I ride a performance enhanced 1200cc Harley-Davidson Sportster.
In my past,I rode high performance offroad racing motorcycles that were over 400cc.
The absolute most dangerous machine I ever saddled up was a 350cc motorized offroad trike with a solid rear axle
As a rider of two wheeled motorcycles offroad,placing one boot on the ground was a part of cornering in bad conditions. The end result of attempting that on my trike was it running up the back of my leg as it ripped me past the handlebars before it finished running over me. The sale of new offroad motorized trikes was made unlawful in the USA over the damages,injuries and deaths resulting from them.
Street trikes are not illegal,but are quite dangerous just the same.
The latest street trike configuration of having two wheel in the front with one in the rear are considered safer because the front end will have less tendency to wash out resulting in loss of control.
Most motorcycle accidents are a result of failing to negotiate a turn as a result of steering traction loss
Being a motorsports enthusiast,I can tell you that any motor vehicle with three or less wheels is considered a motorcycle,adding a fourth wheel makes it a car
A pedal powered 4 wheel machine is considered a quadricycle,but the additional rolling resistance of the fourth wheel makes them impractical, heavy and not well suited to rough terrain due to lack of suspension.