In this paper, a new analytical model is proposed to determine optimal frequency for urban bus transit under variable demand by explicitly considering the interaction between different vehicles in urban mixed traffic. The effect of road congestion on in-vehicle travel time associated with each mode is explicitly considered in the formulation of link performance function. The equilibrium flow of vehicle in mixed traffic and the passenger flow on the transit network are computed using multi-modal equilibrium assignment with respect to the frequency selected by Hooke-Jeeves algorithm; finally, the optimal frequency is found by repeating the process. A numerical example is given to illustrate the application of the model and algorithm. From the convergence test and sensitivity analysis, some important conclusions are drawn. The computational result proves that the proposed model is applicable in real aspects of bus network design in mixed traffic.
This study probes into the promotion policy for improving the willingness of students to walk or cycle to school. The intentions of elementary and junior high school students as well as their parents in selected schools in Tainan, Taiwan were surveyed. The feasibility of reducing BMI through walking/cycling to school is evaluated through a System Dynamic (SD) model which is capable of calculating the calories consumed, accumulated, and the effect of walking/cycling on BMI. With practical data to show weight control effect, the model shows that weight control program can be replaced effectively by walking to and from school. In addition, to promote walking/cycling to school, tree planting on wayside and adding the pathways and bicycle lanes are the desired conditions for walking and cycling respectively.
This study aims to identify mid- and long-term characteristic congestion trends in the urban area by classifying time-series data collected at sensor-installed points using the k-means method a major unsupervised clustering technique, and to support measure planning for each point using the results obtained from the classification. In this study, temporally and spatially characteristic congestion patterns were extracted from a large amount of congestion data obtained from sensors installed at approximately 2,200 locations across Sapporo urban area. The identification of regular congestion patterns that occur at certain locations and hours is expected to facilitate support for the planning of traffic measures that require temporal and spatial consideration. As the result of this study, congestion trends and congestion-point distributions in the city were then classified into a number of patterns, allowing the selection of effective measures and the identification of targets for countermeasures.
Intelligent Transportation Systems (ITS) focus on increasing the efficiency of existing surface transportation systems through the use of advanced computers, electronics, and communication technologies. The interaction between signal setting and traffic assignment is an important issue in designing efficient ATMS. This research focuses on finding dynamic user equilibrium between signal setting and route assignment. The problem is solved through a bi-level framework. The upper level solves for signal setting parameters, including cycle length, green splits, and offsets. The lower level solves for user equilibrium Dynamic Traffic Assignment (UEDTA) flows in a traffic network. The signal setting is adjusted through two methods: the Webster formula and Adaptive Signal Control. UEDTA flow patterns are solved through a simulation-based DTA model, DynaTAIWAN. This bi-level framework can be applied in cities with signalized networks. Numerical experiments are conducted based on a sub-network of Kaohsiung City to illustrate the proposed framework.
The current loss-time estimation and intergreen time design methods in Japan lack sufficient consideration of the characteristics of right-turn traffic, such as right-turner's behavior as well as clearing distance and speed under various phases. Utilizing field data, this paper first examined loss-time estimation method under the permissive-and-protected right-turn (PPRT) and protected-only right-turn (PORT) phasing plans. Results showed that the current method is very likely to over-estimate loss time. Two modifications to the current method for the PORT and PPRT phasing plans, respectively, were then proposed to provide more accurate and sophisticated estimation. Meanwhile, intergreen time design method was examined. It was found that the current method tends to generate unnecessarily long all-red times for right-turn traffic as compared with German method. Thus, it is suggested that the applicability of the German method to Japan conditions needs to be investigated to reduce loss time as well as cycle length.
In order to provide reliable travel time information by probe vehicle system, a huge amount of travel time data should be collected. To minimize cost of data collection from probe vehicle with certain reliability level, the number of required probe vehicles and its optimal regional allocation should be examined. Therefore, this study proposes a new methodology to estimate the number of probe vehicles required to ensure the reliability of travel time estimation. It aims to verify the feasibility of reducing the number of probe vehicles from that required by the conventional methodology. Also, the feasibility of reducing probe vehicles by estimating travel time with existing traffic detectors is verified. The study concluded that the required number of probe vehicles estimated by the new methodology is less than that estimated by the conventional methodology, and that the use of probe vehicle systems leads to quick development of traffic information collection system.
The temperature variation of the concrete pavement in the early age significantly affects the initiation and propagation of its early age cracks. The measurement and analysis of early age temperature trend are necessary to examine the causes of early age cracks in the jointed concrete pavement (JCP). In this study, it is investigated how the early age temperature trend in the concrete pavement affects the random crack initiation and behaviors of saw-cut joints using the KEC test road. After placing the concrete pavement, the ambient air temperature and temperatures in the concrete pavement were measured and the random crack initiation in concrete slabs and early behaviors in the joints were surveyed. The results indicate that the first random crack was initiated at one of the slabs placed in the early morning. In addition, the joints that were saw-cut in the morning were cracked more rapidly than those saw-cut in the afternoon.
Porous asphalt mainly rely on the binder content and binder properties for cohesion between aggregate particles where good cohesion would increase resistance to permanent deformation like raveling and stripping. This paper presented the results of a Cantabro Abrasion Loss Test on rubberized porous asphalt. Specimens were prepared with different percentages of binder content, rubber content and mixing process namely wet process and dry process. Two kinds of samples, an air-cured sample and a water-soaked sample, were used to simulate raveling and stripping respectively. Results indicated that the incorporation of a low amount of rubber resulted in better abrasion resistance in wet mixing process, while resistance to abrasion increases as rubber content increase on samples prepared by a dry mixing process. The study showed that dry process samples were more effective than wet mix samples in reducing abrasion loss for both conditions of sample.