OP's query is on an excerpt from the novel Fat City by Leonard Gardner.
What is the meaning of "remained in high cones"?
Far ahead points of light appeared and drew closer, shifted down to
the road or remained in high cones, glaring in the eyes of the three squinting out the windshield, the dimmer clicking on the floor, the woman behind the wheel saying: “Son-of-a-bitch."
We have to consider that this novel was written in 1969 and the story is set in Stockton, California.
My understanding is based on the excerpt OP provided, as I couldn't find anything on the setting.
Here's phrase by phrase explanation:
1. "Far ahead, points of light appeared and drew closer":.
- Points of light refers to the headlights of an approaching vehicle. (They saw a vehicle/ car coming from far and it came closer to them)
2. "shifted down to the road or remained in high cones":
- The oncoming driver put the headlight in high beam. High cones refers to the shape of the high beam.
- but sometimes he would shift to low beam.
3. "glaring in the eyes of the three squinting out the windshield":.
- As the oncoming car was in high beam, it hurt the eyes of the three occupants of the woman driver's car, making them squint. (squint = to look at something with your eyes almost closed)
4. "the dimmer clicking on the floor":
- It's possible that the dimmer switch was operated by the foot. The woman driver operated the dimmer switch (clicking means switching on and off hence flashing her headlights). This was done to alert the other driver.
5. "the woman behind the wheel saying: 'Son-of-a-bitch'":.
- She showed her annoyance at the other driver's high beams.
"Driving with high beams towards oncoming traffic is prohibited, as it can blind other drivers."