Congestion analysis of unsignalized intersections

This paper considers an unsignalized intersection used by two traffic streams. A stream of cars is using a primary road, and has priority over the other, low-priority, stream. Cars belonging to the latter stream cross the primary road if the gaps between two subsequent cars on the primary road is larger than their critical headways. Questions that naturally arise are: given the arrival pattern of the cars on the primary road, what is the maximum arrival rate of low-priority cars such that the number of such cars remains stable? In the second place, what can be said about the delay experienced by a typical car at the secondary road? This paper addresses such issues by considering a compact model that sheds light on the dynamics of the considered unsignalized intersection. The model, which is of a queueing-theoretic nature, reveals interesting insights into the impact of the user behavior on the above stability and delay issues. The contribution of this paper is twofold. First, we obtain new results for the aforementioned model with driver impatience. Secondly, we reveal some surprising aspects that have remained unobserved in the existing literature so far, many of which are caused by the fact that the capacity of the minor road cannot be expressed in terms of the \emph{mean} gap size; instead more detailed characteristics of the critical headway distribution play a role.Comment: This paper appeared in the proceedings of the 8th International Conference on Communication Systems and Networks (COMSNETS), 5-10 Jan. 2016. A related but more extended paper which analyses a more general model than the one in the present paper can be also found on arXiv:1802.0673

Generalized gap acceptance models for unsignalized intersections

This paper contributes to the modeling and analysis of unsignalized intersections. In classical gap acceptance models vehicles on the minor road accept any gap greater than the CRITICAL gap, and reject gaps below this threshold, where the gap is the time between two subsequent vehicles on the major road. The main contribution of this paper is to develop a series of generalizations of existing models, thus increasing the model's practical applicability significantly. First, we incorporate {driver impatience behavior} while allowing for a realistic merging behavior; we do so by distinguishing between the critical gap and the merging time, thus allowing MULTIPLE vehicles to use a sufficiently large gap. Incorporating this feature is particularly challenging in models with driver impatience. Secondly, we allow for multiple classes of gap acceptance behavior, enabling us to distinguish between different driver types and/or different vehicle types. Thirdly, we use the novel M$^X$/SM2/1 queueing model, which has batch arrivals, dependent service times, and a different service-time distribution for vehicles arriving in an empty queue on the minor road (where `service time' refers to the time required to find a sufficiently large gap). This setup facilitates the analysis of the service-time distribution of an arbitrary vehicle on the minor road and of the queue length on the minor road. In particular, we can compute the MEAN service time, thus enabling the evaluation of the capacity for the minor road vehicles

Tradeoffs among Free-flow Speed, Capacity, Cost, and Environmental Footprint in Highway Design

This paper investigates differentiated design standards as a source of capacity additions that are more affordable and have smaller aesthetic and environmental impacts than expressways. We consider several tradeoffs, including narrow versus wide lanes and shoulders on an expressway of a given total width, and high-speed expressway versus lower-speed arterial. We quantify the situations in which off-peak traffic is sufficiently great to make it worthwhile to spend more on construction, or to give up some capacity, in order to provide very high off-peak speeds even if peak speeds are limited by congestion. We also consider the implications of differing accident rates. The results support expanding the range of highway designs that are considered when adding capacity to ameliorate urban road congestion.Highway design; Capacity; Free-flow speed; Parkway

Exploring Strategies to Improve Mobility and Safety on Roadway Segments in Urban Areas

Several strategies have been proposed and developed to alleviate the congestion and throughput problem usually experienced in urban areas. These strategies include the use of Intelligent Transportation Systems, signal re-timing and signal coordination, among others. In urban areas, there are often combinations of signalized and un-signalized intersections on corridors that may impact throughput and mobility. This research investigated driver compliance rate (CR) with STOP-signs at All-Way STOP Control (AWSC) intersections that are in close proximity to upstream or downstream signalized intersections. Also, strategies to improve mobility and throughput on segments in an urban area were explored via modeling and simulation. Thirty isolated segments with combinations of signalized and un-signalized intersections in the District of Columbia were selected for the study. Field data (traffic volumes, signal timing, lane configurations, etc.) were collected at each intersection of the segments. Driver compliance with STOP-signs at AWSC intersections within the segments was also observed. In all, 13,956 observations were made at 57 AWSC intersections. The segments were then modelled in the software program, and two scenarios were simulated. The “before” scenario simulated the existing conditions on the segments. In the “after” scenario, the AWSC intersections in each segment were signalized (and optimized), while maintaining the same conditions at the signalized intersections. Control delay and average travel speed were the measures of effectiveness (MOEs) that were used to assess the performance of the segments in both scenarios. The results of a regression analysis showed a positive relationship between CR and the distance between the existing AWSC and signalized intersections. A nonlinear regression model developed indicates that, to achieve a minimum compliance rate of 95%, a minimum distance of approximately 1,298 ft. between the intersections is required. Also, a test of comparison of means of the segments’ MOEs in the “before” and “after” scenarios showed significant improvements in the “after” scenarios. Statistically significant reductions in control delays on the segments were reported, while the average travel speed of vehicles significantly increased. The study revealed that even though some un-signalized intersections may not meet the MUTCD warrants for signalization, signalizing and coordinating them with existing signalized intersections will improve mobility and throughput

A new methodological framework for within-day dynamic estimation of pollutant emissions in a large congested urban network

This paper presents a new methodological framework to address the problem of estimating pollutant emissions for large congested urban networks in a within-day dynamic context. It consists of three main modules: 1) a module to compute pollutant emissions for general links; 2) a module to compute pollutant emissions for all links approaching a signalized intersection; 3) a module to compute pollutant emissions for all links approaching an unsignalized intersection. A dynamic mesoscopic assignment model is performed to derive the main dynamic input of each one of the modules. All the modules have been tested in a real case study (the district of Eur in the city of Rome, Italy), so confirming the reliability of the developed models and their applicability for the estimation of pollutant emissions

ANALISA KINERJA SIMPANG TIGA TAK BERSINYAL PADA SIMPANG JL. KEBONAGUNG – JL. WAGIR KECAMATAN PAKISAJI KABUPATEN MALANG JAWA TIMUR

Along with the development of a city, transportation needs are increasing and become one of the factors of traffic problems at intersections. Malang Regency is the main land transportation crossing between City in Jawa Timur and one of the intersections in Malang Regency is experiencing traffic problems, namely congestion. Congestion occurs during peak hours, precisely at the unsignalized intersection of Jl. Kebonagung – Jl. Wagir. The purpose of this study was to determine the performance of the unsignalized intersection of Jl. Kebonagung – Jl. Wagir, as well as knowing the right alternative solutions. Data obtained from primary surveys in the morning, afternoon dan evening, data were analyzed using the Indonesian Road Capacity Manual, 1997. The current condition shows that degree of saturation is not stable with the highest degree of saturation at 0.86 and a delay of 14,31 sec/pcu. The result of the analysis show that the most appropriate alternative solution for improving the performance of the intersection is the installation of a road widening, the highest degree of saturation is 0.81 and the highest delay is 13,61 sec/pc

TRAFFIC FLOW ANALYSIS AT UNSIGNAL JUNCTION (CASE STUDY: INTERSECTION OF JL. MANDALA – JL. RAYA TLANAKAN PAMEKASAN CITY)

We often find traffic problems in big cities, and even small cities such as Pamekasan. The problem of congestion and traffic congestion often occurs at crossroads, especially the intersection of Jl. Mandala – Jl. Raya Tlanakan, Pamekasan City. The reduced performance of the intersection will cause losses due to a decrease in speed, an increase in delays and vehicle queues and a decrease in environmental quality. Parameters of an unsignalized intersection include capacity, degree of saturation, delay and queuing opportunity. From the analysis, the maximum C (capacity) value of 2257.83 smp/hour does not exceed the basic capacity (Co = 2700 smp/hour). The low capacity classification occurring on Thursday, December 9, 2021 at 18.00 – 21.00 WIB. The highest DS (Degree of Saturation) value is 0.63, and the largest D (Intersection Delay) value is 19.17 sec/smp occurred on Thursday, December 9, 2021 at 06.00 – 10.00 WIB. Then the capacity obtained at the intersection of Jl. Mandala – Jl. Raya Tlanakan, Pamekasan City is still feasible to accommodate the traffic volume because it does not exceed the basic capacity of the intersection. However, to overcome congestion at intersections, especially during rush hour/working hours, it is necessary to supervise and secure from related parties

Congestion analysis of unsignalized intersections: The impact of impatience and Markov platooning

This paper considers an unsignalized intersection used by two traffic streams. A stream of cars is using a primary road, and has priority over the other stream. Cars be-longing to the latter stream cross the primary road if the gaps between two subsequent cars on the primary road are larger than their critical headways. A question that naturally arises relates to the capacity of the secondary road: given the arrival pattern of cars on the primary road, what is the maximum arrival rate of low-priority cars that can be sustained? This paper addresses this issue by considering a compact model that sheds light on the dynamics of the considered unsignalized intersection. The model, which is of a queueing-theoretic nature, reveals interesting insights into the impact of the user behavior on stability.The contributions of this paper are threefold. First, we obtain new results for the afore-mentioned model that includes driver impatience. Secondly, we reveal some surprising aspects that have remained unobserved in the existing literature so far, many of which are caused by the fact that the capacity of the minor road cannot be expressed in terms of the mean gap size; instead more detailed characteristics of the critical headway distribution play a crucial role. The third contribution is the introduction of a new form of bunching on the main road, called Markov platooning. The tractability of this model allows us to study the impact of various platoon formations on the main road on the capacity of the minor road.</p

Traffic Flow Analysis and Solutions to Ease Traffic Flow at Unsignalized Taxila Intersection

Transportation system of a city affects all aspects of its citizen’s economic and personal activities. At a general level, the traffic problem considered as a situation of mismatch between supply (i.e., roads and their capacity) and demands (i.e., travel needs). The city administrators have tried to balance it by creating infrastructures (e.g., new roads, expanding capacity, under pass) or policy changes (e.g., banning heavy traffic movement during peak or day hours). Major problems that motorists are facing on highways intersection are congestion, accidents, and costs. Too many automobiles, trucks, buses, bicycles, and pedestrians are attempting to use the same space to reach their destiny. N-5 (major highway in Pakistan) passes through Taxila where at some intersection extreme traffic congestion sets in. Transportation problems are evident at some locations with complex roadway geometrics. So a traffic study is to be conducted to quantify the extent of transportation problems. This study aims to gain information and understanding about traffic system through the derivation of traffic information from traffic data, and then to apply this information in the assessment of the performance of traffic systems and their interaction with land use activities. This research is an effort to provide suggestion and recommendations to enforce an efficient traffic flow system