In 1950, plans were made to fill in the New Basin Canal, which the Belt Lines crossed on a bridge on Carrollton Avenue. The right of way was to be used for the Pontchartrain Expressway, and Carrollton Avenue traffic was to use an underpass. Rather than rebuild tracks in the underpass, the Tulane and St. Charles lines were separated, and Tulane Avenue was converted to a trolley coach line. During construction, the St. Charles line continued to operate (in both directions) all the way on Carrollton Avenue from St. Charles Avenue to the underpass construction site at Dixon Street. Once the underpass was completed, the St. Charles streetcar line was cut back to Claiborne Avenue, as it operates at present, and the Tulane trolley coach line took over the part of Carrollton Avenue between Tulane Avenue and Claiborne.