Exploring the impacts of intersection and traffic characteristics on the frequency and severity of bicycle-vehicle conflicts

This study proposes a conflict-based traffic safety assessment method by associating conflict frequency and severity with short-term traffic characteristics. Instead of analysing historical crash data, this study employs microscopic trajectory data to quantify the relationship between conflict risk and traffic characteristics. The time-to-collision (TTC) index is used to detect conflicts, and a severity index (SI) is proposed on the basis of time-integrated TTC. With SI, the k-means algorithm is applied to classify the conflict severity level. Then the severity of regional conflict risk is split to three levels. Zero truncated Poisson regression and ordered logit regression methods are employed to estimate the effects of short-term traffic characteristics on conflict frequency and severity, respectively. Furthermore, the copula-based joint modelling method is applied to explore the potential non-linear dependency of conflict risk outcomes. A total of 18 copula models are tested to select the optimal ones. The HighD dataset from Germany is utilized to examine the proposed framework. Both between-lane and within-lane factors are considered. Results show that the correlations between traffic characteristics and conflict risk are significant, and the dependency of conflict outcomes varies among different severity levels. The difference of speed variation between lanes significantly influences the conflict frequency and severity simultaneously. Findings indicate that the proposed method is practicable to assess real-time traffic safety within a specific region by using short-term (30-second time interval) traffic characteristics. This study also contributes to develop targeted proactive safety strategies by evaluating road safety based on conflict risk, and considering different severity levels.

Based on microscopic traffic characteristics of two-lane highway and different driving characteristics for drivers, the characteristics of drivers and vehicle structure are introduced into Cellular Automation model for establishing new Cellular Automation model of two-lane highway. Through computer simulation, the paper analyzes the effect of the promotion of different vehicles, drivers and arrival rates on traffic conflicts of two-lane highway, which gets the relationship between the parameters such as road traffic and velocity variance and collision. The results indicate that the frequency of traffic conflicts has close relationship with the product of traffic flow and velocity variation. When the traffic flow and velocity variation are great, the frequency of the conflict is the greatest, and when the traffic flow and velocity variation are little, the frequency of the conflict is the least.

In this paper, based on traffic flow characteristics of urban highways and discreteness 才 theory of numerical analysis, a series of traffic models including traffic generation model, car-following model, and lane changing models were built to study microscopic traffic flow simulation and calculation methods of urban road signal controlled intersections. Then a numerical simulation C++ program was coded on Linux platform using discrete mesh method after determining a reasonable traffic flow simulation parameters, and simulation results were verified using traffic survey data analysis. Finally, the basis for how to optimize urban road intersections congestion state and how to make decisions about traffic management and control of signalized intersections were provided, and the optimized way The urban transport system is composed of pedestrian, vehicles, roads, environment, and other factors. It is a dynamic system and it has complex structure, with multiple influencing factors, randomness, and unstable factors. In recent years, with the improvement of people's living standards, the urban vehicles and resident trips have been increased. This led to serious urban traffic congestion, dropped traffic speed, increased traffic accident rate, and environmental pollution. It has become a bottleneck that restricts the development of the urban economy. The intersections are the joints of the urban road network, and the study of the road intersection is the key to solve the traffic problems in the city. The actual capacity of intersection and vehicle delay time are an important indicator of the evaluating operation efficiency and service level of the intersection (1). In this paper, firstly, the intersection layout model, traffic generation and operation model, and signal control model were built to analyze the actual situation of the intersection and traffic characteristics. Then, based on these models, an urban road intersections traffic flow simulation program was developed and conducted with numerical simulation. Finally, the simulation model and modeling platform were verified by using a large number of field survey data. 2. Traffic Flow Modeling In this paper, traffic flow discrete model is considered in the fully discrete ideas of cellular automata and classic GM model (2) at the same time. Its basic idea is the road network will be divided into a number of square grids with the same size, length, and width of each grid representing certain distances. Roads are composed of several grids that merge together according to certain rules. The different grid cell represents a different size of vehicle. Grid length is defined as average space headway when blocked. The speed unit is m/s, the time step in this study is 1 second. CICTP 2015

Signalized intersections play a critical role in the motion of both urban and arterial streets. One of the basic parameters for the design and analysis of signal controlled intersections is saturation flow rate. This paper reports the estimation of saturation flow rate (SFR) considering the prevailing conditions in Egypt, at signalized intersections. Accordingly, three main objectives are stated for this study: The first one is to investigate the effect of the geometric and traffic characteristics on saturation flow rates. The second objective is to estimate a calibration factor for using US-HCM-2010 model to be suitable for the prevailing conditions in Egypt. The third objective is to develop a regression model for SFR considering intersection characteristics in Egypt.The required data for this study was collected at four signalized intersections in Shebin-Elkom city and in Tanta city using video recording technique. Geometric data and signal data were collected manually in the field. Data analysis showed that with the increase of the lane width, the saturation flow rate increases. The same conclusion can be extended to the turn-radius and vice versa with HV%. While comparing the saturation flow calculated from US-HCM-2010 with measured saturation flows, it is observed that the values aren't matching with the difference in values as 7.6%. After calibration, it can be seen that calibrated saturation flow based on US-HCM-2010 model is closer to the measured saturation flow with difference of 2.1%. Many regression models were developed for saturation flow rate considering intersection characteristics in Egypt. The best model has R2 equals 78%. This models includes 3 independent variables; %HV, lane width and lane type. The results indicated that, SFR measured using this model is closer to the field measured with a maximum difference of 1.2%. The model is valid for estimating the saturation flow rate at signalized intersections in Delta region of Egypt that have similar characteristics.

Transportation modes converge at intersections resulting in conflicts between bicyclists and motor vehicles. A common conflict and crash type involving bicycles at intersections is the right-hook, where a right-turning vehicle collides with a through bicyclist. While various geometric and signal control treatments have been used in attempts to mitigate bicycle–vehicle crashes and conflicts, agencies often face questions about optimal treatment selection. To date, limited research has been conducted to analyze how certain treatments (bike boxes, mixing zones, and bicycle signals) along with traffic characteristics (e.g., vehicle, bicycle, and pedestrian volumes) affect the frequency of bicycle–vehicle conflicts, as well as the severity of such conflicts. To address this research need, this study provides an analysis of bicycle–vehicle conflicts extracted from field-collected videos at 12 intersections; three with bike boxes, three with mixing zones, three with bicycle signals, and three control sites with no specific bicycle treatment. From these videos, bicycle–vehicle conflicts were identified and their severity measured using post-encroachment time (PET), along with conflict-involved road user speeds and hourly road user volumes. From these data, a series of Poisson regression models were estimated to assess hourly predicted conflicts as a function of bicycle and vehicle volumes across different treatment types. Additionally, differences in conflict severity across treatments were analyzed, including use of a novel measure which incorporates both PET and vehicle speed. Ultimately, several differences in conflict frequency and severity were observed between the treatment types, providing new data-driven guidance to assist practitioners in treatment selection.

Calibration of a micro simulation program for a Chinese city

Evaluating effects of traffic and vehicle characteristics on vehicular emissions near traffic intersections

Spatio-temporal dynamic change mechanism analysis of traffic conflict risk based on trajectory data

Traffic intersection characteristics with accidents and evacuation of damaged cars

The safety evaluation in the stage of acceptance inspection is the last safety inspection before highway operation, which is of great practical significance to minimize the traffic safety risk during the operation period. Collector-distributed first-grade highway mainly plays the role of collecting and evacuating traffic. It has the characteristics of many intersections and mixed traffic. Its traffic characteristics are complex, so traffic accidents occur frequently. Taking the safety evaluation of Leicheng connecting line of Donglei highway as an example, this paper analyzes and evaluates the main factors affecting the operation traffic safety of the collector-distributed first-grade highway, such as sight distance, clearance of highway, median divider opening, piers and abutments of upper-span bridges, speed limit scheme, and puts forward corresponding improvement suggestions, in order to reduce the accident rate during highway operation and ensure the safety and smoothness of highway traffic.

In this article, we estimate a Tobit model of property damage costs of crashes that occur at signalized intersections with data from one US city – Greensboro, North Carolina. The model includes data on technological variables, types of crash, types of vehicle, traffic and intersection characteristics, and driver condition at the time of crash. The results indicate that driver condition and type of vehicle contribute more to higher property damage costs than any other variable. Those variables that have negative effects on these costs are being a female driver, traffic volume, commercial and institutional land uses. From the results, we conclude that traffic countermeasures such as reducing the amber signal phase time and posting lower speed limits on urban roads could reduce property damage costs.

Traffic delay problems are manifesting in many of the major urban centres in Nigeria. The paper examined traffic delay problem and its causes at selected road intersections in Ilorin, Nigeria. The characteristics of the intersections that predispose them to delay problem and the spatial pattern of traffic delay at the road intersections were also identified. In addition, traffic volume and delay characteristics were estimated. Data were collected through direct field surveys on intersection characteristics, traffic volume, composition, delay causes and land use activities. The analysis of data collected revealed that variations exist in traffic flows and delays at the studied intersections. Also, traffic delays are discovered to be associated with the traffic volumes at the various junctions which ultimately translate to traffic congestion. Furthermore, traffic wardens and parking problems were found to be the greatest causes of delays at the road intersections in the city. The study therefore recommends that the road intersections be signalized and vehicle parking be strictly prohibited to reduce traffic congestion and delays at road intersections in the city.

An integrated clustering and copula-based model to assess the impact of intersection characteristics on violation-related collisions

This study presents a multiobjective evaluation method to estimate the performance of various midblock crosswalk treatments on urban streets. The considered objectives included traffic operation, traffic safety, environmental impacts, and costs. Data were collected at 16 midblock crosswalks in the Nanjing area in China. Vissim simulation models were developed and calibrated with field data to evaluate the operational and environmental impacts of various midblock crosswalk treatments. For the impact of various treatments on traffic operation, the total control delay to vehicles on the major streets and pedestrians were estimated. For the impact on traffic safety, the frequency of traffic conflicts was calculated. For the impact on the environment, vehicle emissions and fuel consumption were quantified. The TOPSIS entropy evaluation method was then used to rank the performance of various treatments of crosswalks considering multiple performance measures. Compared with the life-cycle cost analysis method that quantifies the benefits and costs using monetized expressions to establish a common unit, the TOPSIS method presented does not require the well-developed economic theories of valuation. It was found that by combining multiple objectives in decision making, one may obtain different results with regard to the optimum treatments of crosswalks. The research results can be directly used by traffic engineers to select crosswalk treatments given traffic flow conditions and geometric design characteristics. The framework implemented in the study can also be used to estimate the impacts of other traffic projects considering multiobjective evaluation.

Research on influence of sun glare in urban tunnels based on cellular automaton model in the framework of Kerner’s three-phase traffic theory