Michael J. Smith lives in Portland, having recently relocated from New York City.

A recent article about some murky doings at the Portland Police Department (“Longtime Portland police leader says he was fired,” Oct. 24) reminded me of one of the reasons why I think engineering is better than enforcement.

Let me tell you a story. My own old car doesn’t have all the contemporary mod-cons. But I recently rented a newer one, which had a thing called “adaptive cruise control.” All of y’all probably know what this is, but I didn’t. It slowed us down — the car and me, I mean — if we got too close to what I’ll call the “drivercar” (a symbiotic organism, like a lichen) in front of us.

And then it would come back up to the preset speed when space opened up. All I had to do was steer — and the car helped me with that, too. Knew where the lane stripes were. Very intelligent, this car. Almost as smart as a dog, though with less personality. Smarter than many drivers, in fact, and morally superior. Never got annoyed, never got competitive.

The car also displayed my whereabouts on the dash, and — this is where it gets interesting — showed me the local speed limit. So the car knows what the local speed limit is. And of course it knows how fast it’s going.

Naturally, it occurred to me that the only thing missing here is a widget — call it, in my honor, the Smithwidget — in between accelerator and throttle that would take the local speed limit and the car’s actual speed as inputs, and not allow the car to go any faster than the limit. (For newer cars, the Smithwidget is just a software modification.)

And presto, all those cops sitting by the road, supposedly enforcing the speed limit, and doing a very poor job of it, become redundant. They have, in effect, been engineered out of the speed enforcement business.

Of course, sometimes engineering needs to be backed up by enforcement. Suppose, for example, that some fiendishly clever driver finds a way to disable the Smithwidget. Clearly this fiend needs to be caught and punished. But once the Smithwidget becomes ubiquitous, the only speeders will also be widget-disablers. And much of enforcement can be engineered too, with license cams, for example.

Street design is the locus classicus for engineering over enforcement. In a compact urban setting like Portland, for example, it should be physically impossible for a drivercar to make a fast wide turn through an intersection. He/it should be required to make a slow, sharp, 90-degree turn.

This is just a matter of street geometry, and it works passively, tirelessly, ineluctably, impartially, year-round, night and day, rain and shine. It needs little if any maintenance.

It doesn’t require electricity, or any human effort, except the initial redrawing of the curb line, and the installation of some serious bollards, bollards that mean business: thick cast-iron bad bois, painted poison-green, whispering “body shop” in the driver’s ear. Perhaps with a lamppost on top, human-scaled rather than car-scaled — a lamppost that whispers “walker country here.”

For the same reason, roundabouts are better than stoplights and stop signs. I dream of State and High, here in Portland, being two-way again, and most of the lights replaced with roundabouts. And the notoriously awful Woodfords Corner absolutely cries out for the roundabout treatment.

Enforcement, by contrast, depends on cops, who are expensive and don’t do a very good job of it — being subject, unlike bollards, to various human frailties. Enforcement is erratic, arbitrary and selective — we all know what I mean here — and leads to interactions between cops and the public, which all too often end badly.

And cops themselves tend to suffer from car brain (more politely, windshield perspective) and over-identify with the driver. So hey, let’s give a lot of cops early retirement and a nice pension and make some modest changes to our streets.

And, bring on the Smithwidget!