Determination of Observation Weight to Calibrate Freeway Traffic Fundamental Diagram Using Weighted Least Square Method (WLSM)

Due to unbalanced speed-density observations, the one-regime traffic fundamental diagram and speed-density relationship models using least square method (LSM) cannot reflect actual conditions under congested/jam traffic. In that case, it is inevitable to adopt the weighted least square method (WLSM). This paper used freeway Georgia State Route 400 observation data and proposed 5 weight determination methods except the LSM to analyse 5 wellknown one-regime speed-density models to determine the best calibrating models. The results indicated that different one-regime speed-density models have different best calibrating models, for Greenberg, it was possible to find a specific weight using LSM, which is similar for Underwood and Northwestern Models, but different for that one known as 3PL model. An interesting case is the Newell\u27s Model which fits well with two distinct calibration weights. This paper can make contribution to calibrating a more precise traffic fundamental diagram

What leads to severe mountainous freeway crashes in southeast of China?

U radu je primijenjen hi-kvadrat test i binarna logistička regresija u analizi faktora koji dovode do teških sudara na brdskim cestama na jugoistoku Kine i određivanju njihova utjecaja na stupanj težine sudara u svrhu poduzimanja odgovarajućih mjera za poboljšanje sigurnosti na cesti. Rezultati su pokazali da mlađi i stariji vozači, žene, vožnja vikendom i rano ujutro, doprinose težini sudara. Uz to, vjerojatnije je da će se teški sudari dogoditi u proljeće, ljeto i jesen, nego zimi. Važnost dobivenih rezultata je u tome što vozači mogu razumjeti specifične karakteristike sudara na brdskoj autocesti na jugoistoku Kine te se mogu poduzeti odgovarajuće mjere da se stupanj sigurnosti poveća. Stoga se u radu daju sugestije za povećanje sigurnosti; mlađe i starije vozače treba upozoriti postavljanjem raznih prometnih znakova ili propagandom; vozačicama se savjetuje da ne voze na nekim dijelovima te ceste; upozorenja bi trebalo postaviti o pažljivoj vožnji noću naročito između 0 i 5:59 ujutro.This paper adopted chi-square test and binary logistic regression to analyse factors about mountainous freeway crash severity level in the southeast of China and to determine the factor impact on crash severity level to make corresponding measures to improve road safety. Results of this paper indicated that younger and older drivers, female drivers, weekends and driving early in morning all make contribution to severe mountainous freeway crashes. Besides, it is more likely to occur in severe crash in spring, summer and autumn compared to that in winter. The importance of study results to audience is that road users can understand the specific characteristics of mountainous freeway crashes in southeast of China and corresponding measurements could be made to improve the safety level. Therefore, this paper proposed some suggestions to improve mountainous freeway safety: younger and older drivers should be told the driving weakness by means of variable message sign or propaganda; female drivers are not encouraged to drive in some special mountainous freeway sections; traffic designs about careful driving at night are supposed to be set especially between 0 am and 5:59 am

Route Design Model of Feeder Bus Service for Urban Rail Transit Stations

As an important part of urban public transportation systems, the feeder bus fills a service gap left by rail transit, effectively extending the range of rail transit’s service and solving the problem of short-distance travel and interchanges. By defining the potential demand of feeder bus services and considering its relationship with the traffic demands of corresponding staging areas, the distance between road and rail transit, and the repetition factor of road bus lines, this paper established a potential demand model of roads by opening feeder bus services and applying a logit model for passenger flow distribution. Based on a circular route model, a route starting and ending at urban rail transit stations was generated, and a genetic algorithm was then applied to solve it. The Wei-Fang community of Shanghai was selected as the test area. Per the model and algorithm, the feeder route length was conformed to a functional orientation of short-distance travel and the feeder service of a feeder bus; the route mostly covered where conventional bus lines were fewer, which is a finding that is in agreement with the actual situation; the feasibility of the model and algorithm was verified

Sustainable Layout Planning Methods for Taxi Service Centres: A Case Study of Jiangning District, Nanjing

Taxi fleet size has undergone a continuous rapid growth in Chinese cities, while the service facility layout planning has relatively lagged behind, causing a decrease in the service quality. Therefore, it is crucial to carry out taxi service centre layout planning. This study analyses the functional orientation and hierarchical layout mode of taxi service centres, and then proposes stepwise layout planning methods combining existing transportation facilities. Considering the demand for integrated service centres is relatively low and convenient service centres are highly flexible, their layout can be determined by qualitative analysis. The constrained layout model of functional service centres is established by optimizing the layout scheme among various alternative taxi service centres. The study finds the model is a mixed 0–1 integer programming problem, genetic algorithms are applied to solve it. Finally, the proposed methods are applied to a real case of Jiangning district, Nanjing. The results show that one integrated service centre, four functional service centres, and twenty-three convenient service centres could satisfy taxi drivers’ demand, which suggests that the proposed methods should effectively address the layout planning problem of taxi service centres, thus have important implications for other cities’ downtown areas in China and beyond

Vortex Cascade Features of Turbulent Flow in Hydro-Turbine Blade Passage with Complex Geometry

A large-eddy simulation of three-dimensional turbulent flow for a hydro-turbine in the transitional process of decreasing load from rated power to no-load has been implemented by using ANSYS-Fluent in this paper. The survival space occupied by different scale flow structures for the different guide vane opening degrees was well captured. The flow characteristics in the transitional process were obtained. Different forms of the channel vortex were studied. The features of the vortex cascade and dissipation of the turbulent energy in blade passage were analyzed. The results show that the scales of the vortex structures have a large change in the transitional process of rejecting load, and the vortex distributions in the blade passage are significantly distinguished. The survival space of the different scale eddies in the blade passage is closely related to the scales of the vortex. The survival volume ratio of the adjacent scale vortex in the runner is about 1.2⁻1.6. The turbulent kinetic energy and eddy viscosity increase rapidly along the blade passage with the small-scale eddies going up, which implies that a dissipating path for the energy in the blade passage is formed

Modeling the Effects of Bus Stops on Bicycle Traffic Flow by Cellular Automata

Since currently huge traffic demands for public bus and bicycles exist in the majority of cities of China, it is highly likely that the bus stop has undeniable impacts on the bicycle flow that is close to the bus stop. In this paper, we proposed the test in several bicycle paths beside bus stops in Nanjing and aimed at exploring the specific effects of bus stop on the bicycle flow nearby. We assumed there were two such effects: space restriction and pedestrian conflicts. Further, we built up a cellular automation (CA) model to study the feature of these effects and find out not only the outcome of these two effects, but also the inner correlation between them

Traffic Status Dynamic Evaluation of an Eight-Lane Highway Based on the Lane Level

Traffic status analysis is the basis for highway management and control. Most of the previous research studies were carried out from the perspective of road segments. The purpose of this paper is to analyze the difference in traffic operation characteristics of an eight-lane highway from the perspective of lanes. Lane saturation, average lane speed, and lane density were selected as traffic state evaluation indicators, and the concept of state space division was introduced to classify the traffic operation status of each lane. Then, a single-system multi-index dynamic comprehensive evaluation method was adopted to reflect the time-varying characteristics and the development trend of the operation status of each lane. The research results can provide the theoretical support for more refined highway management and improve the service level of the eight-lane highway