Estimation of Critical Gap Using Maximum Likelihood Method at Unsignalized Intersection: A Case Study in Adama City, Ethiopia

Critical gap through clearing behavior of drivers at unsignalised intersections

Roundabout Capacity in Heterogeneous Traffic Condition: Modification of HCM Equation and Calibration

Critical gap is an important parameter which affects the capacity and delay of unsignalized intersections. There are different critical gap values for drivers in different geometry parameters and traffic conditions. Critical gap is generally considered to follow Erlang distribution, lognormal distribution, etc. Various methods calculating critical gap of roundabouts have been presented. Many studies on gap acceptance at roundabouts have been carried out in America, Australia and some countries in Europe; whereas the same works have rarely been done in China. This paper gives an overview of many methods calculating critical gap. On the base of video survey of Shuma Square roundabout in Dalian, we acquired a large number of rejected gaps and accepted gaps in rush hour. Critical gap can be calculated by use of different methods including Ashworth's method, Raff's method and the maximum likelihood method (MLM). As a result, the maximum likelihood method and the revised Raffs method can be recommended for practical application, and Ashworth's method will result in larger result because it only uses values of accepted gap.

Entry Capacity Quantifying Model through Drivers’ Behavior at Roundabouts

Under mixed-mode traffic conditions prevailing on Indian roads at unsignalized intersections, it is commonly observed that vehicles entering from minor streets indulge in forceful gap creation/delay for the vehicles moving on the major road. Although this driving behavior has been reported in some of the published studies for Indian traffic conditions, a clear definition of such forceful entries is not available. An attempt has been made in this study to define this forceful entry phenomenon on the basis of changes in the speed of major streets’ vehicles approaching the intersection on a typical case of mixed-traffic environs. In this regard, field observations were recorded through videography to obtain the speed reduction threshold value for categorizing an entry as a forceful entry. To quantify the above, data in relation to various vehicle types approaching intersections and their associated speeds at the reference area were extracted at the approach arms of the intersection. On the basis of observations, collected data were divided into three scenarios: ( 1 ) vehicles on major roads reduce their speed when vehicles are absent on minor roads; ( 2 ) vehicles on major roads reduce their speed when vehicles are waiting on minor roads; and ( 3 ) vehicles on major roads reduce their speed when vehicles from minor roads have accepted the gap/lag for movement. The changes in speed in all the three scenarios were compared to identify forceful entries with the base case of normal traffic flow on the major road without the existence of forceful entry phenomenon. The study revealed that the speed reduction to the extent of 73% is considered as a forceful entry at the selected location. Furthermore, the study estimated the effect of forceful behavior on critical gap at unsignalized intersections.

Gap acceptance is the main parameters of intersection capacity and safety research. Although the domestic and foreign scholars and researchers have studied the critical gap deep in the capacity researches, very few paper has been discussed the process of gap acceptance from the view of traffic safety behaviors. The objective of this paper is to analyze the safety behavior of gap acceptance, to examine the relationship between gap acceptance behavior and waiting time, and to make suggestions of safety traffic control design for unsignalized intersections. The authors observed 1216 left-turn gap-acceptance behavior samples from 11 tee type of unsignalized Intersections, which are two ways four lanes in majors and two ways two lanes in minors (i.e. 4 x 2 T Intersections). It is found that some drivers' gap-acceptance behaviors change along with their waiting time. It is also found that the precision of the traditional prediction model for critical gap could be improved if waiting time is considered, which implies that drivers' gap acceptation behaviors have much to do with drivers' waiting time. The waiting time is longer, and the possibility of taking risks to accept the small gap is larger. The quantitative model was also developed to explain the relationship between values of accepted gap and waiting time.The conclusions of paper are expected to be useful in safety control design and discussing safe driving behavior for unsignalized intersections.

Walking is the basic mode of transportation in India. It is considered as one of the feasible and eco-friendly mode of transportation. Pedestrian crossing at an urban uncontrolled intersection is unsafe for pedestrians because of dynamic movement of pedestrians. The objective of the study is to analyse the pedestrian behaviour at an urban uncontrolled intersection considering quantitative and qualitative parameters by estimating critical gap and also considering the accepted and rejected gaps by the pedestrians. The impact of traffic characteristics as well as demographic characteristics of pedestrians for instance gap size, type of vehicle, age, group size, gender, etc., is studied to analyse the crossing behaviour of pedestrians at an uncontrolled intersection. The estimation of critical gap has been done using Raff’s method, which is a deterministic approach. Furthermore, the machine learning approach (ANN) is used to model the pedestrian decision making behaviour at an uncontrolled intersection.KeywordsPedestrian characteristicsUncontrolled intersectionCritical gapArtificial neural networkCrossing behaviour

For the estimation of critical gaps for unsignalized intersection analysis, the so-called maximum likelihood method currently is treated as the best approach. This paper demonstrates that the maximum likelihood method is a special case of the more general mathematical survival theory for the estimation of interval-censored parameters. The assumption of a special mathematical type for the statistical distribution of critical gaps is an essential part of the method. Test applications with various types of functions show that the results do not significantly depend on the applied type of distribution. Therefore, the traditional lognormal distribution is not an essential part of the theory. Instead, it is reasonable to apply that type of distribution that can be handled more easily. From this standpoint, the logistic distribution is favorable. Because the variance of each kind of distribution of the critical gaps does not contribute to the precision of the result, a simplified method is useful if the standard deviation of the critical gaps can be predefined and if only the scale parameter of the function is adjusted to the measured gap data. The results from this single-parameter method are rather congruent with those from the more complicated two-parameter method. The simplified approach opens the way to apply critical gap estimation in traffic engineering practice to adjust capacity calculations to local driver behavior.

Aim of study: The aim of this work was to model diameter distributions of Quercus suber stands. The ultimate goal was to construct models enabling the development of more affordable forest inventory methods. This is the first study of this type on cork oak forests in the area.Area of study: The area of study is “Los Alcornocales” Natural Park (Cádiz-Málaga, Spain).Material and methods: The diameter distributions of 100 permanent plots were modelled with the two-parameter Weibull function. Distribution parameters were fitted with the non-linear regression, maximum likelihood, moment and percentile-based methods. Goodness of fit with the different methods was compared in terms of number of plots rejected by the Kolmogorov-Smirnov test, bias, mean square error and mean absolute error. The scale and shape parameters in the Weibull function were related to the stand variables by using the parameter prediction model.Main results: The best fitting was obtained with the non-linear regression approach, using as initial values those obtained by maximum likelihood method, the percentage of rejections by the Kolmogorov-Smirnov test was 2% of the total number of cases. The scale parameter (b) was successfully modelled in terms of the quadratic mean diameter under cork (R2 adj = 0.99). The shape parameter (c) was modelled by using maximum diameter, minimum diameter and plot elevation (R2 adj = 0.40).Research highlights: The proposed model diameter distribution can be a highly useful tool for the inventorying and management of cork oak forests.Key words: maximum likelihood method; moment method; non linear regression approach; parameter prediction model; percentile method; scale parameter; shape parameter.

Along with the increasing population and increasing development in all sectors in Mataram City every year, resulting in an increase in the volume of vehicles which often causes potential traffic conflicts. This condition results in disturbances for motorists in the flow of vehicles on the u-turn facility so that it affects performance on the road. One of the roads in the city of Mataram that is the choice in the travel route for the community is Jalan Sriwijaya. It is necessary to review the performance of roads with median openings, especially on unsignalized roads and intersections.The method used in this study is the calculation of urban road performance using MKJI 1997. Data from the location of median openings on unsignaled roads and intersections were collected through a field survey and then calculated the average traffic flow, average speed, average turning time average, capacity, degree of saturation, and level of road service. The results of the analysis show that the average traffic flow that occurs on the Sriwijaya road is 864.73 pcu/hour with a capacity of 2737.15 pcu/hour and the degree of saturation (DS) is 0.316 so that it is classified as a service level "B", while the average traffic flow at the unsignalized intersection is 2441.77 pcu/hour with a capacity of 4199.91 pcu/hour and a degree of saturation (DS) value of 0.581 so that it is classified in the "C" service level. The average turning time on roads is 8.04 seconds and at unsignalized intersections 6.94 seconds.

Investigating the safety and operational benefits of mixed traffic environments with different automated vehicle market penetration rates in the proximity of a driveway on an urban arterial

Unsignalized intersection Jl. Raya Cangkiran - Jl Cangkiran Gunung Pati, Tambangan kec.Mijen, Semarang is a three-way intersection that has access to the Cupan Terminal. Many people pass through this intersection. In conditions at these intersections, traffic jams occur during rush hours, and there is no traffic light which makes traffic conditions even more irregular, the safety of motorists is also threatened. Therefore, this study was carried out to analyze unsignalized intersections, planning the use of traffic lights, and knowing the traffic characteristics of Jl. Raya Cangkiran - Jl. Gunungpati Cup, Semarang. Data collection was carried out for 3 days, namely Saturday 25 February 2023, Monday 27 February 2023, and Wednesday, 1 March 2023 by taking peak hours at 06.00 WIB - 08.00 WIB, 12.00 WIB - 13.00 WIB, and 16.00 WIB - 18.00 WIB. Data collection methods used are capacity, degree of saturation, delays, queue opportunities, and Traffic Signaling Devices (APILL). The performance analysis of this unsignalized intersection uses the 1997 Indonesian Highway Capacity Manual (MKJI) to calculate the degree of saturation. As for the level of service using the Minister of Transportation Regulation No. 96 PM 2015. The results of the research are that in the existing conditions, alternative B is chosen as the best alternative for planning traffic lights with 2 phases of the 1-hour peak scenario on Saturday morning with a degree of saturation of 0.823 pcu/hour, a queue length of 103,045 m on the West approach, and a value delay of 14,784 veh/sec. From the results of the analysis, it can be concluded that the results of calculating the traffic evaluation for the current conditions obtained that the highest vehicle volume occurred on Monday, 27 February 2023. Then Jl. Raya Cangkiran – Boja, Semarang, fulfills the criteria for installing traffic lights and needs to install traffic lights or traffic control lights. As well as from the 3 planned alternatives, alternative B was chosen to install a 2-phase traffic signal light.

Analysis of snow load probabilistic models and calculation of reference snow pressure using maximum likelihood method for multiple cities in Liaoning Province, China

The issue of road accidents is an increasing problem in developing countries. This could be due to increasing road traffic/vehicle occupancy, geometric characteristics and road way condition. The factors influencing accidents occurrence are to be analysed for remedies. The purpose of this research is to develop an accident prediction model as a measure for future study, aid planning phase preceding the designed intervention, enhance the production of updated design standards to enable practitioners design unsignalized intersection for optimal safety, reduce the number of accidents at unsignalized intersections. Five intersections were selected randomly within Benin City and traffic count carried out at these intersections as well as geometric characteristics and roadway conditions. The prediction model was developed using multiple linear regression method and the standard error of estimate was computed to show how close the observed value is to the regression line. The model was validated using coefficient of multiple determination. The establishment of the relationship between accidents and traffic flow site characteristics on the other hand would enable improvement to be more realistically accessed. This study will also enhance the production of updated design standards to enable practitioners design unsignalized intersection for optimal safety, reduce the number of accidents at unsignalized intersections.

Significant social, economic, and environmental costs are associated with traffic congestion. The effectiveness of intersections makes a substantial contribution to the effectiveness of entire road networks. The three-leg at-grade Al-Husainea intersection, located 20 km from the center of holy Karbala city in Iraq, is subjected to serious congestion, resulting in an increase in delay time, reduction in capacity, and bad level of service (LOS). Therefore, it is essential to use advanced software tools to ensure that the current intersection can be controlled, evaluated, and improved. So, the major goal of this study is to use SIDRA, an acronym for signalized and unsignalized intersection design and research aid, software to evaluate the LOS of the Al-Husainea intersection, in which the traffic is assessed using the current LOS. LOS, delay time, and degree of saturation were the criteria utilized to evaluate the traffic flow performance. SIDRA is also used to assess benefits as a result of suggested changes in the design of particular junctions. The first stage is to gather field data regarding traffic volumes utilizing a method of traffic volume gathering. From 7 am to 6 pm, the SIDRA program gathered data for a full 7 days. The results showed that the LOS for the Al-Husainea intersection in the Al-Husainea arm is F, with an average delay of 52 s per vehicle and a saturation level of 0.86 v/c. Finally, it was determined that the Al-Husainea intersection needs additional improvements based on the study and findings from the SIDRA program, and some remedies are suggested in this study to improve the intersection traffic flow.