On smooth road one horse can pull 10 members easily. It can speed 50 km per hour @5 people load.
Whether my calculation will be right or wrong but where the efficiency is getting wasted.
1HP for 5 people. 1000 HP engine is doing what.. hardly it is pulling 1000 peoples max @ < 50 km avg speed.
One more thing is hourses...
more... are inteligent than engine, doesn't required any red and greean with intermediate orange signaling system.
I hope horse can be ride in fog atmosphere also.
Future fuel may be grass only.