(a) As used in this Code section, the term "bridge" shall include the approaches to such bridge within 50 feet of either end except when the bridge itself measures 100 feet or more, in which case the term "bridge" shall include the approaches within 100 feet of either end of the bridge.

(b) Where the contract relates to the construction or reconstruction of all or a part of a bridge, the county or counties affected may require the successful contractor to add to the conditions of the performance bond required under paragraph (1) of Code Section 32-4-69 the following condition: to keep the bridge in good condition for a period of not less than seven years.