Vienna (where I live) still has many horse drawn carriages. Some years ago, the city created an ordinance that inside city limits, the horse have to have a tarp that hangs behind and below them to catch their "horse apples." The tarp is triangular and angled so that it doesn't rub the horses legs but still catches everything.

There was a huge outcry from the drivers at the time, but the city held fast and it has made a huge difference in that all the roads to/from the city center and the area near the Danube where the carriage owners traditionally live is not strewn with a trail of horse shit daily.