How did the best engineers come up with their ideas? What can we learn from the engineer who built the world’s tallest building or the first highway engineer? These are the questions biomedical engineer Guru Madhavan addresses in his new book, Applied Minds: How Engineers Think, recently published by W.W. Norton & Company. In this adapted excerpt, Dr. Madhavan brings those problem solving skills to life by telling us the of some of the best engineers in history and giving us a peek into how we can apply those problem solving principles to our own projects.

John Shepherd-Barron was an old-fashioned Scotsman with a questioning mind. One afternoon in the mid-1960s—as the story goes—Shepherd-Barron was a few minutes late to the bank as it was closing for the weekend. He urgently needed cash. The manager refused to reopen the branch, despite his pleas. A dyed-in-the-wool engineer, Shepherd-Barron thought he should have the freedom to withdraw cash anywhere and anytime from his bank account. He was the managing director of a currency instruments firm. He worked first on the printing side of the business, and then on the armored transportation side. His next step was to find a way to dispense money automatically. By inventing the automated teller machine (ATM), he completed the circle. How did he do it? “I hit upon the idea of a chocolate bar dispenser, but replacing chocolate with cash,” said Shepherd-Barron.

The idea of a tremendous engineering achievement like the ATM may seem to have arrived out of thin air, but perhaps not. Having your mind prepared to exploit an opportunity is an important precursor to spotting one. The engineering frame of mind is systematic and especially adaptive toward producing useful and practical solutions. Contrary to the popular perception, engineering is much more than creating gadgets and codes. It is a foundation for life and cultures rooted in curiosity, practicality, and iterative improvement. Tools and concepts of engineering can help boost the dexterity of our decisions and efficiency of our solutions in business and life.

Backward Thinking

The engineering mind-set sees structure where there’s none, is adept at producing utility under constraints, and making considered trade-offs in the scheme of what’s available, what’s possible, what’s desirable, and what the limits are. Additionally, what’s even more handy for engineers like Shepherd-Barron is the powerful concept of backward design: the ability to pre-imagine the desired outcome and work in reverse to achieve that goal. An epiphany, then, actually results from conscious, methodical planning that supports a confluence of ideas, experiences, and opportunities. Lehigh University’s Tom Peters has used the term matrix thinking—comparable to the moving around of ideas across the rows, columns, and diagonals of a conceptual matrix—to define an orderly process of spotting, incubating, and combining ideas from various walks of life, and then converting them into practical solutions. Applying this sort of logic to the development of the ATM, we could say that goal-oriented thinking helped shape a highly focused function: a reliable way of dispensing cash. In imagining and parsing the system and modules of the ATM, from security to data storage, Shepherd-Barron could have worked entirely backward to form a framework for what we now call telematics—a system of systems that unites computing, telecommunication, and transportation technologies.


The operating principles of ATMs—let alone automobiles and airplanes—are based on reliability. ATM failure rates have significantly declined over the past several years, thanks to concurrent error detection algorithms in the software that processes transactions, and to redundancies in the ATM network. The security features of ATMs have improved enormously. Our transactions are secure and ultrafast, even if an ATM has to query a group of connected systems that may not be anywhere near the machine we’re using. Whether it’s a theme park ride or a bank account, the general principles of safety are the same. As a design requirement, engineers always need to take extra precautions, include failsafe options, factor in backups, and establish redundancies. Indeed, as one joke goes, that’s probably why engineers wear both belts and suspenders. By iteratively refining the technologies over many generations, engineers are able to produce systems that offer reliable solutions and standards. As examples, let’s consider three more creations.


In the late 1860s, John Peake Knight designed and installed a revolving gas-powered lantern—with red and green light—operated by a police officer at an intersection near London’s Westminster Bridge. This arrangement was to streamline the traffic jams caused by carriages and people. It offered people not only a technical logic but also a visual logic for order at an intersection. Knight adapted this traffic light idea from his previous experiences working as an engineer for the British railways. He used the semaphore train signaling system—whose arms moved horizontally and vertically—as a template. Knight’s innovation was in creatively revising an existing setup and establishing a flexible standard for future engineers. Several decades later, a police officer adjusted Knight’s idea for a synchronized four-way, three-light system. This addition not only helped people who were color-blind, but also eliminated abrupt changes by adding more control in the traffic management process. As an example of an even more recent tweak, consider the addition of cameras to the traffic lights. Just imagine how many lives a red light can save at four-way intersections around the world.

Aesthetics and Function

Now let’s explore the work of Edward Hines. He was a self-invented highway engineer by “inspiration and choice,” and loved to cycle “until his muscles went on a strike and his vertebrae demanded shock absorbers.” His grand ideas to improve Michigan Wayne County’s infrastructure led him to construct the world’s first concrete road in 1909. It was one mile long. In 1911, he wanted to improve road safety after he spotted a motor car and a buggy coming from opposite directions collide. One evening while riding on his bike Hines followed a van that started leaking milk. The outflow created two lanes. And that’s how the idea of a “silver lining” for the road—or center line safety stripe as Hines called it—was born. It was a bingo moment—similar to how Shepherd-Barron hit upon the ATM idea—that rapidly influenced the design of safer highway systems around the world. The concept of traffic lanes—coupled with speed limit in later years—led to what we observe as lane discipline. This approach not only created a new standard of operation but also convenience for slower vehicles to stay on the right. Highway snow removal became efficient. Mid-road beautification became possible. The idea for this simple lane was a perfect blend of artistry and durability.

Setting Standards

Now onward to an even older technology. In downtown Washington, DC where I live, hardly an hour passes by without the “sonic hysteria”—an anthem to presidential security or for the ambulance wriggling through the traffic. Sirens are part of our sociocultural soundscape. They have a singular ability to garner attention and deference. In 1819, a French polymath engineer Charles Cagniard de la Tour significantly improved an older version of a “noise making device” that got him interested in the science of sound. The inspiration for acoustic sirens appears to be from the different sounds emerging from the plucking of the violin. These sirens were originally designed to be used as a musical instrument but a mere manipulation of their output into a binary “hi-lo” pattern resulted in an entirely different application. Cagniard’s simple modification to the instrumentation—a pneumatic device with two dials—enabled the siren to be operated at different pitches and also under water. Subsequent applications during the war times helped elevate sirens to a distinct place in our society. From births to deaths, they continue to serve as a standard in our perception of emergency.

Continuous Refinements

Technologic systems like ATMs, traffic lights, highways, and sirens have a common feature. They were all designed iteratively despite (and often because of) constraints—namely, the physical laws of nature, cost, time, resources, performance expectations, and also human behavior. The inspiration for the structured thinking emerged from different settings, namely a chocolate vending machine, the train signal, a leaky milk van, and a music instrument. In this evolutionary narrative, each of these technologies at one point was sub-optimal but successively improved upon and trade-offs routinely assessed.
Similarly, we humans are also evolving prototypes, and Mother Nature is the ultimate prototype of prototypes. However, the evolutionary processes of nature aren’t goal oriented whereas the value of engineering is determined by its outcomes. The creations of engineering offer utility and value far more than other professions. There’s hardly a scenario where the engineering mind-set doesn’t add value or fresh new perspectives, and there are vital benefits to be gained through this mode of thinking.

About The Author

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Senior Program Officer and Project Leader at the National Academy of Sciences

Guru Madhavan is a biomedical engineer and senior policy adviser. He is author of Applied Minds: How Engineers Think.