In recent years, automated traffic signal performance measures (ATSPMs) have emerged as a means of developing situational awareness of traffic conditions at intersections and assessing the quality of signal operations. As a growing number of agencies are adopting the technology, there is a need to understand how detector configurations can influence the outcomes of an analysis using ATSPM. Current practices with regard to detector configuration vary considerably from one agency to another; at one extreme, agencies may use one single detector input channel per phase without considering where the detectors are located, whereas at the other extreme, some agencies may utilize all possible channels to observe each individual lane at multiple positions. There are also variations in the design of detection zones (lengths and positions). This study takes on the problem in two parts. The first of these examines the impact of stop bar detection zone length and lane- or approach-based detector assignment on the ability of performance measures to identify accurately whether split failures occur. The second part examines the impact of setback detector distance on the use of a “percentage on green” metric that serves as a proxy measurement of the number of stops. The paper presents recommendations for performance measure calibrations and detector configurations that follow from these outcomes.

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Probe vehicle data have been extensively used to assess the performance of roadway systems, particularly the interstate highway system. High-resolution data from traffic signal controllers is another data source used for automated traffic signal performance measures (ATSPM), which is increasingly used to evaluate signal operation. As high-resolution data require additional resources and may not always be available, probe vehicle data are sometimes used to evaluate signalized corridor operation. However, there has been little previous research comparing probe vehicle data on signalized corridors with ATSPM. In this study, we compared the average speeds from probe vehicle data with ATSPMs to examine the degree of correlation between the two datasets. Different scenarios including segments with random arrivals and platoons were considered for parts of US 20 in Dubuque, Iowa. Regression analysis was performed with average speed as the dependent variable to check the correlation between the two datasets. Four different signal performance measures, namely the percent on green, volume-to-capacity ratio, percent of green duration, and average delay, were used as independent variables. Two sets of categorical variables representing time-of-day and day-of-week variables were also added. It was found that there exists good correlation between the datasets, supporting the use of probe vehicle data for corridor-level analysis in the absence of high-resolution data. Additionally, the durations of the intervals used for data aggregation were varied to check its impact on the correlation. Higher levels of aggregation resulted in better correlation between the two datasets.

Abstract:Pedestrians are an important element of the traffic stream especially in a country like Bangladesh. Dhaka is the biggest metropolitan city of Bangladesh and thus people from different parts of the country are relocating to Dhaka. This has rendered Dhaka one of the most densely populated cities in the World. With the resource restraint and crumbling infrastructure, the transportation facilities can't cope up with the ever growing population. A major proportion of the population are the urban slum dwellers and low income people who are left with the only option of walking. Pedestrians are the most vulnerable roadway users. Ironically they are not given due consideration in the design of roadway features. However, the alarming growths of pedestrians, inadequate sidewalks and their haphazard movement have forced them to share the carriageway with the vehicles. This has led to a shocking number of accidents in the past as well as contributed to further increasing the congestion on the carriageway. This study has attempted to present flow characteristics of pedestrians on exclusive sidewalks in three important urban areas of Dhaka namely Farmgate, Shahbag and Shukrabad. Pedestrian flow, density and walking speed are considered as the three primary parameters on which the flow characteristics depend. These are essential tools for determining the sidewalk capacity which will help in sidewalk design improvements required. The relationships between the three parameters were expressed in terms of three equations which makes it easy to comprehend the situations in these three locations. The level of service (LOS) has been determined at each location also. On the basis of flow rate, Farmgate has a LOS C and Shukrabad and Shahbag both have a LOS B. The average free-flow speed from three locations is about 1.18 m/s. This might help create an idea about the rate at which pedestrians might clear out from facilities.

The concept of resonant cycle length, that there are certain cycle lengths that may provide excellent progression owing to corridor geometry and other factors, has some currency as a potential strategy for cycle length selection. Past studies have identified resonant cycles under certain conditions and demonstrated benefits from use of the strategy as a means of selecting cycle length. The present study revisited the concept in application to flow-based models of traffic signal performance, highlighting the impact of phase sequence optimization. The phenomenon of cycle length resonance was explored for corridors with equal and randomly generated spacing between intersections, and finally for a field-calibrated corridor. Under each scenario, the performance of different cycle lengths was explored under two optimization strategies: optimization of only offsets, and optimization of both offsets and phase sequence. It was found that phase sequence has a substantial impact on the performance of coordination. Optimized phase sequences were found to yield 8% to 14% improvement in performance compared with use of the default sequence. For corridors where a resonant cycle length was evident, when phase sequences could also be adjusted, the poorer performance of non-resonant cycle lengths could be mitigated by optimizing phase sequence. Although use of a resonant cycle length is likely to yield good performance for some corridors under appropriate conditions, the use of a phase sequence optimization strategy is likely to have a strong impact on most corridors, and could be more impactful than selection of a resonant cycle length.