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Induced Traffic

Planners say things like this: "If you build more roads, you will get more cars".  This is not an expression of personal cynicism; induced traffic is a real thing and it has been studied extensively. The new road, which will provide a sort of worm-hole between the high traffic arterials of Minton and US192, would seem to be ripe for inducing new traffic.

Here’s a brief description of how induced traffic works, taken from a recent study:

 

"Traffic engineers often compare traffic to a fluid, assuming that a certain volume must flow through the road system, but it is more appropriate to compare urban traffic to a gas that expands to fill available space (Jacobsen 1997). Traffic congestion tends to maintain equilibrium: traffic volumes increase to the point that congestion delays discourage additional peak-period vehicle trips. Expanding congested roads attracts latent demand, trips from other routes, times and modes, and encourages longer and more frequent travel. This is called generated traffic, referring to additional peak-period vehicle traffic on a particular road. This consists in part of induced travel, which refers to absolute increases in vehicle miles travel (VMT) compared with what would otherwise occur (Hills 1996; Schneider 2018)."

 

You can read the whole study here:

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It has been known since the early years that the Doherty Drive Ext will generate induced traffic. For example, the Neel Schaffer engineers stated as early as 2011 that: "Based on local knowledge of the traffic patterns, the extension of Doherty Drive will attract regional traffic to this new roadway connection."

(See highlighted text in PDF below.)

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