Lots of people who wear transitions lenses also have a pair of prescription sunglasses. Often the sunglasses would be just single vision distance lenses, so they can be worn for driving.
The reason for this is that transition lenses are not as effective when being worn in a car. The transition lenses react to the UV rays in the sun, so are excellent for walking outside, or reading in sunlight etc.
However the car windscreen has a UV filter, which stops a lot of the UV rays from going through the windscreen. hence, the transition lenses don’t go as dark as they would if you were outside of the car. This is where a pair of prescription sunglasses is very useful as they stay dark the whole time.
The dark shade of sunglasses is often darker than transition lenses at their darkest as well, making them more effective when the sun is set particularly low in the sky. The winter sun is set lower on the horizon, making it dangerous as the glare can be dazzling for the driver at times. Dark sunglasses are far more effective than transition lenses on these occasions, and highly recommended.