American Ambulance Field Service (from an ambulance specific website)

When German troops invaded France in 1914, the American colony of Paris set up a volunteer ambulance service to transport the wounded from the front lines to the American Hospital e Neuilly (outskirts of Paris). It uses Ford "T model" cars, whose reliability and ease of use are very valuable.

The volunteer ambulance train sections of twenty to thirty individuals, assigned to French combat units and sent directly to the front. At the beginning of the year 1917 there are more than two hundred cars in activity.

http://ambulances.centerblog.net/rub-histoire--5.html