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How can Systems Engineering help foster an improved transport system in the UK? This blog series will examine how transport systems use Systems Engineering and how Systems Engineering will be essential for their future success.

‘The Whole System’ is a series (or a system, if you will) of blog posts covering Systems Engineering (SE) in transport. It will provide a snapshot of how SE works within the wide range of transport modes we now take for granted.

Systems Engineering defined

These definitions provided by the International Council on Systems Engineering (INCOSE) are a good guide to what the discipline entails: 

  • system is an arrangement of parts or elements that together exhibit behaviour or meaning that the individual constituents do not.
  • An engineered system is a system designed or adapted to interact with an anticipated operational environment to achieve one or more intended purposes while complying with applicable constraints.
  • Systems Engineering is a transdisciplinary and integrative approach to enable the successful realisation, use, and retirement of engineered systems, using systems principles and concepts, and scientific, technological, and management methods
  • Thus, an “engineered system” is a system – not necessarily a technological one – which has been or will be “systems engineered” for a purpose.

International Council on Systems Engineering (INCOSE) website

This definition is important because it spans the engineering and technology disciplines. It underlines the fact that that an engineered system exists to meet a need or a set of needs.

For anyone unfamiliar with Systems Engineering, it is worth going back to basic principles. A system begins with a collection, a set. Representing this within a Venn diagram, items are identified together (within a boundary) because they are part of the same collection. It is possible for those elements to belong to more than one collection at the same time.

The collection and the relationships between its elements are the foundation of the system, which must contain at least two related elements. Physical systems, such as a car engine or a laptop computer, will exhibit emergent behaviours, which accomplish tasks in time, that the parts alone could not achieve. The system is distinguished according to its behaviours. This is the basis of Systems Engineering (SE), identifying the elements of interest and understanding how they relate to each other.

San Francisco, United States, 2018 Source: Hannah Grace, Unsplash

It's complicated…or complex

A ‘complex’ system is one that is highly connected and inter-related, where the parts are multi-functional, and knowing the individual elements will not provide an understanding of the whole system. Such systems are often difficult to understand or predict because so many of their behaviours are emergent and not reducible to the properties of individual elements.

Complex systems, such as living organisms or the transport systems that connect societies, are particularly challenging to predict because of uncertain relationships between cause and effect. This type of system cannot be described on one level, or with one view. The outputs from such a system can vary - being difficult to explain or unexpected. Such complexity is often associated with the concept of unintended consequences, where unexpected properties or behaviours arise from the interactions of the parts (emergent behaviour). They can be seen as ‘open ended,’ because it can be hard to tell where the system ends, and another one begins. A big role for Systems Engineers is managing complexity and minimising unintended consequences by applying transdisciplinary SE practices.

Complicated, on the other hand, refers to things that are understood (or understandable), but difficult to analyse, learn, or explain. Complicated systems are not necessarily complex, but they can be made so when connected to other systems, due to a lack of understanding of the interfaces and the unpredictability of human behaviour.

There are two types of “complex”:

  1. Complexity - uncertain relationships between cause and effect (https://hbr.org/2007/11/a-leaders-framework-for-decision-making)
  2. Structural complexity - high numbers of diverse, interrelated elements (Haberfellner et al.. 2019, “Systems Engineering - Fundamentals and Applications”, DOI: 1007/978-3-030-13431-0.

Systems Engineers working on modern transport systems seek to manage both kinds of complexity, but the approaches are very different. Structural complexity is a calculable parameter derived from the number of parts and interrelationships between these parts. Dealing with complexity driven by uncertainty, however, often requires human solutions that do not have mathematical basis. 

The benefits

Systems Engineering is the best way we have of understanding and working with complex engineered systems. Applying SE reduces cost and schedule overruns while improving predictability. SE promotes up-front planning, engages stakeholders, and enables better documentation. It improves long-term operations, maintenance, and upgradability. It encourages disciplined verification and validation against requirements while promoting greater procurement flexibility.


The need for SE can be seen in the challenges that future transport systems are likely to face. For example, SE principles are commonly used in the automotive industry to design vehicles, but less often in the planning and delivery of the full lifecycle of roads and their associated infrastructure.

To take another example - road transport (the movement of goods, services or people using road infrastructure) is likely to become much more dependent on the future application of SE principles to the wider road transport system of systems, including the vehicles, road infrastructure and communications networks that will connect them with travellers, customers, service providers and operators. It is difficult to see how prospective developments in road transport can be delivered effectively without an SE approach that spans the related industries, services and government (and its agencies).

Making it more difficult

The aerospace sector is made up of products and infrastructure in both the civil, defence and space arenas that transport goods and passengers by flight. Distances vary between short hop commuter trips and interstellar exploration, requiring a global scale organisation to build, service and operate the fleet.

Already there is considerable complexity within the aerospace industry. Systems Engineering is pivotal in the design, monitoring and control of highly diverse supply chains. The expanding dependence on data and systems, alongside the increasing need to demonstrate safe aerospace operations, means SE will play a growing role in aerospace products and services.

The marine and rail sectors are also essential to transport. As we will see in upcoming blogposts, they fulfil roles that cannot be addressed by road and air. The marine sector is particularly suited to transport of hazardous goods, while rail is a clear winner for sustainable passenger transport in many scenarios.

Share your thoughts: 

Can the differences in the application of SE principles in Road Transport and Aerospace be associated with the different regulation of the users? Or is it just easier to maintain safe separation of entities in an Aerospace SE approach than it is for highways?

How should highway operators incorporate safety requirements into their SE approaches when they are heavily dependent on the users for safety performance?

How should highway operators cope with the scale of uncertainty in a SE approach to network management?

How can cash-strapped and sceptical politicians and program managers be persuaded to invest in SE?

Contributing Authors: Matthew Clarke, Stephen Powley, John Kelly, Iain Cunningham, Vanessa Mascall, Andy Harrison, Dr. Andrew Hussey, Gareth Topham, Dr. Raj Takhar, Dr. Michele Fiorini, Jana Skirnewskaja, Kareem Drysdale, IET Transport Panel Ecosystems Challenge Group. Partner organisation: INCOSE UK


  • In my Florida county we have every form of transportation:- local roads,  interstate highways, passenger and goods rail transport, shipping, airports (military and commercial), buses, and space flights (both manned and un-manned), balloon space transport (later this year).

    Peter Brooks

    Palm Bay FL 

  • In my Florida county we have every form of transportation:- local roads,  interstate highways, passenger and goods rail transport, shipping, airports (military and commercial), buses, and space flights (both manned and un-manned), balloon space transport (later this year).

    Peter Brooks

    Palm Bay FL 

  • Just send us money or visit Orlando and spend It

    Peter Brooks

    Palm Bay  

  • Thanks for sharing, Peter. A shame to hear that with so many transportation options, it can still be hard for locals and tourists alike to travel in the state without resorting to their cars. Especially considering the sometimes tragic consequences. I hope System of Systems Engineering finds its way to Florida transportation soon.

  • Hello Stephen;-

    How does the transport system work for Palm Bay? It does NOT work! 

    For example the high speed passenger train service does not currently stop in our county. It was designed to carry tourists from south Florida (Miami) to Central Florida (Orlando). 

    It is cheaper and gives one more travel options by traveling to Orlando airport by cab or car, instead of using our local airport. 

    The cruise ships that use our port are filled mainly with passengers that are bused or use cars, usually directly from Orlando.

    Summer time the Atlantic beaches are filled by people coming from Orlando by car.

    The good news is the biggest hospital in the area uses helicopters to pick up the dead and dying from accidents on the Interstate highway. We are effectively half way between Miami and the state line and people get into accidents when they get tired driving after a few hours. We call our section "Blood Alley".

    I interface on a regular basis, with our local County Transportation department. They have a number of road improvements in the planning phase BUT no money has been assigned by the State for these. I believe it is because of the low number of people who "permanently" live in the county year round. 

    Peter Brooks

    Palm Bay 



  • Sounds like you're very well served in Palm Bay, Peter. How well do you find that the different transport modes work together as a transport system of systems where you are?