Icy conditions caused at least six crashes on one of the main routes into Cardiff from Vale of Glamorgan on Tuesday morning.
Police said the collisions happened on sections of the A48, the A4226 Five Mile Lane, and the B4270 in Llandow.
In one incident, a motorcyclist was injured after losing control of his bike near the Pentre Meyrick junction.
The A48 between Cowbridge and Culverhouse Cross has since been gritted.
Gary Smart, policing inspector for Penarth and Vale of Glamorgan, said: "Conditions on many of the roads in the Vale of Glamorgan were treacherous this morning.
"Black ice is very difficult to see until it is often too late and we encourage motorists to take extra care, slow down and allow extra time for their journeys."
Vale of Glamorgan council said the route was regularly gritted but the intensity of showers had been more than that forecast.