Gap Acceptance Behavior Of Drivers Research Articles

ORGANIZATION OF TRAFFIC AT UNCONTROLLED INTERSECTIONS

This paper presents a study of drivers' gap acceptance behavior at an uncontrolled intersection. A 4-leg uncontrolled intersection located in a semi-urban area of Ahmedabad, Gujarat was selected to study the gap acceptance behavior of drivers. Video recording technique was adopted for data collection and analysis. Various available methods are used to calculate the critical gap for minor road passing and right turn movements. Gaps are analyzed for three different vehicle types. A comparison is made between the various existing methods of critical gap detection and their critical analysis is presented. The result shows that except for the behavior elimination approach, all other methods cannot provide the real scenario of the critical gap under mixed traffic conditions because all these methods are developed for homogeneous traffic conditions.

Gap acceptance behavior of drivers at uncontrolled T-intersections under mixed traffic conditions

Explicit traffic control measures are absent in uncontrolled intersections which make them susceptible to frequent conflicts and resulting collisions between vehicles. In developing countries like India, drivers at such intersections do not yield to higher priority movements which cause more crashes between vehicles. The objective of this study is to analyze and model the gap acceptance behavior of minor street drivers at uncontrolled T-intersections considering their aggressive nature. Three intersections in the northeast region of India have been selected as the case study area. Preliminary analysis of the data revealed that drivers behave aggressively, not because they have to wait for a long time at the stop line, but because of their lack of respect for traffic rules. Binary logit models are developed for minor road right turning vehicles which show that gap acceptance behavior is influenced by gap duration, clearing time and aggressive nature of drivers. The equations obtained were used to estimate the critical gaps for aggressive and non-aggressive drivers. Critical gaps are also calculated using an existing method called clearing behavior approach. It is also shown that the estimation of critical gap is more realistic if clearing time and aggressive behavior of drivers are considered.

Modified INAFOGA method for critical gap estimation at u-turn median openings

The gap acceptance behavior of drivers at U-turn median openings is studied by considering the critical gap which cannot be obtained directly by field measurements. A thorough investigation on critical gap estimation is carried out by collecting the data sets from median openings at 4-, 6-, and 8-lane roads of Hyderabad City, India. Wide difference (10–42%) among the critical gap values estimated by the application of existing methods shows the limitation to consider for the mixed traffic situations. To address this issue, recently developed method Influence Area for Gap Acceptance (INAFOGA) which is based on clearing behavior of drivers at unsignalised intersections is modified and applied considering the merging behaviour of U-turn vehicles at median openings and named ‘Modified INAFOGA’ method. Modified INAFOGA method is compared with probability equilibrium method through paired-sample hypothesis (t test), and result revealed that difference in mean values 0.009 signifies that both methods are comparable. Difference in critical gap values obtained from the box plots and radar charts indicates that probability equilibrium method is not suitable to address the behavior of U-turn vehicles at median openings under mixed traffic conditions. These observations coupled with higher critical gap values validate the fact that ‘modified INAFOGA’ method is indeed appropriate under mixed traffic conditions.

Computing the Minimal U-Turn Offset for an Unsignalized Superstreet

Despite the extensive implementations of unsignalized superstreets in practice, reliable methodologies for their geometric design remain unavailable. In recognition of the critical role of the U-turn offset length design, this study proposed an applicable tool to help traffic professionals determine the minimum required offset length for safety needs. The proposed model offers a convenient tool to evaluate a candidate design on the basis of traffic dynamics and driver gap acceptance behavior. In addition, this model can be used to assess whether installation of signals is needed to accommodate growing traffic. With the use of the surrogate safety assessment model as an unbiased tool, this study evaluated the safety performance of one superstreet with varied U-turn offset lengths (i.e., 700, 1,100, and 1,500 ft). Comparisons of the results of different designs indicated that the safety performance of the superstreet would not be compromised if the U-turn offset was reduced from 1,500 to 1,100 ft. However, more severe crashes were observed when the U-turn offset length was 700 ft. Further extensive analyses on different levels of demand also confirmed the need to properly design the offset length in an unsignalized superstreet.

Safety effectiveness of pavement design treatment at intersections: Left turning vehicles and pedestrians on crosswalks

Pedestrians are the most vulnerable road users as they are more exposed than other road users. Pedestrian safety at road intersections still remains the most vital and yet unsolved issue. One of the critical points in pedestrian safety is the occurrence of accidents between left-turning vehicle and pedestrians on crosswalks at signalized intersections. A crosswalk is a place designated for pedestrians and cyclists to cross vehicular roads safely. Drivers are expected to give priority to pedestrians or cyclists during interactions between them on the crosswalk. If a driver exhibits non-yielding behavior, the interaction will turn into a collision. This study examined the safety effect of three crosswalks designed with different materials such as red-colored material or brick pavement based on a safety performance study. The safety performance study considered left-turning driver's gap acceptance behavior and the severity of traffic conflict events between left-turning vehicles and pedestrians. The results of the study indicates that using brick pavement on a crosswalk increases the safety level of the crosswalk. Drivers at such crosswalks are more acquiescent to the priority rule.

An inclusive framework for automatic safety evaluation of roundabouts

ABSTRACTThis article presents an approach for studying different aspects of traffic safety at roundabouts. An automated safety analysis framework is used to detect different types of traffic conflicts, as well as the inappropriate negotiations and the gap acceptance behavior of drivers. To test the validity of the proposed method, a case study is used for a roundabout in Doha, Qatar. Seven types of traffic conflicts are studied and their severity is identified using the time-to-collision conflict indicator. Four common types of driver inappropriate negotiations behavior are also investigated. The analysis shows that most of the inappropriate negotiations and traffic conflicts are due to drivers' poor lane discipline that can be partially attributed to the poor lane marking. Gap acceptance behavior is also studied by identifying lead, lag, and total gaps. The traffic conflicts, inappropriate negotiations, and gap acceptance results are validated by a comparison with manual observations. The results of the validation process show the viability of the automated approach that produces acceptable results with less time and effort. Moreover, the data collected using this approach provides further insights on roundabout safety evaluation and has the potential for use in the assessment of roundabout design.

A review of critical gap estimation approaches at uncontrolled intersection in case of heterogeneous traffic conditions

The gap acceptance study is an indispensable study in the determination of capacity and delay of the individual moment at uncontrolled intersection and critical gap is one of the chief parameter allied with this study. Most of the studies related to critical gap estimation have been carried out in developed countries where traffic is homogeneous and rules of priorities as well as lane disciplines are voluntarily followed. However, in India, priority rules are less honored which consequently create more clashes on intersections and modelling of such behavior becomes complex. Even though very limited studies have been reported in such case. This paper presents the study of gap acceptance behavior of drivers on an uncontrolled intersection. In order to examine the gap acceptance behavior of drivers, 4-legged uncontrolled intersection located in a semi-urban area of Ahmedabad in the state of Gujarat was selected. Video recording technique was adopted for collection and analysis of the data. Different existing methods are used to calculate the critical gap for through and right turning movements from the minor road. Gaps are analyzed for three different vehicle types. A comparison between different existing methods of critical gap determination is carried out and their critical analysis is presented. The result shows, except clearing behavior approach, all other methods are failing to represent the actual scenario of the critical gap under mixed traffic conditions as these all methods had been developed for homogeneous traffic conditions.

Evaluation of left-turn lane offset using the naturalistic driving study data

IntroductionThe Strategic Highway Research Program 2 (SHRP 2) Naturalistic Driving Study (NDS) data were used to evaluate gap acceptance behavior of drivers at left-turn lanes with negative, zero, or positive offsets ranging from −29ft to +6ft. The objectives of the study were to develop guidance for the design of offset left-turn lanes used as a safety countermeasure, and to provide insight regarding the use of the NDS data to future users. MethodThe study included 3350 gaps in opposing traffic evaluated by 145 NDS volunteer drivers and 275 non-NDS drivers at 14 two-way stop-controlled intersections and 44 signalized opposing left-turn pairs. Logistic regression was used to model the critical gap length for drivers as a function of offset, under conditions when their view was either blocked or not by an opposing left-turning driver. ResultsThe analysis found that the critical gap was longer at left-turn lanes with negative offsets than at those with zero or positive offsets, and was also longer when sight distance was blocked by an opposing left-turning vehicle. Sight distance was much more likely to be restricted by an opposing left-turning vehicle at negative-offset and drivers at those intersections were less likely to accept a gap when an opposing left-turn driver was present. ConclusionsLonger gap lengths could potentially result in decreased operational efficiency of an intersection. In addition, drivers making left-turns at negative-offset left-turn lanes are, on average, more likely to leave the shortest amount of time between their turn and the arrival of the next opposing through-vehicle, which may present a potential safety concern. Practical applicationsThe findings provide guidance for highway designers considering using offset left-turn lanes as a crash countermeasure. This research also highlights the benefits and limitations of using the SHRP 2 NDS data to answer similar research questions.

GAP ACCEPTANCE FOR LEFT TURNS FROM THE MAJOR ROAD AT UNSIGNALIZED INTERSECTIONS

This paper attempts to identify factors that may influence the gap acceptance behavior of drivers who turn left from the major road at unsignalized intersections. Drivers’ accepted and rejected gaps as well as their age and gender were collected at six unsignalized intersections with both two and four lanes on the major road, with and without the presence of a Left-Turn Lane (LTL), and with both high and low Speed Limits (SLs). Whether or not a driver accepts a given gap was considered as a binary decision and correlated logit models were used to estimate the probability of accepting a gap. Models with different factors were tested and the best model was selected by the quasi-likelihood information criterion. The gap duration, the number of rejected gaps, the mean and total time interval of the rejected gaps and the gender of the driver were all significant in explaining the variation of the gap acceptance probability, whereas the number of lanes of the major road, the presence of LTL, the SL and the driver’s age category were not. Gap acceptance probability functions were determined based on the best model, including both the factors of the number of rejected gaps and the mean time interval of the rejected gaps. As the values of these two factors increase, the probability of accepting a given gap rises up. The developed model can be further applied in practice to improve the analysis of traffic operations and capacity at unsignalized intersections.

Probabilistic Design of Freeway Entrance Speed-Change Lanes considering Acceleration and Gap Acceptance Behavior

An adequate length of entrance speed-change lanes (SCLs) is required for vehicles’ acceleration and gap-searching purposes so that vehicles can merge onto the freeway comfortably. The current design guides use a deterministic approach for the design of SCL length based only on the acceleration behavior of vehicles in the SCL. This study introduces a probabilistic approach for the design of the length of SCLs that considers both acceleration and gap acceptance behavior of drivers during the merging process. A microscopic simulation, coupled with a Monte Carlo simulation technique, is used to develop a probabilistic model to evaluate the probability of a forced merge by vehicles in the SCL, termed the probability of noncompliance (PNC). Reliability measures can be developed on the basis of the distribution of PNC values for all simulated SCL vehicles at a specific site. Several such measures are estimated for seven study sites and are shown to have high potential to indicate the safety performance at entrance SCL sites. As an example application of the developed model, the mean PNC is estimated to the SCL lengths recommended in North American design guides for a specific freeway design speed but different values of controlling curve design speed and traffic volume in the freeway right lane. The results indicate that the mean PNC may change with the change of either the design speed of the ramp controlling curve or the traffic volume on the freeway right lane.

Spatial and Temporal Analysis of Driver Gap Acceptance Behavior at Modern Roundabouts

Despite an increasing acceptance of modern roundabouts in the United States, unfamiliarity with this type of intersection is still widespread. This unfamiliarity results in drivers making unpredictable decisions about gap acceptance, thus increasing the difficulty of design decisions. The relationship between the spatial and temporal critical gaps accepted by drivers in modern roundabouts is explored with gap acceptance data from more than 1,500 vehicle interactions at the roundabout on the University of Massachusetts, Amherst, campus. The critical gap was determined to be 42 ft spatially and 2.2 s temporally, which correlated directly with the average speed of the circulating flow. A longer critical gap time was observed for heavy vehicles in the traffic stream. Even though the unidirectional flow of the circulating traffic creates a potentially unpredictable environment for the driver, careful and precise analysis to obtain an accurate and reliable value of the critical gap will allow for improved roundabout design.

Agent-Based Framework for Modeling Gap Acceptance Behavior of Drivers Turning Left at Signalized Intersections

An algorithm based on a reactive driving agent was developed for modeling gap acceptance behavior of drivers making left turns at signalized intersections. The model considers the interaction between driver characteristics and the physical capabilities of vehicles. A vehicle dynamics model explicitly captures the vehicle constraints on driving behavior. In addition, the model uses the driver's input and psychological deliberation about accepting or rejecting a gap. The model was developed with a total of 301 accepted gaps and validated with 2,429 rejected gaps at the same site and with 1,485 gap decisions (323 accepted and 1,162 rejected) at another site. The proposed model is a mix of traditional and reactive methods for decision making and consists of three main components: input, data processing, and output. The input component uses sensing information and vehicle and driver characteristics to process the data and estimate the critical gap value. Then, the agent decides to either accept or reject the offered gap by comparing it to a driver-specific critical gap. (The offered gap should be greater than the critical gap for it to be accepted.) The results demonstrate that the agent-based model is superior to the standard logistic regression model because it produces consistent performance for accepted and rejected gaps (correct predictions in 90% of the observations), and the model is easily transferable to different sites. The proposed modeling framework can be generalized to capture vehicle types, roadway configurations, traffic movements, intersection characteristics, and weather effects on driver gap acceptance behavior. The findings could be used to develop weather-specific traffic signal timing and in vehicle-to-vehicle communications.

Impact of Inclement Weather on Left-Turn Gap Acceptance Behavior of Drivers

This paper describes an empirical study conducted to quantify the impact of a number of variables on left-turn gap acceptance behavior of drivers at signalized intersections. The variables include the gap duration, the travel time needed to cross the intersection, and the corresponding weather condition. The gap acceptance data set used in the study included 11,114 observations (1,176 accepted gaps and 9,938 rejected gaps) for a permitted left-turn maneuver at a signalized intersection; the data were gathered over 6 months. The data set was divided into six weather categories for different combinations of precipitation and roadway surface conditions. Logistic regression models were calibrated to the data and compared to identify the best model for capturing gap acceptance behavior of drivers. The models reveal that drivers are more conservative during snow than rain. Drivers require larger gaps for wet surface conditions than for snowy and icy surface conditions, and drivers require the smallest gaps for dry roadway conditions. In addition, the models show that drivers require larger gaps as the distance required to traverse the offered gap increases. The study also shows how inclement weather and the number of opposing lanes affect permitted left-turn saturation flow rates. It is anticipated that these findings will be used to develop weather-specific traffic signal timings that account for changes in traffic stream saturation flow rates and also used for intelligent assistance systems for drivers.

Influence of Restricted Sight Distances on Permitted Left-Turn Operation at Signalized Intersections

Adequate sight distance is an important factor needed to provide safe and efficient operation of left-turn movements at signalized intersections. This factor becomes more crucial for left turners attempting this maneuver during the permitted phase of the traffic signal. The large size median of the major road is commonly designed to accommodate an exclusive left-turn lane. However, studies have proved that if the median of that major road is relatively wide, the simultaneously turning vehicles in the opposite left-turn lanes often restrict driver's sight distances for each other. In this study, a field observation was conducted to analyze the changes of left-turn gap acceptance parameters associated with drivers' restricted sight distances. Theoretical models were developed and used to quantify the negative effect of the restricted sight problem on the left-turn capacity. The results show that the sight-distance problem may contribute to significant increments of the critical gap and follow-up time. This influence on driver's gap-acceptance behavior may result in a 70% reduction in the left-turn capacity when the opposing-through traffic volume increases up to 1,800 vehicles/h. The capacity reduction rate increases with the increase in both the opposing-through traffic volume and the volume-to-capacity ratio of the opposing left-turn traffic.

Study of Driver Gap Acceptance Behavior at Merging Area in Baghdad City

This paper describes a traffic behavior at merging (on-ramp) area in Baghdad city. The objective is to predict the acceptable and critical gap necessary for completing merging process in an on-ramp area for vehicles to enter the highway based on observed traffic data.Data were collected from two selected sites which had certain characteristics both operational and geometrical to fit the criteria needed for gap acceptance study which were presented hereinafter. These two sites were on-ramp sections at Mohamed Al-Qasim highway and the Army-Canal highway.Video-recording equipments were used to collect data. The observed data were analyzed, grouped, and processed using computer programs developed by the researcher for this purpose. Standard statistical analysis techniques were used to examine and analyze the observed data.Gap acceptance results are used to determine the critical gap. Critical gaps are playing main role to evaluate level of service and capacity at Highway merging sections. This study measures gaps in the major stream regarding to driver behavior for traffic stream in the merging area. It has been found that different types of drivers will accept different gaps, more aggressive drivers will accept smaller gaps and conservative drivers accept larger gaps.Keywords / Traffic behavior, Gap acceptance, Critical gap, Merging area, Highway capacity.

Comparison of Capacity Models for Two-Lane Roundabouts

Multilane roundabout capacity models are presented and contrasted in the context of a case study. A two-lane roundabout in Copenhagen, Denmark, was investigated, and data were collected that enable the estimation of critical gaps, follow-on times, entry capacity, and delay. The primary objective of this research was to evaluate the need for more complex capacity models than currently exist in order to properly represent driver gap-acceptance behavior at multilane roundabouts. The complexity arises when drivers are assumed to simultaneously accept pairs of critical gaps in the outer and inner circulating lanes before they enter the roundabout. This approach requires that circulating-lane headways and critical gaps be evaluated independently and not be superposed in a single traffic stream as most current capacity guides assume. The approach also implies that circulating-lane volume allocation can have a considerable impact on entry capacity. The field results indicated that indeed there were differences in the gap-acceptance behavior for drivers entering in the right approach lane, with critical gaps estimated at 3.68 s and 4.49 s for the inner and outer circulating lane, respectively, at the test site. In contrast, drivers entering in the left approach lane exhibited no difference in critical gaps among lanes (4.64 s for the inner lane and 4.68 s for the outer lane). Finally, the lane allocation of circulating flow did have a significant impact on capacity, particularly at large circulating-flow rates. This finding implies that the origin and destination of the flow constituting the circulating traffic must be accounted for in estimating capacity. Even small errors in capacity estimation were found to have a significant impact on delay and level of service.

A decision model for gap acceptance and capacity at intersections

The purpose of this paper is to present a microscopic decision model for driver gap-acceptance behavior when waiting at an unsignalized intersection on the secondary road and also to estimate the resulting intersection capacity. The model is based on evaluation of the risk associated with not accepting small gaps against the potential benefit of their acceptance, which is the time saved as a result of shorter waits at the entry line. The model takes into account individual preferences by defining individual critical gap, which is different from the traditional macroscopic critical-gap approach. The latter estimates the critical gap for the entire population of drivers. The paper presents the difference between different driver populations (risk-loving vs. cautious) and shows how this difference actually results in different capacities on the minor road.

Capacity and performance of roundabouts

Empirical and theoretical approaches for assessing the capacity and performance of roundabout entries have provided inconsistent results. It was believed that an efficient modeling of gap-acceptance behavior of drivers entering into a roundabout would provide more insight for assessing roundabout operation. Accordingly, this study used logit modeling to predict the probability that a randomly selected driver will accept a given gap in the circulating traffic stream based upon roundabout and gap characteristics. Also, the study has developed move-up time models using both the roundabout geometry and circulating traffic characteristics. The developed gap-acceptance and move-up time models have implications in roundabout capacity estimation analysis. Finally, the results of the developed models are incorporated into the Australian and German gap theoretical models to judge the feasibility of using these theoretical models for Jordan conditions. Compared with an empirical data set, the Australian theoretical model with a minimum headway of 0.5 s provides reasonable results.Key words: capacity analysis, probabilistic approach, roundabouts.

Influence of Stopped Delay on Driver Gap Acceptance Behavior

A study is reported which estimates gap acceptance parameters for different groups of drivers who experienced varying durations of stopped delay and compares it with parameters estimated from aggregated data. The study statistically compared the mean critical gaps obtained from the disaggregated data with that obtained from the aggregated data. The investigation also speculated on the likely implications on the computed minor road capacity arising from differences in the estimated mean critical gaps for each duration of delay as compared with the value from aggregated data. The study results support the hypothesis that the duration of stopped delay experienced by minor road drivers while assessing gaps in the main traffic stream influences their gap acceptance behavior.