Two-way Stop Research Articles

Identifying the Adaptability of Different Control Types Based on Delay and Capacity for Isolated Intersection

In urban road networks, intersections are the main bottlenecks. Selecting an appropriate intersection control type can significantly improve the performance of an isolated intersection. Therefore, this paper offers recommendations for selecting the most efficient control type among two-way stop control, signalized intersection (SIG), roundabout (RB), and signalized roundabout (SIGRB) based on capacity and delay. The procedure to calculate delay and capacity is taken from the Highway Capacity Manual 6th edition (2016), or developed separately if needed. Two flow patterns are assumed: fixed and time-varying demand. For fixed demand, the results show that SIGRB outperforms other control types both in capacity and delay at higher demand levels. It was also observed that increase in left-turn ratio increases the delay and decreases the capacity of all control types while its impact on SIGRB was the least. Considering time-varying demand, traffic volume fluctuates over the 5-h period of the analysis. It was found that using both RB and SIGRB together creates significantly less delay compared with the other options. Additionally, using RB provides less variability in delay when there is fluctuation in demand. The major finding of this research is that RB and SIGRB have potential benefits for delay in conditions of (i) high traffic volume, (ii) high left-turn ratio, and (iii) demand fluctuation. Furthermore, it is suggested that SIG should be used if the left-turn ratio is relatively low. The results of this study could help decision-makers to choose the best control type for an isolated intersection under various traffic conditions.

Selection of Intersection Control Type in Urban Areas

Abstract In Egypt, urban planning projects usually do not consider the intersection type. This study developed charts for practitioners that could be used to determine the optimal intersection. The paper studied intersections including; signalized, roundabout, and two-way stop control. It provides a study for the intersection at the targeted level of service D. The traffic patterns were used to calculate the intersection’s capacity and the average control delay. The combinations of turning distribution, percent of heavy vehicles, and type of control were considered. The relationship among capacity, delay and traffic volume has been used to deduce the minimum required lane configuration for each intersection. The results indicated that the roundabout is the best alternative for intersection control with maximum capacity and minimum delays for medium traffic. However, signalized intersection is the best alternative at heavy traffic volumes and a high proportion of left-turning volume.

Impact of Intersection Control on Battery Electric Vehicle Energy Consumption

Battery electric vehicle (BEV) sales have significantly increased in recent years. They have different energy consumption patterns compared to the fuel consumption patterns of internal combustion engine vehicles (ICEVs). This study quantified the impact of intersection control approaches—roundabout, traffic signal, and two-way stop controls—on BEVs’ energy consumption. The paper systematically investigates BEVs’ energy consumption patterns compared to the fuel consumption of ICEVs. The results indicate that BEVs’ energy consumption patterns are significantly different than ICEVs’ patterns. For example, for BEVs approaching a high-speed intersection, the roundabout was found to be the most energy-efficient intersection control, while the two-way stop sign was the least efficient. In contrast, for ICEVs, the two-way stop sign was the most fuel-efficient control, while the roundabout was the least efficient. Findings also indicate that the energy saving of traffic signal coordination was less significant for BEVs compared to the fuel consumption of ICEVs since more regenerative energy is produced when partial or poorly coordinated signal plans are implemented. The study confirms that BEV regenerative energy is a major factor in energy efficiency, and that BEVs recover different amounts of energy in different urban driving environments. The study suggests that new transportation facilities and control strategies should be designed to enhance BEVs’ energy efficiency, particularly in zero emission zones.

Braking behavior of major approach turning vehicles at rural two-way stop controlled intersections: A naturalistic driving study

Objective: Using naturalistic driving data, this study analyzed the driving behavior of major approach right and left turning vehicles to minor approach at rural two-way stop controlled intersections by detecting the location where drivers reacted to the upcoming intersection to complete a turning maneuver.Methods: The study used 449 time series traces from 29 two-way stop controlled intersections across five states for the analysis. All 449 traces were associated to free flow condition with driving not obstructed by the vehicle ahead. Each time series trace was analyzed to check the point drivers first reacted to the intersection for the turning maneuver and this point was called the reaction point. Braking Behavior of Major Approach Turning Vehicles at Rural Two-Way Stop Controlled Intersections: A Naturalistic Driving StudyResults: The results from this study showed that right turning vehicles began reacting, in general, sooner than left turning vehicles. More than 75% of drivers showed a reaction within 300 meters upstream of intersection for both types of turning maneuver. The study found driving speed at the reaction point significantly affecting the initial point of reaction. Drivers who were traveling faster than the posted speed limit were associated with a reaction point farther upstream than vehicles traveling at the speed limit. On-pavement marking upstream of the intersection was found to be associated with longer reaction distance, while posted intersection ahead warning signs showed a reverse effect. The result provides information on braking zone of turning vehicles at intersections which has implication on the placement of different countermeasures upstream at the major approach.Conclusions: By detecting reaction distance of all 449 time series trace, the study provides an influence area of the intersection for the turning vehicles.

The Research Into the Influence of Non-Resident Drivers on the Critical Headway and Follow-Up Headway at an Unsignalised Intersection

The input parameters in the procedure for calculating the minor movement capacity of the unsignalised intersection are the values of conflict flow, critical haedway and follow-up headway. The conflict flow value is established in exact measuring, on the basis of flow values on approaches and their distribution by driving directions. On the other hand, the values of the critical headway and the follow-up headway are the parameters which depend on the estimate and the behaviour of the drivers doing the minor movement. On account of that, these parameter values depend on different factors and influences, therefore, they are not identical at all intersections. In the procedures for calculating the capacity of two-way stop controlled inersections, the values of critical headway and follow-up headway are given as recommendations. Some of the methods for capacity calculations, such as Highway Capacity Manual, recommend the research on these parameter values in local conditions, considering different influences. This paper presents the results of the research into the influence of non-resident drivers on the features and values of critical headway and follow-up headway, and thereby on the intersection capacity as well.

Warrants for roundabouts and other traffic control devices

There are many warrants for traffic signals, but no definitive warrant for roundabouts. Some references (e.g. TRB 2000) give guidelines, and refer to the capacities of roundabouts and TWSC (two-way stop control), but capacities address the upper limit of the control device, not the lower values which would justify, or warrant, a change in control. Other references refer to the need for a roundabout warrant but do not develop one. One paper by Sampson and Meijer (1999) discussed potential warrants, but no recommendation was made. In this paper the role of roundabouts and mini-circles in filling the large gap between where stop control is no longer ideal, and where traffic signals are required, is examined. It is found that there are many considerations in addition to volume or delay that need to be taken into account when deciding on whether to implement roundabout type control, but as a rule of thumb, if the average queue at a stop control exceeds two (2Q) during the peak hour, roundabouts will improve the traffic flow, and if the queue totals around ten or more (10Q), then the roundabout is likely to have reached its capacity.

Analyzing variations in spatial critical gaps at two-way stop controlled intersections using parametric and non-parametric techniques

At two-way stop controlled (TWSC) intersections drivers on minor stream are generally at risk because of the difficulty in judging safe gap between major stream vehicles. Any misjudgment by the driver while choosing gap may result in a collision with major stream vehicle. This paper provides important insights for determining and analyzing spatial critical gaps of drivers at high speed and medium speed TWSC intersections. The critical gap line (CGL) fitted for the accepted and rejected gaps using parametric (binary logit model-BLM) and non-parametric (support vector machines-SVM) techniques gives critical gap values at 15th, 50th and 85th percentile speeds. The evaluation of spatial critical gap with respect to major road vehicle (conflicting vehicle) speed makes it easier to understand the impact of variation in speed on spatial gaps accepted by the drivers on the minor road. The logit models developed revealed that the probability of accepting gap decreases with increase in the speed of the conflicting vehicle and it increases with increase in the distance of conflicting vehicle. The spatial critical gaps estimated using support vector machines were found in close approximation with those estimated using binary logit model. The study results showed that SVMs have very good potential to be an alternative tool for the estimation of driver's critical gap. The spatial critical gaps corresponding to 15th, 50th and 85th percentile speeds for medium speed intersections were 32 m, 38 m and 46 m respectively and for high speed intersections these values were 64 m, 76 m and 104 m respectively. The increase in the magnitude of gap value with respect to the percentile speed clearly states the effect of speed on spatial gaps. The insights from the study can be used to suggest various measures to improve the safety of crossing drivers at uncontrolled intersections. • The study provides important insights for analyzing spatial critical gaps at high speed and medium speed uncontrolled intersections. • BLM and SVM are used as a linear classifiers to fit decision boundary between accepted and rejected gaps. • The spatial critical gaps estimated using BLM and SVM corresponding to 85th percentile speed are 46 m and 45 m respectively. • SVMs have very good potential to be an alternative tool for the estimation of driver's critical gap.

Developing and Implementing Manual on Uniform Traffic Control Devices Criteria for Selecting Traffic Control for Unsignalized Intersections

The 2009 United States Manual on Uniform Traffic Control Devices (MUTCD) includes guidance for the use of various types of traffic control at unsignalized intersections. Despite changes and advances in traffic engineering in recent decades, the MUTCD content related to selection of traffic control in Part 2B has seen only minor changes since 1971. The types of unsignalized traffic control addressed in the current research included no control, yield control, two-way stop control, and all-way stop control. The research team developed recommendations using information available from reviews of existing literature, policies, guidelines, and findings from an economic analysis along with the engineering judgment of the research team and panel. The researchers then developed recommended language for the next edition of the MUTCD for unsignalized intersections. This includes consideration of high-speed (rural) and low-speed (urban) conditions along with the number of legs at the intersection. Because the number of expected crashes at an intersection is a function of the number of legs, the decision on appropriate traffic control should also be sensitive to the number of legs present. The proposed language includes introductory general considerations, discusses alternatives to changing right-of-way control, and steps through the various forms of unsignalized control from least restrictive to most restrictive, beginning with no control and concluding with all-way stop control.

Behavior of Drivers on Nonstandard Unsignalised Intersections

Nonstandard unsignalised intersections are two-way stop controlled intersection where two major approaches are not placed opposite, but next to each other. Driving priority on these intersections always is defined by additional traffic signs. This principle of regulation on intersection can be confusing for some drivers who, although they perform a turning maneuver do not include the direction indicator. The purpose of this research is the analysis of the driver’s behavior related to using of turning the signal during specified maneuver. Data collection was conducted using an online questionnaire and within the research in real traffic flow.

A comparative study on the operational performance of four-leg intersections by control type

The selection of proper control types at intersections at the planning stage is an important concern considering the difficulty in comparing the performance of different control types. Therefore, several manuals proposed selection charts to guide traffic engineers in identifying the control strategy that yields to the lowest delay and the highest level of service. However, most of these methodologies consider only total major and minor street traffic flows. They do not necessarily suggest to investigate the impact of turning traffic and pedestrian flows, which limits the applicability of their recommendations. Thus, this study aims to propose a procedure to assess the selection of the optimum control strategies among two-way stop, roundabout and signalization using average intersection vehicle delay as the evaluation criterion. The impact of turning traffic on the major and minor streets as well as the impact of pedestrians are integrated into the developed analytical methodology for the estimation of average intersection vehicle delay. A typical layout of isolated four-leg two-way intersection is assumed for the model development. It is concluded that turning traffic and pedestrians play essential roles in the performance of intersections. As pedestrian flow increases, signal control becomes prevailing over the other control types.

Effect of traffic roundabouts on accident rate and severity in Arizona

ABSTRACTAlthough roundabouts have been used at many locations around the world, the safety of roundabouts under different conditions has not been fully understood. In this study, 17 roundabouts in five cities in Arizona were evaluated, out of which 11 are single lane and six are double lane. Most of the intersections of single-lane roundabouts were controlled by two-way stop signs before roundabout conversion, whereas most of the intersections of double-lane roundabouts were controlled by traffic signals. Accident data were collected and broken down into five categories: damage without injury, minor injury, nonincapacitating injury, incapacitating injury, and fatality. Equal number of years were used before and after the roundabout conversion at each location. The average rates of accidents, damages without injury, injuries and fatalities per year and per million vehicles were evaluated. It was found that single-lane roundabouts reduced the accident rate, whereas double-lane roundabouts increased the accident rate. The results also showed that single- and double-lane roundabout conversions reduced the severity levels of accidents. Considering accident rate and severity level, warrants need to be developed for roundabout conversion and number of roundabout lanes under different traffic conditions.

Where do bike lanes work best? A Bayesian spatial model of bicycle lanes and bicycle crashes

US municipalities are increasingly introducing bicycle lanes to promote bicycle use, increase roadway safety and improve public health. The aim of this study was to identify specific locations where bicycle lanes, if created, could most effectively reduce crash rates. Previous research has found that bike lanes reduce crash incidence, but a lack of comprehensive bicycle traffic flow data has limited researchers’ ability to assess relationships at high spatial resolution. We used Bayesian conditional autoregressive logit models to relate the odds that a bicycle injury crash occurred on a street segment in Philadelphia, PA (n = 37,673) between 2011 and 2014 to characteristics of the street and adjacent intersections. Statistical models included interaction terms to address the problem of unknown bicycle traffic flows, and found bicycle lanes were associated with reduced crash odds of 48% in streets segments adjacent to 4-exit intersections, of 40% in streets with one- or two-way stop intersections, and of 43% in high traffic volume streets. Presence of bicycle lanes was not associated with change in crash odds at intersections with less or more than 4 exits, at 4-way stop and signalized intersections, on one-way streets and streets with trolley tracks, and on streets with low-moderate traffic volume. The effectiveness of bicycle lanes appears to depend most on the configuration of the adjacent intersections and on the volume of vehicular traffic. Our approach can be used to predict specific street segments on which the greatest absolute reduction in bicycle crash odds could occur by installing new bicycle lanes.

Capacity Analysis Procedure for Four-leg Non-standard Unsignalised Intersections

Procedures for capacity analysis of two-way stop controlled (TWSC) appeared in scientific literature in the 1970s. In addition to standard TWSC intersections, there are also non-standard unsignalised intersections. The main characteristic of these intersections is that two major approaches are not placed opposite, but next to each other. Because of the non-standard layout of the major and minor approaches, there are unique major and minor movements at these intersections. For these movements, standard procedures for capacity analysis of standard TWSC intersections cannot be used. This paper describes a procedure for capacity analysis of non-standard unsignalised intersections with a new model for rank distribution for all major and minor movements, as well as the conflict flow calculation, and the procedure for the calculation of potential and movement capacity, according to the non-standard layout of the major and minor approaches.

Speed Reduction Mitigation Strategies on Rural Highways at Two-Way Stop Control Intersections and Curves

Studies conducted on crashes at rural intersections of state highways and local roads/streets with two-way stop control have proved that the problem was likely poor judgment by the stopped driver on the minor approach of the speed of an oncoming vehicle and/or safe gap in traffic on the major highway. Several mitigating strategies have been suggested and studied in various studies to improve safety at the two-way stop control rural intersections and at other rural highway segments. There are also several low-cost techniques used, mostly in foreign countries, to slow drivers on major highways as they enter small towns and villages, e.g., narrowing pavement lines, establishing visual gateways, etc. Lowered speeds would decrease crash severity. In this study, four strategies including solar speed display units, mobile speed trailers, optical speed bars, and colored pavement were tested and assessed in some locations in Kansas. The results of this research indicate that both solar speed display units and mobile speed trailers are effective in speed reduction at the desired points, but optical speed bars and colored pavements do not yield reliable results. Additional studies and longer term studies, should be conducted.

Exploring environmentally sustainable traffic signal warrant for planning application

ABSTRACTWith the concerns over the greenhouse gas (GHG) emissions associated with the surface transportation, the environmentally sustainable traffic signal warrant is essential to provide guidelines for making environmentally conscious decisions about control types at intersections. This research conducted a pilot study on developing CO2 emissions-oriented traffic signal warrants. Intersection control types that were analyzed for this research include two-way stop, four-way stop, traffic signal, and roundabout. Two environmentally sustainable traffic signal warrants were proposed: Type I (without roundabout) and Type II (with roundabout). The proposed traffic signal warrants were compared with the existing mobility-oriented traffic signal warrant of the Manual on Uniform Traffic Control Devices (MUTCD) in terms of CO2 emissions and total delay. The measurements were collected and estimated using a microscopic traffic simulation tool, Verkehr In Stadten—SIMulationsmodell (VISSIM). The environmentally sustainable traffic signal warrants show that the annual CO2 emissions of the ground transportations in the USA were reduced by 7.2% with Type I warrant and 13.9% with Type II warrant.

Combining traffic efficiency and traffic safety in countermeasure selection to improve pedestrian safety at two-way stop controlled intersections

Decision makers are encouraged to consider multiple objectives (such as traffic efficiency, safety, and environment) together to make decisions. Although there are methods to evaluate each objective respectively, there are few reports or research papers showing how to incorporate these objectives and put it in practice. Thus, this study aims to develop a procedure to incorporate traffic efficiency into the traffic safety countermeasure (CM) selection process. To illustrate the procedure, the economic benefits of four pedestrian safety improvements at crosswalks of major-streets at two-way stop controlled intersections (TWSC) were calculated, considering not only the safety benefits but also the efficiency impacts. First, for each countermeasure the efficiency impacts were calculated as the average delay reduction for both pedestrians and motorists. Sensitivity analysis was conducted to examine how the crucial parameters, including vehicular volume, pedestrian volume, and motorist yield rate, offset the average vehicle and pedestrian delay. Next, the safety impacts were calculated as the crash reduction benefits for different CMs using safety performance functions (SPFs) and crash modification factors (CMFs). Finally, the equivalent uniform annual return (EUAR) method was used to combine the countervailing effects of efficiency and safety by evaluating the economic effectiveness of different CMs. The Monte Carlo (MC) simulation method was used to conduct uncertainty analysis by using random sampling from probability descriptions of uncertain input variables to generate a probabilistic description of results. The findings showed that, first, CMs can have tradeoff impacts for pedestrians and motorists. Second, the efficiency impacts accounted for a large proportion of the total impacts, which can significantly affect the selection of CMs. Third, the rankings of the CMs differ depending on whether the safety impacts alone are considered, or whether both safety and efficiency impacts are integrated. The study illustrates the detailed process of evaluating projects considering multiple objectives for multiple road users. This process offers policy and decision makers a solid and practical reference using existing guidebooks. The findings also explain how safety and efficiency objectives can countervail with each other in improving pedestrian safety at TWSC.

Time-of-day Visibility-based Pedestrian Gap Acceptance Model for Two-Way Stop Controlled Crossings

Conventional traffic engineering studies at two-way stop controlled (TWSC) pedestrian crossing locations have been largely interested in estimation of capacity and delay impacts due to pedestrian impedance. Review of the literature indicates that pedestrian gap acceptance behavior at TWSC locations has not been investigated in detail. The objective of this research was to obtain and use empirical observations from study sites in Alabama to develop pedestrian gap acceptance models at TWSC pedestrian crossings. Visibility due to daylight conditions was also explored. Discrete choice models with underlying normal and logistic distribution of error terms were developed. From the set of developed models, a probit model was found to be suitable for further empirical validation. Based on this model, gap length, presence of vehicle at minor street waiting for right of way, opportunity to cross the street in lag, and daylight visibility were found to affect pedestrian gap acceptance. This study broadens empirical pedestrian behavior model development to TWSC locations and is the first of its kind to elaborate on visibility impacts.

Investigation of surrogate measures for safety assessment of urban two-way stop controlled intersections

Crash prediction models used to estimate safety of highway segments and intersections are traditionally developed using various traffic volume measures. There are issues with this approach and surrogate safety measures such as conflicts and delays have been proposed to overcome them. This study investigates the statistical relationships between crash frequencies and traffic volume, intersection delay, and simulated conflicts to explore and compare the viability of these models for estimating safety at urban two-way stop controlled intersections. The database used includes 78 three leg and 55 four leg intersections within the city of Toronto, Canada. Crash prediction models were developed and evaluated based on various goodness-of-fit measures. With the developed models, an alternate approach to crash based evaluations of intersection improvements is presented. A case study is developed to investigate and demonstrate the use of the models for estimating the safety impact of implementing a left turn lane on...

An Estimate of Potential Savings From Removing Traffic Signals in a Depopulating Urban Area

A common rule of thumb for signalization in a city is one traffic signal for every 1,000 residents. When a city is depopulating, does this ratio apply when determining how many signals can be removed? The City of Detroit has lost 61% of its population since its peak. If signals were installed to serve the peak population, applying this rule of thumb, 61% of the signal inventory should be able to be removed. An operational analysis was performed on a random sample of the signal inventory of the City. Based on this sample, it was determined that 30% of the signal inventory could be removed and replaced with either two-way or all-way stop control, while still maintaining adequate levels-of-service for all approaches, resulting in a savings of US$460,000 to US$3,700,000 annually in operating costs. Other cities with declining populations should conduct similar analyses to reveal the extent of potential savings.

Safety and Economic Assessment of Converting Two-Way Stop-Controlled Intersections to Roundabouts on High Speed Rural Highways

This research addressed two questions: “Are roundabouts on rural high-speed roadways safer than two-way stop controlled (TWSC) intersections?” and “What economic benefits can be expected from converting TWSC intersections to roundabouts in terms of safety improvement?” Crash and traffic data on four TWSC intersections that were converted to roundabouts in Kansas were analyzed using the empirical Bayes before-after evaluation method and crash costs were applied to evaluate economic benefits. Analysis showed that fatal, non-fatal, and property-damage-only crashes were reduced by 100%, 76.47%, and 35.49%, respectively. The annual monetary value from this reduction was between $1.0—$1.6 million in 2014 dollars.