Does the light from an oncoming vehicle's headlights cause your pupils to become larger?

Does the light from an oncoming vehicle's headlights cause your pupils to become larger?
No, they become smaller (constrict).
The pupils become larger (dilate) to let in more light. The bright headlights would cause the eyes to let in less light, which means you will not be able to see anything clearly except those bright lights. You are "blinded" until your eyes adjust again, and by that time you may have veered off the road or had a collision.