Any insurer who delivers or issues for delivery in this state liability insurance policies for motorcycles shall offer a premium discount on any such policy to any principal operator of a motorcycle who submits to such insurer proof of successful completion of the novice or advanced motorcycle training course offered by the Department of Transportation or other entity approved by the Commissioner of Motor Vehicles in accordance with § 14-40a. A minimum discount of ten per cent shall be applicable to premium charges for any such policy delivered, issued for delivery or renewed on or after October 1, 1987, such discount to be applicable for a period of five years from the original effective date of the discount. Such course shall be completed within one year prior to the initial application of the discount or, for subsequent applications of the discount, within one year prior to the expiration of the current discount period. If proof of successful completion of such course is submitted during the term of a policy, any premium modification shall become effective upon the next renewal. The discount provided by this section shall not be applicable to physical damage insurance coverage for motorcycles.