodological approach how to measure and compare data quality and identifies areas of improvement. Furthermore, the research project benefits from its conjunctive quantitative and qualitative approach as well as its integration of different research disciplines; such as railways, safety, information and quality management.