Abstract: Road information is an important element for a digital city. Modeling the overpass structure
is of great significance to many areas, such as the simulation of urban traffic, traffic optimization, and
urban planning. Although a great amount of research was conducted on the modeling of urban road
networks, a targeted solution for the treatment of overpass structures remained to be put forward.
Through the analysis of the overpass structure, a method for constructing overpass structures is
proposed based on the directed acyclic graph, with the purpose of realizing efficient and high-quality
modeling. Firstly, the two-dimensional raster data was preprocessed to extract effective road
information. Secondly, a directed acyclic graphs (DAG) was constructed to express the topological
relationship of overpass structure. Then, the height of each control point was calculated using the
proposed height calculation method designed according to the structural characteristics, functional
characteristics and related prior knowledge of the road. Finally, the overpass structure was
constructed, based on the calculated road height and topological information with component units.
The experiments selected three typical overpass structures in East China for testing. The results prove
that the proposed method is advantageous in data acquisition and calculation accuracy and can help
simplify the modeling process of overpass structures.

Key words: computer-aided modeling, heuristic modeling, urban road network, overpass structure, directed acyclic graph