Made popular by the chopper motorcycle movement, side-mounted number plates have evolved as an alternative method of displaying legal plates without inhibiting the rear view of the motorcycle itself. However, as growing numbers of custom motorcycles hit the streets, side-mounted plates are often difficult to read, forcing the creation of new laws.
Side-mounted number plates are often mounted on the right side of the motorcycle, attached to either the rear axle block or suspension. There are two basic variations of the side-mount plate, placing the number plate in either a horizontal or a vertical position. Pricier models include integrated LED lights to illuminate the number plate, although more inexpensive mounts do not offer any type of lighting. Side mount plates are typically found on custom choppers and sport bikes. However, some manufacturers have been incorporating side-mounts in recent models. Harley-Davidson, for example, offers its Nightster model with a horizontal shock-mounted number plate.
Effects of Side-Mounted Plates
As most side-mount plates are mounted to the right of the motorcycle, viewing of the plate from the left side of the motorcycle is restricted. This has drawn some concerns by law enforcement regarding the difficulty in distinguishing number plate numbers. This concern is amplified by vertical mounted plates, which places the number plate at a right angle to the road and add to the difficulty in reading the plate. To further prevent identification, the lack of illumination on many inexpensive or home-made plate mounts makes it nearly impossible to read plate numbers at night or in lowlight situations.
State Vehicle Codes
Many states have restricted the use of vertical side-mount plates in their local vehicle codes. For example, California Vehicle Code, Section 5201, states that all rear-mounted number plates must be securely fastened and must be mounted in a position that is unobstructed, clearly visible and legible. The state of Maryland further defines that all number plates must be mounted in a horizontal position, as stated by Maryland Vehicle Law subsection 13--411, Article 2.
Federal Vehicle Codes
While some states do not restrict side-mount plate use in any form, all motorcycles are subjected to federal requirements. According to the Federal Motor Vehicle Safety Standard 49 C.F.R. Subsection 571.108, Standard No. 108, all vehicles must have a source of illumination for the number plate itself.
If you own a motorcycle that uses a side-mount number plate, check with your local DMV to insure that you are operating within both state and federal laws. Violation of these laws is considered a traffic infraction by most states and punishable by fines up £910.