How does some cars know when a road narrows?

[roadman65]

I rented a Kia Seoul which displays a Yield icon on the dash when I enter a merge or lane drop.

Plus it displays a tiny speed limit sign at speed limit changes and even knows when a curve is approaching and displays a curve warning sign with the direction of the curve.

It can't be radar as you would need a fixed object to fixate on. So I'm guessing it has a camera with certain signs programmed into the computer that is activated when certain signs are caught by the camera and makes a match.

[jakeroot]

Road (traffic) sign recognition is a very common feature:

https://en.wikipedia.org/wiki/Traffic-sign_recognition

My friend's Suzuki Hustler makes a double beep noise anytime we approach a stop sign, displaying the stop sign on the dashboard.

For the record, the *Soul is not named after the South Korean city. Although admittedly, "Seoul" would be quite clever.

[bwana39]

My Fords have recognized the striping on the road.

[Henry]

I think cars and trucks equipped with hands-free driving (such as the various GM vehicles from the Sierra to the new Caddies) will also detect the changing road conditions and react accordingly.