Abstracts:To analyze and compare the vehicle performance effects of hydraulic bushings with those of the traditional rubber bushings of double wishbone front suspensions, we test the static and dynamic properties of the hydraulic bushings of control arms. The mechanical model is built in ADAMS and is then used as the basis for establishing the full vehicle model. The random road surface spectra of different levels are built using the harmony superposition method. The ride comfort of the full vehicle with a control arm installed with hydraulic and rubber bushings is simulated on random and bump roads. The frequency spectrum characteristic and root mean square (RMS) of the vertical and longitudinal acceleration of the foot floor and seat rail are calculated via power spectrum estimation, and the handling stability of the full vehicle is then simulated. The effects of the change in hydraulic bushing stiffness on ride comfort are finally analyzed. The following results are obtained. (1) The effects of such change on vehicle handling are relatively small regardless of the type of bushing used. (2) The vehicle shows acceptable ride comfort on level A and level B roads but shows poor ride comfort on bump road when a hydraulic bushing is used. (3) Large hydraulic bushing stiffness increases the vertical acceleration RMS on level A, level B, and bump roads. However, the variety of RMS is extremely small on level D roads, the responses of the vertical and longitudinal acceleration curves are slow, and the time oscillation of the curves is relatively long on bump road.

Abstracts:Given that dynamic test data are difficult to obtain and relevant test results are always unstable, this study examines the rollover crash worthiness of a 6756-type bus. The finite element model and numerical simulation environment for the rollover crash are established in the LS-DYNA software according to the ECE R66 regulation to analyze the dynamic numerical simulation results of the rollover crash of the passenger vehicle. This study discusses and analyzes the energy dissipation of the system, the energy-absorbing effects of the main structure, and the deformation of the system in the rollover crash process. The effectiveness of the method that evaluates the rollover crash of the passenger vehicle with finite element is verified by comparing the simulation results and the real vehicle testing data. Results show that the amounts of absorbed energy of the right side, top, and left side walls of the passenger vehicle account for 40%, 30%, and 15% of the total absorbed energy, respectively. The deformation of the column in the same window successively decreases from top to bottom, and the deformation of the column with the same height in different windows decreases from the front to the back.

Abstracts:This second part of the study is a followup to Part I. In addition to the Asset Condition Index (ACI) establishments and statistical model estimates of the first part, this further study analyzed several typical asset improvement methods, which placed priority on safety. This study used data that were identical to those in the previous study, i.e., the one-mile-segment data set for all state primary roads from 2004 to 2009 integrated using geographic information system (GIS) tools. With the estimated ACI and the separate models, this study focused on developing a methodology to prioritize safety improvements based on asset conditions. Results indicate that minor rehabilitation and durable material marking have the highest B/C ratio when a one-year analysis period is considered. To expand the analysis for 5 years, a decision-making matrix of ACI ranges versus treatment alternatives was developed.

Abstracts:Overtaking probability formula in the Prigogine—Herman traffic flow mesoscopic model is the function of traffic density, which is a linear function and does not consider overtaking requirements. In this paper, we use desired speed to improve the overtaking probability formula and propose a new overtaking probability formula that is nonlinear and a corresponding traffic flow mesoscopic model. The improved model can simultaneously consider traffic density and overtaking requirements, thus reflecting traffic flow operation realistically. We use the proposed model to simulate the diffusion process of vehicles from a high-density section to a low-density section. The example analyzes the difference between the linear overtaking probability formula and the parabolic Greenshield’s overtaking probability formula. Results show that the linear overtaking probability formula evolves quickly and converges to three speed classes. The parabolic Greenshield’s overtaking probability formula converges to six speed classes and can reflect speed distribution evolution reasonably.

Abstracts:A system dynamics (SD) model of the sustainable development of urban transport is built with vehicle development policy considered as the regulating factor. Moreover, an empirical study is conducted using SD and integrating environmental factors. Results show that (1) policy intervention influences the indicators of vehicle possession, gross domestic production, total population, and pollution index of ${\mathrm{NO}}_2$; and (2) strict restrictions on vehicles can effectively relieve traffic congestion, reduce the percentage of vehicle travel and trips, and urge people to shift from private to public transport. Policy intervention also improves the service level of public transport. The negative effect of urban transport development on the environment can be reduced. A restriction policy on vehicle possession should be implemented. Moreover, research, development, and promotion of effective energy-saving measures and emission-reducing technologies are needed to reduce energy consumption and emissions from vehicles.

Abstracts:The optimization of transit network can improve transit efficiency and traffic conditions as well as reduce environmental pollution. Transit network optimization that considers the travel behavior of bus passengers comprises four steps. First, a bypass strategy is employed to optimize the bus lines according to the situation of urban traffic congestion. Second, direct ratio is calculated to determine the optimal network. Third, minimum transfer is sought by using the space P method to construct and analyze a transit network model. In building a network adjacency matrix, the Floyd algorithm is used to obtain the matrix of minimum transfers between two stops. The Breadth-First Search algorithm is used to search the bus routes with the shortest transfer time. Fourth, all the bus lines of the same origin-destination are optimized to obtain the shortest travel time. Numerical experiments show that the proposed method can reasonably and efficiently achieve network optimization within a given area.

Abstracts:A video-based traffic flow detection system requires calibration of cameras to generate accurate estimates of vehicle speed. Traditional manual calibration methods cannot satisfy this requirement because calibration has complex procedures. A new traffic camera calibration method is proposed, which exploits reference images and roadway information. The proposed method requires only two parallel lane markings with a known width and a line perpendicular to the lane markings. Camera parameters, including focal length, tilt angle, pan angle, and camera height, can be recovered. A method based on reference images is further proposed to calculate ill-conditioned camera parameters, in which reference images are acquired by a rotating camera while keeping focal length unchanged. Camera recalibration can be easily realized through reference images and roadway information when cameras are moved manually. Simulation experiments demonstrate that the proposed method has the advantages of simple operation and accurate parameter estimations. The method also requires no manual operations and saves manpower.

Abstracts:Signal control of urban, intersections still mainly employs single-point fixed phase, and optimal timing methods cannot optimize traffic given the altering state of traffic flow. To address these issues, the phase of optimal flow line combination is dynamically generated with the principle of traffic flow line compatibility and minimum loss of green light and according to the traffic flow at the intersection entrance. After ascertaining the combination of the periodic phase, the vehicles’ average delay of traffic flow lines is analyzed when the vehicles are detained (or not detained) in the traffic flow line at the end of the period. Combined with the delay model, the optimal timing model, which can adapt to the dynamic changes in intersection traffic flow, is established. The optimal timing of phases is calculated to achieve dynamic optimization control of the intersection traffic line. The calculation example shows that the delay is small and the improvement of intersection running state is highly effective when the optimal timing model based on dynamic control of traffic flow is employed.

Abstracts:To forecast the tunnel surrounding rock category quickly and effectively and to enhance the stability of underground engineering and security, we apply theory of factor analysis and Fisher discriminant analysis. In addition, six indicators, namely, rock quality, integrity, saturated uniaxial compressive strength, longitudinal wave velocity, elastic resistance coefficient, and structure surface friction factor, were selected as discriminant factors in Fisher’s discriminant analysis. A Fisher prediction model based on factor analysis was built to predict the tunnel surrounding rock category. Thirty groups of tunnel surrounding rock data in the survey site were used as learning samples for the training. The resubstitution method was used to test the model, which yielded a 96.7% accuracy. The established discriminant model was used in an engineering application and used six sets of engineering data as test samples to forecast the classification of tunnel surrounding rock. We also compared this model simultaneously with the neural network and Bayes methods. The factor analysis can effectively extract the surrounding rock classification index and remove the redundant factors. Fisher’s discriminant model based on factor analysis can effectively predict the tunnel surrounding rock category with 100% prediction accuracy.

Abstracts:Regulations on relevant design specifications are comparatively analyzed to expediently calculate the carrying capacity of the cross section of the bending member of a bridge reinforced with an enlarged section. Five different failure forms of the bending member strengthened with the enlarged section are analyzed, along with the advice on modifications propounded by some experts and professors who apply the said regulations. Results lead to the conclusion that the B-class failure form of a suitable reinforced beam is impossible. This failure occurs when new tension steels do not yield but old tension steels do yield. Based on the conclusion of the present study on damage forms, the calculation formula for the carrying capacity of the cross section of bending beams strengthened with enlarged sections is obtained, and the scope of application is extended to increasing the concrete sections on the tension and compressive zones, as tested by engineering examples. The calculation method is simple and relatively safe and has already been adopted in the Technical Specifications for the Strengthening of Urban Bridges, which will be enacted soon.