Implementing Actuated Signal-Controlled Intersection Capacity Analysis with Pedestrians

Transportation planning models do not usually consider intersection delays explicitly in calculating path travel times. However, because intersection delays often make up a considerable portion of total travel time in urban areas, ignoring them will result in inaccuracy in model results. Incorporating intersection delays into a traffic assignment model presents several challenges. One is that future signal timing plans are unknown, and another is that introducing intersection delays into traffic assignment renders the necessary condition for convergence invalid. This paper proposes a pragmatic approach to considering intersection delays in traffic assignment by assuming that signal timing plans will be optimized for given traffic conditions and by demonstrating that a convergent solution can be obtained when intersection delays are explicitly accounted for. A large data set of traffic volume combinations representing the operation of an intersection and the corresponding intersection delays based on optimized signal timing are obtained from TRANSYT-7F. This data set is used to train an artificial neural network (ANN) model that provides delay estimates for given traffic conditions for certain types of intersection configurations. An iterative process of traffic assignment and delay estimation is carried out to obtain a stable assignment solution. The delay estimates from the ANN delay model are evaluated by the percentage root mean squared errors, which are less than 25.6%, with larger prediction errors typically associated with severely oversaturated conditions. An example is presented to show the use of the delay model in traffic assignment. The delay model allows the concurrent optimization of signal controls and traffic routing to obtain a local optimum network solution.

Pedestrian crossings play an important role in the safety and mobility performance of signalized intersections. In improving pedestrian crossings, it is important to calculate the crossing speed. In practice, different average pedestrian crossing speeds can be effective in different pedestrian crossings. The differences in the design speeds also support the need to calculate local pedestrian crossing speeds in order to provide the most suitable designs. In the study, factors affecting pedestrian speeds at the selected signalized pedestrian crossing in Mersin city center were examined at a micro level. As a result of statistical analyses for the 1868 pedestrian crossing, the effects of gender, age, group behaviour, load condition in hand, telephone preoccupation, traffic and pedestrian volume on pedestrian crossing speeds were examined. The average crossing speed was calculated at 1.14 m/s. Individual situations affecting speed were found to be factors such as age, group behavior and having loads in hand. In addition, the actual subject studied was the signal effect, direction factor, and pedestrian-vehicle interaction factors studied by statistical methods and cumulative percentage pass rate graphs. Contrary to what is expected, pedestrians who exhibit angle crossing behavior with unregulated pedestrians have a lower crossing speed than canonical and normal passing pedestrians. In pedestrian crossing design, considering vehicle-pedestrian interaction while collecting data; It has been revealed by calculations that the cross and illegal crossings of pedestrians should be reduced and the width of the railings should be adjusted correctly. In addition, it is important to accurately determine the width of the crosswalk, which has an impact on the speed of the pedestrian.

The optimization of signal timing plans for isolated intersections is an extremely complicated procedure. Most current techniques such as the Canadian Capacity Guide for Signalized Intersections and the Highway Capacity Manual rely on relatively simple analytical models to estimate the optimum cycle time and green time splits, and leave the determination of the optimum phasing scheme to the experience of the user. The main problem with current procedures is that, due to the large amount of human effort that is required, only a very limited subset of all possible solutions can be examined. In addition, none of the current procedures are entirely satisfactory in their ability to deal with complicated congestion conditions. The interaction of shared lanes, permitted left turn movements, cycle times, and green time splits, requires an iterative approach to the design of signal timing plans, if current methods are to be used. Due to the large number of mathematical calculations that need be done, current procedures are, by and large, computerized. Using any of the procedures currently available, each time a further iteration is needed, a new set of saturation flow rates or volume allocations must be manually coded into the input files of the computerized procedure. Thus, the search for the optimum solution for a signal timing plan problem can require a large amount of engineering time. This paper describes the development of a notation and vocabulary that permits the automation of the logical decisions that must be made in order to optimize signal timing plan design. As well, the information that is necessary to define the intersection geometry and volume demands, in order that an automated process can optimize a signal timing plan, is presented. The rules that can be used to determine the phase of discharge of each lane and pedestrian demand volume, the lanes that are opposed by a conflicting movement, and the movements that oppose traffic attempting to discharge from a turning lane are also described. Finally, a brief description of the framework of SIGNAL EXPERT, a computer model that would automate all of the above, is provided.

Pedestrian crossings are important for accessing the adjacent land use facilities in daily life. Improperly designed crossing facilities cause discomfort to pedestrians and may even jeopardize their safety as well as being a hindrance to the smooth flow of vehicle traffic. These problems exist especially in developing countries such as India, where mixed traffic conditions prevail and road discipline is essentially absent. Thus, the design of efficient crossing facilities considering the flow of both pedestrians and vehicles is of utmost importance in these countries. In this regard, the objective of the current study was to propose warrants for pedestrian crossing facilities in midblock sections under mixed traffic conditions. To achieve this objective, pedestrian–vehicle ( PV2) conflict analysis was carried out at eight different unprotected midblock crosswalks in Mumbai, India. Videographic surveys were conducted and vehicle and pedestrian volumes were extracted, along with pedestrian-crossing characteristics such as crossing difficulty, safety and traffic, and vehicle characteristics. The initial computed PV2-values were adjusted by different factors, and k-means cluster analysis was carried out to determine the threshold PV2-values for selection of a suitable crosswalk facility. The study also highlighted the importance of taking into consideration site characteristics for evaluation of a midblock crosswalk facility. The results of this study are expected to have a wide range of applications in the design of new crosswalk facilities or in the improvement of existing pedestrian crosswalk facilities under mixed traffic conditions.

Every third road accident in Poland involves a pedestrian as a participant or, most of the time, a casualty. Pedestrian accidents are usually the result of complex situations and the outcome of a number of factors related to driver and pedestrian behaviour and road infrastructure. Safety depends largely on how well the traffic condition is perceived and on visibility in traffic. The paper presents the results of analyses of methodologies for systematic studies of pedestrian behaviour and pedestrian-driver relations. The effects of the location of the site, type of cross-section and other selected parameters on pedestrian and driver behaviour are demonstrated. The analyses showed that pedestrians are most often put at risk by too long pedestrian crossings, vehicles going too fast around pedestrian crossings, lack of proper sight distance and poorly lit or unlit pedestrian crossings. The reason for such defective infrastructure is that planners, designers, contractors and maintenance services are not receiving any support from design, marking and maintenance regulations for pedestrian traffic. In addition, the Road Traffic Law is not restrictive enough when it comes to drivers’ obligations towards pedestrian safety. Polish design regulations allow long pedestrian crossings up to four lanes in one direction or three lanes in two directions irrespective of traffic control and speed limits. Pedestrian crossings should be kept at a maximum of three lanes. There is nothing in the design regulations about the required driver-pedestrian sight distance. Neither does the Road Traffic Law help engineers with that. It is legal to park vehicles within 10 m of a pedestrian crossing which does not guarantee the necessary sight distance. Drivers must be able to see a pedestrian waiting or stepping onto the crossing from a distance that will help them come to a stop safely. It is safer to follow the principle of providing adequate pedestrian sight distance. Recommendations for pedestrian crossing design are also provided.

Although much is known about the operation of signalized intersections, little or no empirical research has been conducted regarding the effect of bicycles on signalized intersection capacity. The purpose of this study was to accurately quantify the effects of bicycles on signalized intersection capacity through the videotaping of several intersections that had significant bicycle traffic. Through the videotaping of intersections in Davis, California, and Gainesville, Florida, a relationship was determined between bicycle volumes and the percent of the green phase during which bicycle traffic occupies a conflict zone between bicycles and right-turning motor vehicles. It was also determined that one can ascertain the total net occupancy due to pedestrians and bicycles by taking the overlapping effects between bicycles and pedestrians into account. Using this total occupancy due to bicycles and pedestrians, one can calculate a saturation flow adjustment factor ( fRph) that reflects the reduction in saturation flow, and ultimately lane group capacity, for lane groups containing vehicles making permissive right turns in the presence of bicycles and pedestrians. The proposed procedure yields lower saturation flows and capacities than the current Highway Capacity Manual (HCM) procedure. In other words, on the basis of empirical data, when combined with pedestrian effects, the impact of bicycles on the saturation flow of lane groups containing right-turning vehicles is probably more detrimental than previously believed, and the capacities of intersections with significant bicycle and pedestrian traffic may be overestimated by using the current HCM procedures.

The main objective of the study was to verify the effectiveness of the active pedestrian crossings equipped with flashing lights activated automatically by detected pedestrians. Eight unsignalised pedestrian crossings were video-recorded for 48 hours each, both before and after installation of the equipment. An additional survey was done a month after the installation on three of the crossings. A traffic Conflict Rate was calculated for each crossing, as the number of conflicts per hour divided by the product of hourly pedestrian and vehicle traffic volume. The ANOVA test was used to check the statistical significance of changes of the indicators. The average percentage of drivers yielding to pedestrians increased by 94.8% and the average waiting time decreased by 39.2%. The Conflict Rate decreased at five out of eight sites. The average speeds of vehicles approaching the crossings decreased by 3.9 km/h. The “before-one month after” analysis mostly confirmed the positive results of the first analysis. Generally, at four out of eight crossings the effects were clearly positive, at two, relatively positive, and at the remaining two there was no clear positive effect. These sites were multilane streets which suggests that such sites should be either signalised or narrowed.

Signal timing optimization is one of the most important methods that improve the intersection serve level. The paper studies the signal optimization method that the phases have overlapped phase, the bi-level optimization method is used to solve the questions. Firstly, the critical phase is introduced in detail. Then the cycle optimization method TRRL and ARRB is described. Based on the cycle optimization method, the critical phase optimization method is given. Through an example, it is tested that intersection’s average delay is decreased by 21.37%, the average vehicle queue is decreased 10 pcu/c, the intersection capacity is increased 0.93% and the saturation of the intersection is reduce from 1.38 to 0.93. It is proved that the method given in this paper can make the signal time more effectively and the intersection has better serve level.

Weaving sections have been shown to have a great effect on capacity of a roundabout, because at weaving sections the traffic conflict and interference are predominant, resulting in a reduction of speed as well as increase of gaps. It is known that the weaving section of a roundabout is the bottleneck of the traffic movement. Therefore, it should be given the highest priority in the capacity analysis. The current methods of estimating the approach capacity of a roundabout mainly utilize information of vehicles entering and exiting the roundabout. From a literature review it has been found that few studies are conducted based on the traffic characteristics of a weaving section in capacity estimation. The purpose of this research is to estimate the capacity of a roundabout by modeling the radius of the roundabout, width of circulating roadway, and gap acceptance at the weaving sections. For this reason, a total of 21 roundabouts that are located at the metropolitan Beijing are selected to conduct data collection. Significance analysis of speed at weaving sections has been conducted by means of the variance analytic method. By taking geometric conditions and traffic conditions into account, new concepts of “Quasi-saturation state of roundabout” and “The Capacity of Roundabout” are introduced in this study. The regression models of the headway and the radius on both the outer lanes and the inner lanes are established respectively using Statistical Program for Social Sciences (SPSS 18.0) for Windows. Moreover, based on the theory of saturation flow rate, a new method is proposed to estimate the capacity of single-lane and multi-lane roundabouts using MATLAB software. And then the real data are taken to validate this model. The findings from this research demonstrate that capacity estimates with weaving section vehicles result in improved prediction of the actual capacity of a roundabout.

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.

Analysis of Downstream Queues on Upstream Capacity Expansion of Urban Signalized Intersection

This study investigates left-turn safety at urban intersections using surrogate safety measures derived from field video observations. Time-to-Collision (TTC) among motorized traffic and Post-Encroachment Time (PET) among pedestrian and motorized traffic were extracted for left-turn conflicts across five intersection types in Thessaloniki, Greece, and linked to geometric attributes, signal operations, and traffic conditions. Count-based models (Poisson, Negative Binomial) were estimated alongside machine-learning approaches (Random Forest, Gradient Boosting with Poisson loss). For PET events, the Poisson model had the best balance of parsimony and predictive accuracy, whereas the Negative Binomial model provided a superior fit for TTC events. Results indicate that PET-defined conflicts increased with pedestrian volume and the presence of shared and protected left-turn lanes, and decreased with higher opposing flow, greater average acceleration, and wider end-approach lanes. By contrast, TTC events were associated with lower average speeds, the presence of protected signal phasing for left turns, and the number of passenger cars. Machine-learning models underperformed relative to classical count models, reflecting limited sample size and the discrete event structure. The analysis indicates that the determinants of TTC and PET differ, with certain variables such as pedestrian activity and lane configuration having contrasting effects on the two surrogate safety measures. The analysis reveals that pedestrian demand and shared lane configurations significantly increase PET occurrences, whereas TTC events are more strongly associated with vehicle volumes, speeds, and signal phasing. This distinction underscores the importance of tailoring safety assessment and intervention strategies to the type of interaction being evaluated.

Comparative Study of Pedestrian Crossing Behaviour at Uncontrolled Intersection and Midblock Locations

Currently, in China, the single-objective optimization methods are commonly used for road intersection signal control, which has one single objective such as minimizing the number of stops, average delays, or queuing length. When the intersection traffic varies large with the time of day, using this method for intersection traffic control will always cause poor adaptability and low efficiency. To solve these problems, a multi-objective optimization method for signal control of single intersection is proposed, with the composite optimization objectives to minimize the average delay, the least number of stops, and the shortest vehicle queue length, which can set preferences of various optimization objectives to adapt to different traffic conditions. The method uses the Pareto multi-objective evolutionary algorithm to optimize signal timing parameters to get the best signal control plan. Simulation results show that this method can significantly improve the adaptability and efficiency of the intersection traffic control.

At present, a suitable methodology is not available for assessment of the quality of services offered by the transportation facilities like shared use roadway segments for pedestrian use under the influence of heterogeneous traffic flow. Hence an initiative has been taken in present study to develop a new method that can be well applicable for mid-sized cities. Required data sets has been collected from a total of 60 segments of three Indian cities namely; Bhubaneswar (Odisha), Rourkela (Odisha) and Kottayam (Kerala). These segments widely vary in their traffic flow and geometric conditions. Also, both kinds of segments, i.e. with and without provision of sidewalk facilities have been considered. The quality of walking environments offered by these segments has been examined. Approximately 700 respondents differing in their age, sex, education level and driving experiences participated in perception surveys to share their satisfaction level on these segments. Ten different variables affecting the service quality significantly (p < 0.001) has been found out and stepwise multi-variable regression analysis has been carried out to develop a new model. Primary factors included are namely: total available width of the road, paved shoulder and sidewalk facilities in through direction; volume of pedestrians and vehicles in peak hours of traffic flow; percentage of heavy vehicles; 85th percentile speed of running motor vehicles; and interruptions created by nearby commercial activities and available public transits. Also, influences of two secondary factors namely; availability of driveways and type of separation of sidewalk facilities from the main carriageway has been examined under prevailing conditions. These influences have been reflected in the developed model by using adjustment factors. This regression model reported high reliability in its universal application with a high correlation coefficient (R2) of = 0.75. Also, its parameter estimates satisfied required significance criteria through several tests including t test, collinearity statistics etc. Fuzzy C-Means clustering technique has been used to define the ranges of service categories (A–F). In order to evaluate off-street pedestrian facilities, average pedestrian space (m2/ped) has been used as the measuring parameter. The service categories predicted by the developed model for fifteen randomly selected segments has been compared with the observed ones. The high value found for exact matching (86.7 %) denotes well applicability of this developed model.