Letters & Opinion

Engineering Common Sense

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By John Peters

I have always said that good engineers must have common sense, and it is important for any young engineer to understand the fundamental principles of engineering. At times I see activities that challenge my hope for the future of the profession. There are simple things like how to fix a pothole so that it can last, the basics of cutting and squaring the pothole and compacting the pavement layers. I have seen recent activity where the asphalt is virtually dumped in the hole and left to be compacted by traffic, that certainly is not common sense.

I went to Vieux Fort and observed the repair to the failed culvert at Micoud, and again wondered where common sense left the design. You cannot expect an embankment to be stable with that angle, and the next major storm event will see the section of fill just above the culvert erode and the entire embankment fail. So an understanding of the fundamentals of engineering is important.

When we are dealing with materials there is some consistency in their behaviour, and thus scientists can predict the behaviour of a mixture of aggregates, cement and water which we call concrete. They can predict the properties of reinforcement steel, and thus generate design parameters for the construction of a building.

Common sense is seen as the way we should view engineering issues. However, when we introduce the human element, the predictability fades. Transportation engineering involves the human element and thus there are transportation matters that do not make sense. How many times have you been stuck in traffic on the Gros Islet Highway and believed that it was an accident that caused the traffic jam, only to continue and realize that there was no reason for the delay.

Scientists have now started to look at traffic as a chaotic problem, that can be explained by chaos theory, a concept which I will explain later. We think that traffic is a linear problem, and so if there is traffic problem on the Gros Islet Highway, the first thing that comes to mind is to increase the number of lanes. However, every day we see this thinking fail. If traffic was a linear problem, then if one lane on a dual carriageway is closed then the travel time should double. So for example if there is an accident on the section of the Gros Islet Highway from Choc to Vigie and the police shuts down one lane, then if it took you ten minutes before, it should now take you twenty minutes for the journey. We all know that is not the case, so why do we accept the reverse, that increasing lanes will shorten travel time.

Chaos Theory in a very simplistic manner is saying that a small change causes a dramatic effect. The human nature can cause a chaotic problem. If there is an accident on the road and the police have cleared the vehicles off the road so that there is no blockage, there will still be a significant traffic jam. This is because every driver slows down to look at the accident and that small effect on the flow of the traffic when the driver slows down causes a dramatic effect miles behind. In the Caribbean, it is even worse as the drivers come to a complete stop to see the number plate, ask a question, take a photo and every imaginable thing. Those way back remain confused when they reach the accident and the road is completely clear. Chaos theory is at work every single day on the Gros Islet Highway.

Solving traffic problems is not based in part on what may appear to be common sense, largely because of the human element. Transportation engineers in the past have viewed traffic problems in a linear manner and on similar concepts to hydraulic flow. The more capacity will give the greater flow. Therefore to solve the traffic problem on the Gros Islet Highway, we will increase the number of lanes. This day, I lay down a challenge to any transportation engineer to produce any evidence that increasing the number of lanes from Choc to Rodney Bay will reduce travel time into Castries.

The present thinking is to view traffic as a solitary travelling wave, a chaotic problem and a network problem. If it is a solitary travelling wave then any slow down of the wave on the Sans Souci bridge will have a net effect way up the road. In essence if you have a slow entry into Castries, it creates a magnified effect further up the road, thus affecting travel time. If it is a network problem then a possible solution is to improve the options of travel and expand the network.

I firmly believe that the first priority should be to expand the network of what we call the ‘back roads’. I would strongly urge the government to follow through with this component of the project and expand the network of roads off the Gros Islet Highway. When this is completed an assessment should be done before the next phase of building a four lane highway; this may be the common sense component.


  1. Eng. Peters, you can not in good faith call that fiasco on the Micoud culvert a design. It burns my eye looking at that embarkment and knowing full well: Its a Register Engineer performing that nastiness, it hurts even more that you did not elaborate more that fiasco. Keep giving ’em hell.

  2. Eng. Peters, I do agree with you. Traffic jam is a condition on road networks, as the road capacity is maximized, extreme traffic congestion sets in. Though you failed to correctly diagnose the heart of the congestions at rush hour, namely: What slows the speed of the traffic stream? Notice as demand approaches the capacity of the intersections along the road, extreme traffic congestion sets in as well. Modern roundabouts replaces out dated intersections, We also have a Network Overload, these are the bottlenecks and traffic snarls where demand always outweighs capacity. So yes, its time “to improve the options of travel and expand the networks”. And the ever growing problem of pedestrians crossing the main roads.

  3. Eng. Peters, your opinion page stayed clear from The Intersection chaos for good reason: you can not advocate back roads expansions and hold back road capacity building. No, the two goes hand in glove As you in improve the ease of back road movement, you also increase the volume of traffic on the main roads. Do you believe the bearing capacity of the current drive way, the thing “we call JC high way”; can handle the increase volume? So while the feeder roads are at optimal, let common sense and the politicians decide on the next phase. That science lack common sense…..

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