No vehicle on earth is entirely free of emissions; even electric cars charged on renewable energy have emissions associated with their manufacturing.
Those emissions, however, are a tiny fraction of the carbon dioxide and other substances emitted by gasoline or diesel cars when scientifically assessed on a "wells to wheels" basis.
This is well established, but it has only reached government policy makers in a handful of places, including Norway.
DON'T MISS: Norway's Goal: All New Cars Will Be Emission-Free By 2025 To Cut Carbon
That country plans to phase out sales of new vehicles with combustion engines entirely by 2025, as part of its multipronged efforts to cut the country's carbon emissions radically.
And the inspiration of Norway made us wonder whether there might be a parallel to smoking in the persistence of vehicles that emit harmful substances into our shared air.
Twenty years ago, smoking in offices, shops, restaurants, and other public places was common.
When will it be unacceptable to drive a car with a tailpipe?— Green Car Reports (@GreenCarReports) March 27, 2017
Today, it's banned, largely for public health reasons: the smoker has a right to hurt his or her lungs, but the rest of us shouldn't have to be hurt in the process.
So we asked our Twitter followers when, if ever, they thought it would be seen as unacceptable to drive a car with a tailpipe.
CONSIDER THIS: When Will We Start To See 'Tailpipes' On Cars As Morally Wrong? (Nov 2015)
Only 18 percent said that would "never" happen.
Responses to the other three options resembled a rough Bell Curve, with more than one-third of respondents (37 percent) picking "by 2035," the middle option.
Electric cars parked on the streets of Oslo, Norway [photo: Wikimedia Comons]
One quarter (27 percent) picked "by 2025," the most optimistic of the three years cited.
And 19 percent said it would happen only "by 2050."
Today, the planet has roughly 1.2 billion vehicles on its surface, with fewer than 1 million of them zero-emission (whether battery-electric or the much smaller number of hydrogen fuel-cell) vehicles.
With lithium-ion battery costs falling at an average of 7 percent a year, perhaps more, the point at which plug-in electric cars with 200 miles of range will be affordable to the mass market is starting to come into sight.
CHECK OUT: Trump's climate-change order: now what happens?
Once that happens, how long do you think it will take before driving a car that spews greenhouse gases and other toxic substances into the air will be viewed in the same way as lighting up a cigarette in an airplane?
Green Car Reports respectfully reminds its readers that the scientific validity of climate change is not a topic for debate in our comments. We ask that any comments that deny the accepted scientific consensus on climate change be flagged for moderation. Thank you in advance for helping us keep our comments on topic, civil, respectful, family-friendly, and fact-based.