Abstract
For functionally hierarchical road planning, it is important to set the appropriate target network defined by the number of road levels, road spacing and target travel speed of each road level, considering distribution of urban city centers, target travel time among them and demand characteristics. This study proposes a methodology to determine the variables that define target network based on the percentage of urban centers between which their target travel time is achieved as well as construction cost. In this methodology, target travel speed ratio is assumed to be proportional to road spacing ratio between two connected road levels, and the road levels with the highest or lowest target travel speed needs to be given in advance. These assumptions enable to limit the number of scenarios with realistic combinations of road spacing and target travel speed under the trade-off between mobility and access functions. Finally, a simple case study is conducted with a hypothetical grid network assuming some typical urban center distribution. As a result, the effects of number of road levels and target travel speeds on travel time by trip length and construction cost are demonstrated.
