Two horses died when they were hit by a vehicle on the M1 on Saturday.
Six horses got out of a nearby field and on to the motorway's southbound carriageway near Horbury, West Yorkshire.
Police were called to the scene at 5.38am after the Vauxhall Corsa hit two of the animals.
One horse died at the scene while another was seriously injured and had to be put down by an armed officer.
The car driver was uninjured in the accident, while the remaining horses were safely returned to their field.
A West Yorkshire Police spokesman said: "The motorway was closed for a short period while the dead horse was removed from the scene but a local diversion between the two slip roads was put in place to keep disruption to a minimum."