All vehicles except maybe buses have raked (angled) windshields. That have it for aerodynamic reasons and the amounts will vary from car to car. Sports car have extreme raking, for example. But they all have it. Even most buses have some rake.
Because of the raking, they won’t reflect any light from the dome light back to the driver. All the light will be reflected downward. The reflected light you get (and it will be a lot) will be from the rear view mirror. Go ahead and try it. At night turn on the dome light and tilt the mirror away so you don’t get light from that. Now look out the windshield and see how much glare you get.
Above I dismissed the loss of night vision. I was perhaps a bit too quick on that. It’s true that other headlights and various other lights do ruin your night vision. But having a bright light shining in the rear view mirror will likely cause your pupils to contract even more than usual for night driving. So it will make your vision that much less effective. If you have to have the dome light on, tilt the mirror away and use only the external mirror. (You’ll get the same effect if you drive a sedan and a large truck (which have headlights mounted at just the right height to shine in your rear window) comes up behind you. Actually, that’s worse, because they are also shining in the external mirror.)
Back when I was driving an older car, whenever I was driving at night I would tilt the rear view mirror up a bit so that I was getting a view of the ceiling near the back of my car. Lights from behind were still visible as a reflection(?) at that angle, just not so brightly. Even non-blinding lights were still visible. Was able to avoid a lot of blinding by those big trucks that drove behind me.
I’m now driving a car with an automatic dimmer in the rear view mirror, so I don’t do this anymore. But I continue to wonder how the lights from behind were being reflected such that I was able to see them at that mirror angle.
The mirror has two viewing angles, one for day and one for night. That’s what the little lever type thing is for on the bottom of the mirror, to switch back and forth. Today some mirrors have the same function by pressing a switch/button, like your’s.
In the old days it was called a “dome light” and they were incandescent lamps behind a diffuser in the cabin roof. Today (even on less expensive cars) they are often projector lamps, sometimes individual per seat. They project a soft spot on the individual seating position. A single generic concept of “dome light” is no longer valid, nor are the hypothetical rules and reasonings about legality or safety – many cars no longer have dome lights.
There was no lever (or button) on the rear-view mirror of my prior car.
The rear view mirror in both my past and current cars had/have more than two viewing angles (more like a spectrum of viewing angles) which comes in handy when other people drive my car and have to adjust the mirror to match their view due to the difference in our heights when sitting (I’m short). Are you only able to tilt your rear view mirror at just two set angles? Really?
Massachusetts has a law concerning ‘unnecessary auxiliary lighting’. Its the law they use to ban ‘ground effect lighting’ and to ticket people for using fog lights and non oem lights(light bars, spot lights) when they are deemed unnecessary. I suppose they could ticket someone for a dome light but I don’t know of any instances of it.
I have to disagree.
My truck has no rear view mirror, just the outside mirrors.
It may have had one once, but it has apparently gone on a separate journey some 50 years ago.
Anyways, with the dome light on, it is hard to see out the windshield, because there is
a reflection of the inside of the truck, the reflection is faint kind of fuzzy, but it is there
and it is brighter than what is outside.
On night vision
Yes oncoming lights are no help, especially when aimed improperly, but they tend to pass and then they are gone, the dome light is a constant, until you turn it off.
Also, not all cars are equal in “dome lights”
Not all are in the “dome” so to speak.
My truck, it is above the rear window and faces forward.
Some cars they are dead center in the roof.
Other cars they are in or near the rear view mirror, in front of the drivers eyes
Other cars, my MGB comes to mine, the dome light is in the center console below the radio.
My challenger has a roof dome light, not helpful when driving at night at all, it’s right in the rearview mirror and poof windshield looks black and has a distinct reflection to the stupid speaker grill and defroster vents, no night vision and annoying reflection
But it has 2 below dash level “Map” lights, that are useful because they shine on the floor and dont blind the driver.
Looking down at the floor to read a map, while driving though, no so useful.
