Complex sentence: It was frequently found that ambulances were hearses--the only available vehicle that could carry a recumbent patient--and were thus frequently run by funeral homes, these vehicles which could serve for either purpose were known as combination cars.
Split into simpler sentences: It was frequently found that ambulances were hearses--the only available vehicle that could carry a recumbent patient--and were thus frequently run by funeral homes. These vehicles which could serve for either purpose were known as combination cars.