In the late 19th century, the innovation around internal combustion engines and fuel injection technologies began. The technology proved the existence of a viable solution that could be applied to a number of fields. Transport was one of them. The inventors/innovators were tinkering with the engines, trying to find the most compact, lightweight, and efficient system. The viability of engine technology opened up possibilities of replacing horse-driven carriages with human-controlled automobiles. The earliest version of a finished, usable automobile was an engine fitted onto a two-wheeled (cycle-like) frame. This was called the riding car (see the following image):
An article about the car says, "The most important prerequisite for the riding car, simultaneously the world's first motorcycle...