The Naturmobil is a horse-powered vehicle for travel on paved roads. The vehicle is controlled by a driver in a similar way to a motor-driven vehicle, with the horse inside the vehicle on a treadmill. It weighs 300 kg (660 lb), or probably around 700 kg (1,500 lb) with the horse. It cruises at about 20 km/h (12 mph), with a top speed of about 80 km/h (50 mph). The treadmill also charges batteries which will power the vehicle if the horse needs a break.
The vehicle was invented by Abdolhadi Mirhejazi, an Iranian engineer, who says "the Naturemobil was developed with the safety and welfare of the animal in mind". At least one veterinarian, Dr. Matt Pietrak, has concerns for the horse's wellbeing while powering the vehicle.
The tax horsepower or taxable horsepower was an early system by which taxation rates for automobiles were reckoned in some European countries, such as Britain, Belgium, Germany, France, and Italy; some US states like Illinois charged license plate purchase and renewal fees for passenger automobiles based on taxable horsepower. The tax horsepower rating was computed not from actual engine power but by a simple mathematical formula based on cylinder dimensions. At the beginning of the twentieth century tax power was reasonably close to real power; as the internal combustion engine developed, real power became larger than nominal taxable power by a factor of ten or more.
The so-called RAC horse-power formula was concocted in 1910 by the RAC at the invitation of the British government. The British RAC horsepower rating was calculated from total piston surface area (i.e. "bore" only). To minimise tax ratings British designers developed engines of a given swept volume (capacity) with very long stroke and low piston surface area. Another effect was the multiplicity of models: Sevens, Eights, Nines, Tens, Elevens, Twelves, Fourteens, Sixteens etc. each to fit with a taxation class. Larger more lightly stressed engines may have been equally economical to run yet, in less variety, produced much more economically.
The system of imperial units or the imperial system (also known as British Imperial) is the system of units first defined in the British Weights and Measures Act of 1824, which was later refined and reduced. The system came into official use across the British Empire. By the late 20th century, most nations of the former empire had officially adopted the metric system as their main system of measurement, but some Imperial units are still used in the United Kingdom and Canada.