1.2.1 Throughout the Guidelines the term “motorcycle” is used to cover all forms of powered two wheelers (PTW) from the smallest mopeds, through scooters to the largest sports and touring machines.

The terms “twin track vehicle” and “single track vehicle” are also used in the Guidelines. Although the terms are far from elegant, they do focus on the fundamental design differences between motorcycles and other motor vehicles that often lead to the misunderstanding at policy, design and operational levels with consequent under-performance of the road environment.