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PaperclipPerfector  5mo ago (text post)   4774 thread views

Small-Scale Question Sunday for July 7, 2024

Do you have a dumb question that you're kind of embarrassed to ask in the main thread? Is there something you're just not sure about?

This is your opportunity to ask questions. No question too simple or too silly.

Culture war topics are accepted, and proposals for a better intro post are appreciated.

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Adding wide, convex rear-view mirrors (both interior and exterior) to your car makes changing lanes on the highway absolutely stress-free. This image is only slightly exaggerated: with a wide, convex interior rear-view mirror, you can watch through the rear window and through the right rear passenger window simultaneously (especially after removing the headrest from the front passenger seat).

Why is this not standard on every car? It seems so obviously superior.

Under the relevant section of the Federal Motor Vehicle Safety Standards (a set of regulations issued by the National Highway Transportation Safety Administration), only the passenger-side rear-view mirror is permitted to be convex. (That's the reason for the "objects in mirror are closer than they appear" warning.) The interior and driver-side mirrors, on the other hand, are specifically required to be flat ("of unit magnification").

Some cursory searches (1 2) of the Federal Register do not reveal any discussion of the rationale behind this particular rule. However, one other discussion appears to be related. On vehicles that are heavier than five tons, the passenger-side rear-view mirror cannot be convex, but is required to be flat like the other two mirrors. Way back in year 2000, AM General, the manufacturer of the Hummer H1 (with gross weight of 5.15–6.05 tons), requested that this rule be changed to match the rule for passenger vehicles. With typical government alacrity, NHTSA took five years to reject the request:

Despite public commenters' expressions of support for a convex-mirror option for the vehicles in question, the agency remains concerned about the difficulties that drivers may encounter in correctly judging distance and speed of approaching traffic if the vehicle is only equipped with a convex mirror. As stated in the Request for Comments, although convex mirrors are permitted on the passenger side of light vehicles, the agency still receives complaints from consumers about these mirrors. "There have been other problems associated with the use of convex mirrors that include double vision, eyestrain, and nausea."

Thanks for the effortful reply.

Seems like it's a hodgepodge of regulatory fuckery and legitimate but probably outlier issues with vision, distance judging, etc.

I await the day where full self-driving car manufacturers have to confront regulatory bureaucrats who ask questions like, "Can the AI use flat mirrors during lane changes, or would it prefer convex ones?"

especially after removing the headrest from the front passenger seat

Surely the passenger would object?

In approximately 98 percent of my trips, there is no passenger. I keep the front passenger seat's headrest in the rear seats' footwell, so that, in the rare event that I do have a passenger, the headrest can be reinstalled in just a few seconds of toolless effort. Your situation, and your vehicle, may be different.

As an alternative to removing the headrest, you can just fold the seat back so that the headrest doesn't block your view.

Huh. That's pretty neat.

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