A theoretical analysis of delays at an uncontrolled intersection

This paper compares per-mile risks posed by motor traffic to pedestrians and cyclists on urban major and minor roads. Carrying out new analysis of police injury data from 2005 to 2015, this study finds that per billion vehicle miles, motor vehicles on minor roads create more pedestrian casualties than motor vehicles on major roads. Specifically, for killed or seriously injured (KSI) casualties the rate per billion motor vehicle miles is 17% higher on minor roads (47 against 40 KSIs per billion vehicle miles), while for slight injuries it is 66% higher (188 against 123 slight injuries per billion vehicle miles). Examining the costs of injuries sustained, these are 7·4% higher for pedestrians per motor vehicle mile travelled on urban minor roads, compared with major roads. For cyclists, injuries per mile driven are similar on major and minor roads. These results suggest that re-routing motor traffic to major roads in urban areas may reduce pedestrian casualties. Cyclist safety on major roads should be improved to avoid unintended negative consequences and ensure positive outcomes for cycling.

Since 2006, INDOT has been preparing an annual five‐percent report that identifies intersections and segments on Indiana state roads that require attention due to the excessive number and severity of crashes. Many of the identified intersections are two‐way, stop-controlled intersections located on high‐speed, multi‐lane, rural roads. Some contributing design and human factors have been identified while other factors still await investigation. Multivariate ordered probit models have been developed to help identify additional factors of the frequency and severity of crashes. These models can estimate how much different factors increase the frequency of crashes at several levels of injury severity (fatal/incapacitating, non‐incapacitating/ possible, property‐damage‐only). They have a unique ability to account for unobserved but common conditions that affect all of the crash severity levels. Recommendations for safety countermeasures are made based on both of these research results and our study of published reports of other authors. The statistical analysis was performed on 553 existing intersections in Indiana and 72 existing intersections in Michigan using crash data reported during a four‐year period. The identified safety factors include: presence of horizontal curves within the intersection vicinity, traffic volume on the major road, land use, population of the area surrounding the intersection, and the minor road functional class (traffic volume on minor road unknown), nearby at‐grade railroad crossings, intersection conspicuity to drivers on the major road, acceleration lanes for both left and right turns, median width, intersection angle, and number of intersection legs. These results are in line with other research results as documented in the literature review. Based on the results of this and other studies, recommendations are made to improve safety at new intersections as well as at existing intersections. For new intersections, construction of medians wider than 80 feet is suggested. Where this is not possible and a narrower median needs to be constructed, adding a parallel acceleration lane for vehicles turning left from the minor road is suggested. Intersections should be placed at a sufficient distance from horizontal curves and from at‐grade railroad crossings. Solutions with indirect left-turn lanes (Michigan U‐turns, J‐turns) are recommended. At existing intersections experiencing excessive numbers of crashes involving vehicles from the minor road, median closure should be considered or a median opening should be restricted to certain maneuvers. Median acceleration lanes can be added in order to allow a two‐stage maneuver for left turns from the minor road. Enhanced guide and warning signage can be used to improve intersection conspicuity; adding road illumination can especially help at night. The practice of adding left‐ and right‐turn bays should be continued as this is a proven intersection safety improvement practice. Applying these countermeasures may help improve safety and avoid the construction of expensive grade separations. Finally, advanced intersection collision avoidance systems, such as road‐side dynamic signs warning drivers on the minor road about a short gap on the major road, should be the subject of pilot studies in Indiana. Experiments in other states have indicated that these systems help drivers choose safe gaps.

Automatic road identification and labeling in Landsat 4 TM images

This paper focuses on the effects of mixed traffic circumstances of uncontrolled or unsignalized intersection under heavy flow when traffic is heterogeneous in character. On the basis of field data collected on Fuljhore road, Durgapur, it is clear that capacity reduces if the proportion of slower vehicles increases in the traffic stream. On the basis of field data collected, the present study also made it evident that the speed data deviate from the normal distribution curve and skewness of speed data is significantly high under the high density of traffic flow. The present study, therefore, examined the distribution of these data and concluded that their logarithmic transformation reasonably satisfies the normality assumption while modeling in terms of goodness-of-fit. Modeling traffic flow through urban uncontrolled intersections in developing countries like India is a complex process because of the high-level heterogeneity of traffic and absence of major and minor road concepts in traffic regulation schemes. Moreover, Indian codes have not been provided any relation which can be used to directly determine the delay at uncontrolled intersections under Indian traffic conditions. Uncontrolled intersections are vital points on urban roads, the performance of which will influence the flow of traffic on the road network.

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.

Many traffic accidents are caused by unforeseen and unexpected events in a site that was hidden from the driver's eyes. Road design parameters determining required visibility are based on relationships formulated decades ago. It is worth reviewing them from time to time in the light of technological developments. In this paper, sight distances for stopping and crossing situations are studied in relation to the assumed visual abilities of autonomous vehicles. Current sight distance requirements at unsignalized intersections are based among others on speeds on the major road and on ac-cepted gaps by human drivers entering or crossing from the minor road. Since these requirements vary from country to country, regulations and sight terms of a few selected countries are compared in this study. From the comparison it is remarkable that although the two concepts, i.e. gap acceptance on the minor road and stopping on the major road have different backgrounds, but their outcome in terms of required sight distances are similar. Both distances are depending on speed on the major road: gap sight distances show a linear, while stopping sight distances a parabolic function. In general, European SSD values are quite similar to each other. However, the US and Australian guidelines based on gap acceptance criteria recommend higher sight distances. Human capabilities and limitations are considered in sight field requirements. Autonomous vehicles survey their environment with sensors which are different from the human vision in terms of identifying objects, estimating distances or speeds of other vehicles. This paper compares current sight field requirements based on conventional vehicles and those required for autonomous vehicles. Visibility requirements were defined by three vision indicators: distance, angle of view and resolution abilities of autonomous cars and human drivers. These indicators were calculated separately for autonomous vehicles and human drivers for various speeds on the main road and for intersections with 90° and 60° angles. It was shown that the required sight distances are 10 to 40 meters shorter for autonomous vehicles than for conventional ones.

We tested the hypothesis that road safety improves at junctions between minor roads and major roads if the minor roads are modally filtered to remove through traffic. We did this by using police-reported casualty data (2012–2024) to examine the effects of 113 Low Traffic Neighbourhoods (LTNs) implemented in London between 2015 and 2024. Our findings supported our hypothesis: LTN implementation was associated with a 14% reduction in total numbers of casualties at junctions between newly filtered minor roads and surrounding major roads (95% CI: -21% to -8%). This effect was generally consistent across casualty injury severity, casualty travel mode, and the presence of traffic-light controlled signals.

BackgroundMost analysis of road injuries examines the risk experienced by people using different modes of transport, for instance, pedestrian fatalities per-head or per-km. A small but growing field analyses the...

Accurately estimating annual average daily traffic (AADT) on minor roads is essential for assessing traffic-related air pollution (TRAP) exposure, particularly in areas where most people live. Our study assessed the direct and indirect external validity of three methods used to estimate AADT on minor roads in Melbourne, Australia.We estimated the minor road AADT using a fixed-value approach (assuming 600 vehicles/day) and linear and negative binomial (NB) models. The models were generated using road type, road importance index, AADT and distance of the nearest major road, population density, workplace density, and weighted road density. External measurements of traffic counts, as well as black carbon (BC) and ultrafine particles (UFP), were conducted at 201 sites for direct and indirect validation, respectively. Statistical tests included Akaike information criterion (AIC) to compare models' performance, the concordance correlation coefficient (CCC) for direct validation, and Spearman's correlation coefficient for indirect validation. Results show that 88.5% of the roads in Melbourne are minor, yet only 18.9% have AADT. The performance assessment of minor road models indicated comparable performance for both models (AIC of 1,023,686 vs. 1,058,502). In the direct validation with external traffic measurements, there was no difference between the three methods for overall minor roads. However, for minor roads within residential areas, CCC (95% confidence interval [CI]) values were −0.001 (−0.17; 0.18), 0.47 (0.32; 0.60), and 0.29 (0.18; 0.39) for the fixed-value approach, the linear model, and the NB model, respectively. In the indirect validation, we found differences only on UFP where the Spearman's correlation (95% CI) for both models and fixed-value approach were 0.50 (0.37; 0.62) and 0.34 (0.19; 0.48), respectively. In conclusion, our linear model outperformed the fixed-value approach when compared against traffic and TRAP measurements. The methodology followed in this study is relevant to locations with incomplete minor road AADT data.

This paper deals with the analysis of two classes of batch arrivals, one is high priority and other is low priority(retrial) customers with non-preemptive priority service, working vacations, negative arrival, emergency vacation for an unreliable server, which consists of a break-down by negative arrival and delay time to start repair. When there are no customers in the queue and in the orbit at the time of service completion for a positive customers, the server goes for a working vacation. The server works at a lower service rate during working vacation period. If there are no customers in the system at the end of vacation, the server becomes idle and ready for serving the new arrivals with probability p(single working vacation) or it remains on vacation with probability $$q=(1{-}p)$$ (multiple working vacations). Here we assume that customers arrive according to compound Poisson process in which high priority customers are assigned to class one and class two customers are of a low priority type. The priority customers that find the server busy are queued and then served in accordance with FCFS discipline. The arriving low priority customers on finding the server busy are queued in the orbit in accordance with FCFS constant retrial policy. The arrival of negative customer remove the customer being in service and makes the server breakdown and the server fail for a short interval of time. When the server fails it will send to repair. But the repair time do not start immediately, there is a delay time to start the repair process. We consider an emergency vacation which means that during the service time the server suddenly go for a vacation and the interrupted customer waits to getting the remaining service. The retrial time, service time, emergency vacation time, delay time and repair time are all follows general(arbitrary) distribution, working vacation time and negative arrival follows exponential distribution. The time dependent probability generating functions have been obtained in terms of their Laplace transforms and the corresponding steady state results are obtained explicitly. Also some performance measures of our model such as the system state probabilities, reliability indices, the average number of customer in the high priority queue and the low priority in the orbit and the average waiting time are derived. Numerical results are computed and graphical representations are presented.

본 연구에서는 지방부 간선 또는 지선 축에서 효과적으로 사용 가능한 연동형 반감응 신호제어 알고리즘을 개발하고 이를 평가하였다. 연동형 반감응 신호제어에 대한 모의실험 결과를 살펴보면, 주 부 도로의 교통량 차이가 커질수록 연동형 반감응 신호제어의 지체가 최적화된 고정식 신호제어에 비해 감소하는 것을 확인하였다. 그러나 주부도로의 교통량이 같거나 전체 교통량이 많아지면 최적화된 고정식 신호제어의 지체가 더 낮게 나타났으며, 횡단 보행량이 많아질수록 차량 지체가 증가하는 것으로 확인되었다. 따라서 연동형 반감응 신호제어는 차량 교통량이 일정수준 이하인 곳에 적용하되, 횡단 보행량을 고려하여 적용지역을 선별해야 할 것이다. In this paper, Coordinated Semi-Actuated Signal Control algorithm was developed and evaluated. According to the analysis of simulation, the coordinated semi-actuated signal control led to reduced vehicle delay as the difference of traffic volume between major and minor streets was getting bigger. But when there was relatively high traffic volume, or the equivalent amount of traffic volume on major and minor streets, optimized pre-timed signal control was verified to lower delay times compared to coordinated semi-actuated signal control; however, it might increase pedestrian delay. Therefore, the coordinated semi-actuated signal control should be implemented at intersections where traffic volume is relatively low.

Investigating the impacts of crash prediction models on quantifying safety effectiveness of Adaptive Signal Control Systems

This study intends to build a traffic accident predictive model considering road geometrics, traffic and enviromental characteristics and identify the relationship of 4-legs intersection accidents in Seoul and Busan metropolitan area. The RPNB(Random Parameter Negative Binomial) model shows improvement over the fixed NB(Negative Binomial) and out of 53 variables, 10 variables (main road number of lane, main road vehicle traffic volume(left), minor road vehicle traffic volume(right), main road drive restriction, minor road sight distance, minor road median strip, minor road speed limit, minor road speed restriction) showed to have significant variables affecting traffic accident occurrences in 4-legs signilized intersections. Also, among 10 significant variables, 2 variables(minor road sight distance, minor road speed restriction) found to be random parameters.

The critical gap/lag value for an uncontrolled intersection is an important parameter in estimating highway traffic capacity and developing micro stimulations of traffic movements. In manoeuvring an intersection, drivers decide to accept or reject the gap, based on several considerations. However, only a few studies have been carried out to estimate the critical gap on Sri Lankan roads; meanwhile, estimates of external factors are rare. This study found the influence of external factors on drivers’ gap acceptance decision and estimated the critical gap/ lag values using the Binary Logistic model. Analysis considered 4,233 gap acceptance decisions taken by drivers on minor roads. These were collected at three four-way and two three-way intersections and analysed across three vehicle categories: Motorcycle, Threewheeler, and Car/Van. Among the external factors studied, vehicle type, intersection type, size of the available gap, and type of traffic manoeuvre were found to have a significant influence on gap acceptance. Critical gap/lag values found in this study can be used for capacity estimation of three-way and four-way intersections in Sri Lanka.

Effectiveness evaluation of water-sprinkling in controlling urban fugitive road dust based on TRAKER method: A case study in Baoding, China