The Transit Network Design and Frequency Setting Problem (TNDFSP) can be defined as the creation of effective routes in a public transport network and the determination of relevant frequencies. Generally, the TNDFSP problem is in the same category as the Traveling Salesman Problem (TSP), which is known to be a non-deterministic polynomial-period (NP-hard) difficult problem. This study consists of two stages: first, the design of a public transport network with an evolutionary optimization technique - the Intelligent Water Drops (IWD) algorithm - based on the TSP and the determination of relevant frequencies; and second, the assignment of passengers to designated routes. All decisions related to public transport network design may be evaluated by considering environmental costs in relation to passengers, operators and the environment. This study presents an acceptable, constructive and original algorithm.