A recent suggestion (Nov. 2) by one reader held Caltrans responsible for flow problems on local freeways. Like most blaming, especially political blame rants, it was a poorly informed emotional outburst, rather than a reasoned consideration.
One of the basic courses required of all engineers and physicists is a course that instructs about fluid dynamics. In this course engineers (and physicists, and anyone else interested, I suppose) learn about two types of flow: compressible and incompressible.
Compressible flow means that the medium, like air, will squish by a large amount because its molecules are spaced loosely. Incompressible flow means that the molecules are already packed pretty tightly, and may yield space between the molecules only by a small amount, until the bulk substance reaches “absolute zero” when its molecules are — hypothetically — completely de-energized, “frozen,” in time and space.
As a common example, in our earthbound environment air experiences compressible flow until it becomes liquid, then it is incompressible. This is precisely how air is liquefied: It is passed through a small orifice at high pressure and yields all its energy as heat.
Thereafter, liquid air pushes back substantially upon lower pressure environments where its molecules can be freed from its low-energy binding. It must be contained in fortified pressure vessels to protect the compressed substance from escaping.
Traffic is incompressible flow. Cars cannot grow smaller or the spacing between them shrink to infinitesimal size when passing through a junction or other choke point in the network, AKA “roadways.” Thus, just like in any network, the smallest orifice in that network will always be the unavoidable choke when surging pressures from increased volumes of traffic demand passage.
Design out that choke point, and the next one becomes evident once surging volumes again demand passage.
This is a simple fact of physics. Ask any engineer or physicist. Until we learn to bend spacetime, we will suffer these limitations of matter.
Christopher Lucero
Saugus
