In this paper, we propose a traffic model for a large-scale building giving careful consideration to traffic area. Our model consists of residential area, transportation area, and the rest. We focussed our attention on the trips generated between each pair of residents. There are three available transportation means in a building. The first one is a corridor to walk horizontally, the other two means, an escalator and an elevator, are used for vertical transportation. Each of the transportation means has its own capacity and speed, therefore the travel time and the necessary traffic area can be defined for each trip using it. We determine the distribution of residents as well as the transportation area which minimize the total travel time of trips under such constraints that the used area on each floor must be less than floor area S, and the population must be equal to a specified population P. Solving the problem, we can evaluate how the ease of mobility in a building changes as its size and proportion changes, from the viewpoints of travel time and required traffic area. We show two numerical examples in order to examine whether our model can properly describe the transportation capacity of an actual skyscraper. The first example is to approximate a district consisting of 10 skyscrapers in Shinjuku area. We calculate the travel time distribution of trips in the district using our model through carefully choosing model parameters. We compared it with the observed travel time distribution of 523 example trips, and find that our model approximates the actual district very well. The second example is to represent the elevator system in World Trade Center building in New York which uses express elevators and local elevators. An express elevator stops at the first floor, two predetermined floors halfway (skylobbies), and the top of the building. We derive a model for WTC building and try to find how this elevator system increases transportation capacity of a skyscraper. It is derived that it makes travel time from the entrance on the first floor to the whole building shorter and almost equivalent to those of the buildings lower by 30–40 stories. But it is not the case for a trip between points within a building. We also calculate the optimal location of skylobbies, which proved to be almost equal to the skylobbies in actual WTC building.
