The RSPCA is now appealing for the public's help in tracing those believed to be the animal's owners, after they left the injured horse at the scene.
The charity has issued photographs of two men it wants to speak to about the incident which happened in Great Bridge Road, Bilston, West Midlands, on Sunday afternoon.
The horse had been pulling a trap and was part of a procession of other carriages, when the incident happened. Members of the public were left to help the animal, which was "bleeding profusely" from wounds to her front and legs, animal welfare officers said.
"The horse was lying in the road and bleeding where the smashed windscreen had cut into her front and legs. This was a shocking sight and she was clearly suffering." RSPCA inspector Vicki Taylor
The car which the horse collided with was left badly damaged - but the occupants escaped unscathed (RSPCA/PA)
The inspector added that although the incident must have been "a shock", she claimed the men had "abandoned" the horse to its fate by leaving the scene.
The horse, which escaped without broken bones, is now at boarding stables and should make a full recovery, according to vets.
Anyone who recognises the horse, or the men in the picture are being urged to contact the RSPCA by calling 0300 123 8018.