text: Parking and traffic issues proved immensely vexing for the planners of Federal Triangle. The original L'Enfant Plan setting out the streets of Washington, D.C., still existed in the Federal Triangle area. Both C Street NW and D Street NW still ran from 15th Street NW to 15th Street NE.  Ohio Avenue NW ran in a northwest–southeast line from the intersection of D and 15th Streets NW to the intersection of B and 12th Streets NW (soon to be renamed as Constitution Avenue NW and 12th Street NW). Louisiana Avenue NW still ran in a southwest–northeast direction from 10th and B Streets NW to 7th and D Streets NW (along what is currently the diagonal portion Indiana Avenue NW). The McMillan Plan was developed before the widespread use of the automobile, and now the Board of Architectural Consultants had to decide how to accommodate the "horseless carriage" while also making Federal Triangle pedestrian-friendly. The Board began studying traffic issues in late 1927. A major study of parking needs and solutions was conducted in 1931, and traffic and parking patterns assessed again after the Department of Commerce building opened in early 1932. To achieve some of the traffic and parking goals, the east–west streets and diagonal avenues were eliminated, leaving only the north–south streets through the area, and 12th and 9th Streets NW were submerged in tunnels beneath the National Mall. In the first major change to the Board's "final" plans, the Grand Plaza was abandoned in favor of a parking lot. The Board considered a number of other solutions to the need to accommodate the more than 7,500 cars expected to arrive every day (including an underground bus terminal and underground parking garage under the Grand Plaza), but in the end only approved a small number of underground parking spaces beneath the Apex Building.