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Why are there so many "Push to Cross" buttons at intersections in Portland, instead of having the signal automatically change to "Walk"? It is extremely frustrating and dangerous.
—T. Walk
At the risk of offending you, T. (a risk I'm always happy to take), I feel we should first explain why this is not a stupid question.
Since it's well known that traffic signals are pan-galactically coordinated, citywide, into a precision-timed matrix of efficiency, doesn't it screw up the whole system to let T. introduce an extra 30 seconds of ped-crossing time into the equation every time he wants to shuffle his shopping cart from hither to yon?
Indeed it would—in some naive fantasy world where the signals do what we tell them to do, when we tell them to do it. Poor, simple human! Your button-poking is merely a data point in the traffic-control system's cosmic calculation.
Pressing the button is analogous to a car driving over the sensor in the pavement—it tells the system that somebody is there, wanting to get through. Then it's up to the computer to decide, based on overall traffic efficiency, when and for how long to let everyone pass.
When there's no tedious human waiting to cross, the system can squeeze a few extra cars through every cycle—worth the effort on some high-volume arterials where foot traffic is inconsistent. (You'll notice they don't bother with the buttons downtown.)
All of this is done in the interest of making sure that even the spaciest, least attentive of your fellow citizens (i.e., yours truly) can cross the street without getting flattened. It may be frustrating, T., but unless you find waiting for the signal so vexing that you blow your brains out in a fit of pique, it's not dangerous.
WWeek 2015