All motor carriers of passengers and baggage subject to 49 U.S.C. subtitle IV, part B, which provide in their tariffs for the declaration of baggage value in excess of a free baggage allowance limitation, shall provide for the declaration of excess value on baggage at any time or place where provision is made for baggage checking, including (a) at a baggage checking counter until 15 minutes before scheduled boarding time, and (b) at the side of the bus or at a baggage checking counter in reasonable proximity to the boarding area during boarding at a terminal or any authorized service point.