Generally, urban freeways connect the urban area to the suburban areas or circulate along the circumference of the suburban areas in the big city. Today most of the urban freeways are experiencing a severe congestion with the mixed traffic on the on-ramp junction during the peak periods.
The purpose of this study was to identify the real-time traffic characteristics, construct the speed-density models depending on the areas and the directions and finally verify the models constructed. From the analyses of the real-time traffic characteristics, and the construction and verification of the speed-density models, the following results were obtained:
ⅰ) Real-time traffic characteristics(flow, speed, occupancy, the mixed rate of the medium and large vehicles, etc.) in the urban freeway on-ramp junctions under the study showed a distinct difference depending on the time periods, the on-ramps and the directions. Especially, they did a big difference depending on the closeness of the urban area during the peak periods.
ⅱ) The mixed rate of the medium and large vehicles in the urban freeway on-ramp junctions under the study were shown to be an important factor in the analyses of the real-time traffic characteristics and the construction of the speed-density models by showing a considerable difference depending on the time periods.
ⅲ）Constructing the linear speed-density models in the urban freeway on-ramp junctions under the study showed a considerable explanatory power with the determination coefficients of over 0.70 between the speed and the density data based on the real-time traffic characteristic data.
ⅳ) Verifying the linear speed-density models constructed in the urban freeway on-ramp junctions under the study also showed a considerable correlativeness with the correlation coefficients of over 0.83 between the observed speed data and the expected speed data estimated by the linear models constructed.
Thus, it was concluded that the linear modeling would be considerably valid in the analysis of the speed-density relationship on the urban freeway on-ramp junctions in the country.