Effects of traffic signal coordination on the safety performance of urban arterials

Urban traffic congestion and crashes have been considered by city planners as critical challenges to the economic development of the city. Traffic signal coordination, which connects a series of signals along an arterial by various coordination methodologies, has been proved as one of the most cost-effective means of reducing traffic congestion. In this regard, Metropolitan Planning Organizations (MPO) or Transportation Management Centers (TMC) have included signal timing coordination in their strategic plans. Nevertheless, concerns on the safety effects of traffic signal coordination have been continuously raised by both transportation agencies and the public. This is mainly because signal coordination may increase the travel speed along an arterial, which increases the risk and severity of traffic collisions. To date, there is neither solid evidence from the field to support the concern, nor theoretical-level models to analyze this issue. This research aims to investigate the effects of traffic signal coordination on the safety performance of urban arterials through microsimulation modeling of two traffic operational conditions: free signal operation and coordinated signals, respectively. Three urban arterials in Reno, Nevada were selected as the simulation testbed and were coded in the PTV VISSIM software. The simulated trajectory data were analyzed by the Surrogate Safety Assessment Model (SSAM) to estimate the number of traffic conflicts. Sensitivity analyses were conducted for various traffic demand levels. Results show that under unsaturated conditions, traffic signal coordination could reduce the number of conflicts in comparison with the free signal operation condition. However, under oversaturated conditions, no significant difference was found between coordinated and free signal operations. Findings from this research indicate that traffic signal coordination has the potential to reduce the risk of crashes on urban arterials under unsaturated conditions.

An Overlapping Phase Approach to Optimize Bus Signal Priority Control under Two-Way Signal Coordination on Urban Arterials

With the consideration of the uneven traffic volume distribution at intersections on urban arterials, this paper aims to minimize the overall passenger delay (buses and private vehicles) at intersections and identify the applicable conditions of the proposed method with field data. The overlapping phase-based signal control logic and the bus priority control algorithm under two-way signal coordination on arterial roads are proposed. The vehicular capacities and occupancies for buses and passenger cars are considered in the evaluation of the method performance. A field test was carried out at two major intersections on an arterial road in Hefei, China. With the test data, the proposed method is examined and the possible influencing factors are analyzed for identifying the corresponding applicable conditions. The analysis result shows that the application of the overlapping phase helps to provide a relatively flexible signal control for the varying traffic demands at intersections. Compared to the conventional phase, it isof more practical significance to consider overlapping phase and apply bussignal priority control under two-way signal coordination according to the condition of uneven traffic volumedistribution at intersections on urban arterials. The proposed method can effectively decrease the total passenger delay at the intersections on urban arterials under certain applicable conditions. The possible factors influencing the method applicability are identified as well. It is verified that bus signal priority control under the two-way signal coordination, based on overlapping phases, is more conducive to improving traffic efficiency on urban arterials. Regarding the influencing factors and the applicability of the proposed method, the results show that not all situations are conducive to decreasing passenger delay at intersections. The proposed method should be applied under certain applicable conditions and principles in order to efficiently and effectively improve the traffic efficiency on arterial roads.

An Improved CTM Model for Urban Signalized Intersections and Exploration of Traffic Evolution

In this paper is going to be proposed a Cell Transmission Model (CTM), its analysis and evaluation with a case study, which addresses in a detailed way the aspect of merging and diverging operations on urban arterials. All those few CTM models that have been developed so far, to model intersections, have some limitations and drawbacks. First, unlike the simple composition road networks, such as highways, urban arterials must include some complex parts called merge sand diverges, due to the fact of vibrational values of reduced capacity, reduced saturation flow rate, etc. In order to simulate an urban network/arterial it is not possible to neglect the traffic signal indication on the respective time step. The objective of this paper is to highlight the difference between the results of the original CTM and our proposed CTM and to provide evidence that the later one is better than the old one. The proposed and formulated model will be employed through an algorithm of CTM to model a segment- arterial road of Pristina (compound from signalized intersections). For the functionalization and testing of the proposed model is build the experimental setup that is compatible with the algorithm created on C# environment. Results show that the proposed model can describe light and congested traffic condition. In light traffic conditions, in great mass traffic flow is dictated by the traffic signal status, while in medium congestion is obtained a rapid increase of the density to each cell. Fluctuations of the density from the lowest to the highest values are obvious during the first three cycles to all cells of the artery in a congested traffic state. Doi: 10.28991/cej-2021-03091659 Full Text: PDF

Analysis of accident duration on urban arterials roads

Acidentes de trânsito são o principal fator para a formação de congestionamentos não recorrentes em vias urbanas e responsáveis por gerar atrasos inesperados aos usuários do sistema. Entender o comportamento da duração desses acidentes e identificar os seus fatores explicativos pode conduzir para um gerenciamento mais eficiente do tráfego urbano. Buscando contribuir com essa problemática, este trabalho teve como objetivo analisar a duração de acidentes de trânsito ocorridos em vias urbanas da cidade de Fortaleza-CE. Inicialmente, um método para detectar a duração dos acidentes a partir de dados de tráfego de equipamentos de fiscalização eletrônica foi proposto, dada a indisponibilidade dessa informação no banco de dados de acidentes de trânsito. Como resultados, a duração dos 324 acidentes detectados teve uma média de 72 minutos e uma dispersão de 48 minutos. A função densidade de probabilidade Gamma apresentou o melhor ajuste à duração dos acidentes, indicando que essa variável é influenciada por eventos que ocorrem ao longo do tempo, aumentando a probabilidade de o acidente ser resolvido. A análise mostrou que fatores relacionados ao atendimento dos acidentes, ao comportamento dos indivíduos, ao número de veículos envolvidos e ao local de ocorrência (meio de quadra ou interseção) podem estar influenciando a duração dos acidentes. Entretanto, não foram encontrados indícios de que a duração dos acidentes é influenciada pela sua gravidade (acidentes com ou sem vítimas) ou pela sua natureza.

Alternatives to Improve Operational Traffic in Roundabouts Using Microsimulation

Roundabout in urban arterials are likely to block roads or generate long queues of vehicles due to the constant changes on urban dynamics near to the interception. Several alternatives to modify the flow pattern or geometry and infrastructure need to be study previously to propose a final design solution of roundabout with traffic issues. In this study, a review of three alternatives to improve the operational traffic are discussed; signalized intersection, turbo-roundabouts and overpass/underpass. In addition, the application of these alternatives is evaluated in a “classic” roundabout located at Tunja city that has a maximum of 3691 Veh/h counted and it is operated in saturated condition. Microsimulation is used from a calibrated model with volume counted, vehicle composition and speeds in the VISSIM software. Results show that signalize the roundabout does not improve the operational traffic (with a reduction on 38% of approach speed) and, the turbo-roundabouts are a mid-term solution that meet the traffic demand on 15 years with a progressively loss of service (with a mean approach speed of 6.4 Km/h at 15 years). The constructions of underpass and overpass show to be the only solution that increase four times the travel speed throw the roundabout and keep acceptable speed at the end of cyclic live of intersection (18.7 Km/h at 20 years).