Field Measurement of Signalized Intersection Delay for 1997 Update of the Highway Capacity Manual

1998 ◽  
Vol 1646 (1) ◽  
pp. 79-86 ◽  
Author(s):  
James L. Powell
Keyword(s):  
Field Measurement ◽  
Flow Speed ◽  
Signalized Intersection ◽  
Volume Control ◽  
Level Of Service ◽  
Highway Capacity ◽  
Total Delay ◽  
Highway Capacity Manual ◽  
Measuring Field ◽  
Vehicle Deceleration

The 1997 update of the Highway Capacity Manual changes the basis of delay for level-of-service determination at signalized intersections from stopped delay to conceptually more appealing total delay. Total delay is made up of components including volume, control, and geometric delay. Level of service is now defined in terms of control delay, which provides a more stable and tractable relation to total delay, but the issue of field measurement remains in any case. A combined theoretical and empirical approach to measuring field delay on the basis of typical vehicle deceleration and acceleration profiles is taken in this paper. The profiles are related to the relatively easily surveyed quantity of vehicles in queue, which is equivalent to estimating time in queue of all vehicles stopped by the traffic signal. The results indicate that after vehicles in queue are sampled, correction factors can account, in practical terms, for the unsurveyed deceleration and acceleration delay. The corrections are simple additive factors that are a function of free-flow speed and average number of vehicles stopped in queue. Another adjustment is included for the consistent tendency of human observers to overestimate vehicles in queue. All of these factors are included in the new 1997 HCM procedure for measuring signalized intersection delay in the field. Further identified work includes the need to fully develop the total delay concept to account for geometric delay consistently over a variety of interrupted- and uninterrupted-flow facilities. Such resolution should be included in HCM 2000 preparation currently in progress.

Application of Moving Car Observer Method for Measuring Free Flow Speed on Two-lane Highways

2014 ◽  
Vol 69 (6) ◽  
Author(s):  
Othman Che Puan ◽  
Muttaka Na’iya Ibrahim ◽  
Usman Tasiu Abdurrahman
Keyword(s):  
Field Measurement ◽  
Flow Speed ◽  
Operating Conditions ◽  
Free Flow ◽  
Geometric Features ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Free Flow Speed ◽  
The Subject ◽  
Low Traffic

There exists a need to evaluate the performance indicator that reflects the current level of service (LOS) of the subject facility to justify any decision making on expenditures to be made for improving the performance level of a road facility. Free-flow speed (FFS) is one of the key parameters associated with LOS assessment for two-lane highways. Application of a more realistic approach for assessing road’s performance indicators would result in better estimates which could in turn suggest the most appropriate decision to be made (for situations where upgrading is needed); especially, in terms of finance, materials and human resources. FFS is the driver’s desired speed at low traffic volume condition and in the absence of traffic control devices. Its estimation is significant in the analysis of two-lane highways through which average travel speed (ATS); an LOS indicator for the subject road class is determined. The Highway Capacity Manual (HCM) 2010 offers an indirect method for field estimation of FSS based on the highway operating conditions in terms of base-free-flow-speed (BFFS). It is however, recommended by the same manual that direct field FSS measurement approach is most preferred. The Malaysian Highway Capacity Manual (MHCM) established a model for estimating FFS based on BFFS, the geometric features of the highway and proportion of motorcycles in the traffic stream. Estimating FFS based on BFFS is regarded as an indirect approach which is only resorted to, if direct field measurement proved difficult or not feasible. This paper presents the application of moving car observer (MCO) method for direct field measurement of FFS. Data for the study were collected on six segments of two-lane highways with varying geometric features. FFS estimates from MCO method were compared with those based on MHCM model. Findings from the study revealed that FFS values from MCO method seem to be consistently lower than those based on MHCM model. To ascertain the extent of the difference between the FFS values from the two approaches, student t-statistics was used. The t-statistics revealed a P–value of less than 0.05 (P < 0.05) which implies that there is a statistically significant difference between the two sets of data. Since MCO method was conducted under low traffic flow (most desired condition for field observation), it can be suggested that MCO estimates of FFS represent the actual scenario. A relationship was therefore developed between the estimates from the two methods. Thus, if the MHCM model is to be applied, the measured value needs to be adjusted based on the relationship developed between the two approaches.

scholarly journals Self-Organizing Tree Algorithm (SOTA) Clustering for Defining Level of Service (LOS) Criteria of Urban Streets

2018 ◽  
Vol 47 (4) ◽  
pp. 309-317
Author(s):  
Amit Kumar Das ◽  
Prasanta Kumar Bhuyan
Keyword(s):  
Travel Speed ◽  
Flow Speed ◽  
Free Flow ◽  
Level Of Service ◽  
Highway Capacity ◽  
Tree Algorithm ◽  
Highway Capacity Manual ◽  
Urban Streets ◽  
Flow Speeds ◽  
Self Organizing

This study is intended to define the Free Flow Speed (FFS) ranges of urban street classes and speed ranges of Level of Service (LOS) categories. In order to accomplish the study FFS data and average travel speed data were collected on five urban road corridors in the city of Mumbai, India. Mid-sized vehicle (car) mounted with Global Positioning System (GPS) device was used for the collection of large number of speed data. Self-Organizing Tree Algorithm (SOTA) clustering method and five cluster validation measures were used to classify the urban streets and LOS categories. The above study divulges that the speed ranges for different LOS categories are lower than that suggested by Highway Capacity Manual (HCM) 2000. Also it has been observed that average travel speed of LOS categories expressed in percentage of free flow speeds closely resembles the percentages mentioned in HCM 2010.

Phase Time Prediction for Traffic-Actuated Intersections

1996 ◽  
Vol 1555 (1) ◽  
pp. 17-22 ◽  
Author(s):  
Pei-Sung Lin ◽  
Kenneth G. Courage
Keyword(s):  
Field Studies ◽  
Signalized Intersection ◽  
Level Of Service ◽  
Signal Timing ◽  
Highway Capacity ◽  
Traffic Demand ◽  
Highway Capacity Manual ◽  
Time Prediction ◽  
Traffic Characteristics ◽  
General Reliability

The Highway Capacity Manual (HCM) provides a methodology in Chapter 9 to estimate the capacity and level of service at a signalized intersection as a function of traffic characteristics and signal timing. At traffic-actuated intersections, the signal timing changes from cycle to cycle in response to traffic demand. An accurate prediction of average phase times and their corresponding cycle length is required to assess the performance of intersections controlled by traffic-actuated signals. The current technique suggested in Appendix II of HCM Chapter 9 for this purpose has not been well accepted. A more comprehensive methodology and a more satisfactory analytical model are described that predict traffic-actuated signal timing for both isolated and coordinated modes with actuated phases. The proposed methodology and model have been verified by simulation augmented by limited field studies. The results are encouraging with respect to their general reliability and their compatibility with the current HCM Chapter 9 structure.

Proposed Framework for Evaluating Spillback in the Highway Capacity Manual

2017 ◽  
Vol 2615 (1) ◽  
pp. 148-158
Author(s):  
Yinan Zheng ◽  
Michael Armstrong ◽  
Gustavo de Andrade ◽  
Lily Elefteriadou
Keyword(s):  
Signalized Intersection ◽  
Level Of Service ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Urban Streets ◽  
Facility Type ◽  
Street Intersection ◽  
Lane Utilization ◽  
New Procedures ◽  
Data Collection Effort

Procedures detailed in the Highway Capacity Manual 2010 (HCM 2010) estimate capacity and several operational measures dictating level of service for freeway facilities and surface streets. However, these methods do not consider cases in which spillback occurs from one facility type to another. The queuing effects in oversaturated conditions as they propagate upstream onto a freeway main line or a surface street intersection are not accounted for. The objective of this paper is to propose a series of modifications to enhance the HCM 2010 methods to address spillback conditions. These modifications consider lane utilization and lane blockage under spillback conditions and consist of restructuring existing equations and reference tables as well as developing new procedures. A four-regime method is proposed for evaluating spillback effects from urban streets to diverge and weaving segments. In addition, a method is proposed to account for the spillback effects from freeway on-ramps by reducing the effective green time as a proportion of the percent of time that the queue is expected to block the upstream signalized intersection. The framework developed uses assumptions that should be further explored through an extensive, nationwide data collection effort.

Development of ‘Speed Ratio’ Based Level of Service Criteria on Undivided Urban Streets in Mixed Traffic Context

2020 ◽  
Author(s):  
Subhadip Biswas ◽  
Ashutosh Pandey
Keyword(s):  
Clustering Algorithms ◽  
Flow Speed ◽  
Urban Traffic ◽  
Level Of Service ◽  
Speed Ratio ◽  
Agglomerative Clustering ◽  
Highway Capacity ◽  
Traffic Condition ◽  
Rapid Urbanization ◽  
Highway Capacity Manual

Developing countries are facing challenges in sustaining urban traffic congestion due to rapid urbanization. In order to manage urban traffic, a traffic engineer first need to assess the current operational condition on urban roads. ‘Level of Service (LOS)’ is used to define the operational traffic condition within a traffic stream in terms of service quality that a facility is providing to its user. This paper proposes a novel approach to estimate ‘Speed Ratio’ by considering individual Free-Flow Speed (FFS) of different vehicle categories. This study also provides a comparison between FFS estimated using the methods given in Highway Capacity Manual 2010 and Indian-Highway Capacity Manual 2018. LOS criteria was developed using five clustering technique; K-means, K-medoids, Clustering Large Applications, Fuzzy-C Means and Hierarchical Agglomerative Clustering. Both internal and external cluster validation indices were used to find the optimal number of clusters and suitable clustering algorithms.

Modeling Capacity of Through Movement at Signalized Intersection Affected by Short Left-Turn Bay under Different Signal Settings

2021 ◽  
pp. 036119812110064
Author(s):  
Zihang Wei ◽  
Yunlong Zhang ◽  
Xiaoyu Guo ◽  
Xin Zhang
Keyword(s):  
Cycle Length ◽  
Signalized Intersections ◽  
Signalized Intersection ◽  
Essential Factor ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Proposed Model ◽  
Vehicle Demand ◽  
The One

Through movement capacity is an essential factor used to reflect intersection performance, especially for signalized intersections, where a large proportion of vehicle demand is making through movements. Generally, left-turn spillback is considered a key contributor to affect through movement capacity, and blockage to the left-turn bay is known to decrease left-turn capacity. Previous studies have focused primarily on estimating the through movement capacity under a lagging protected only left-turn (lagging POLT) signal setting, as a left-turn spillback is more likely to happen under such a condition. However, previous studies contained assumptions (e.g., omit spillback), or were dedicated to one specific signal setting. Therefore, in this study, through movement capacity models based on probabilistic modeling of spillback and blockage scenarios are established under four different signal settings (i.e., leading protected only left-turn [leading POLT], lagging left-turn, protected plus permitted left-turn, and permitted plus protected left-turn). Through microscopic simulations, the proposed models are validated, and compared with existing capacity models and the one in the Highway Capacity Manual (HCM). The results of the comparisons demonstrate that the proposed models achieved significant advantages over all the other models and obtained high accuracies in all signal settings. Each proposed model for a given signal setting maintains consistent accuracy across various left-turn bay lengths. The proposed models of this study have the potential to serve as useful tools, for practicing transportation engineers, when determining the appropriate length of a left-turn bay with the consideration of spillback and blockage, and the adequate cycle length with a given bay length.

Estimating the Effects of Urban Street Incidents on Capacity

2017 ◽  
Vol 2615 (1) ◽  
pp. 55-61 ◽  
Author(s):  
Aidin Massahi ◽  
Mohammed Hadi ◽  
Maria Adriana Cutillo ◽  
Yan Xiao
Keyword(s):  
Network Performance ◽  
Field Measurements ◽  
Signalized Intersection ◽  
Limited Information ◽  
Microscopic Simulation ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Urban Streets ◽  
Urban Street ◽  
Incident Duration

The effect of incidents on capacity is the most critical parameter in estimating the influence of incidents on network performance. The Highway Capacity Manual 2010 (HCM 2010) provides estimates of the drop in capacity resulting from incidents as a function of the number of blocked lanes and the total number of lanes in the freeway section. However, there is limited information on the effects of incidents on the capacity of urban streets. This study investigated the effects on capacity of the interaction between the drop in capacity below demand at a midblock urban street segment location and upstream and downstream of signalized intersection operations. A model was developed to estimate the drop in capacity at the incident location as a function of the number of blocked lanes, the distance from the downstream intersection, and the green time–to–cycle length (g:C) ratio of the downstream signal. A second model was developed to estimate the reduction in the upstream intersection capacity resulting from the drop in capacity at the midblock incident location as estimated by the first model. The second model estimated the drop in capacity of the upstream links feeding the incident locations as a function of incident duration time, the volume-to-capacity (V/C) ratio at the incident location, and distance from an upstream signalized intersection. The models were developed on the basis of data generated with the use of a microscopic simulation model calibrated by comparison with parameters suggested in HCM 2010 for incident and no-incident conditions and by comparison with field measurements.

Uncertainty in Operational Analysis of Two-Lane Highways

2002 ◽  
Vol 1802 (1) ◽  
pp. 105-114 ◽  
Author(s):  
R. Tapio Luttinen
Keyword(s):  
Input Data ◽  
Travel Speed ◽  
Level Of Service ◽  
Model Parameters ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Operational Analysis ◽  
Percent Time ◽  
Different Types ◽  
Percent Time Spent Following

The Highway Capacity Manual (HCM) 2000 provides methods to estimate performance measures and the level of service for different types of traffic facilities. Because neither the input data nor the model parameters are totally accurate, there is an element of uncertainty in the results. An analytical method was used to estimate the uncertainty in the service measures of two-lane highways. The input data and the model parameters were considered as random variables. The propagation of error through the arithmetic operations in the HCM 2000 methodology was estimated. Finally, the uncertainty in the average travel speed and percent time spent following was analyzed, and four approaches were considered to deal with uncertainty in the level of service.

Comparison of Planning and Operational Analysis Procedures for Signalized Intersections from the Highway Capacity Manual

1996 ◽  
Vol 1555 (1) ◽  
pp. 59-64
Author(s):  
Mark R. Virkler ◽  
Shashi Gannavaram ◽  
Anand Ramabhadran
Keyword(s):  
Level Of Service ◽  
Signal Timing ◽  
Highway Capacity ◽  
Operational Procedure ◽  
Highway Capacity Manual ◽  
Operational Analysis ◽  
Planning Procedure ◽  
Adjustment Factors ◽  
Cycle Lengths ◽  
Traffic Signal Timing

The 1994 update of the Highway Capacity Manual (HCM) includes a planning procedure to estimate the capacity condition of a signalized intersection (Xcm). The planning method results can also be extended to a planning application of the more data-intensive HCM operational procedure to estimate intersection critical flow-to-capacity ratio (Xc) and level of service with only planning-level data. Both the planning procedure and the planning application of the operational procedure involve default adjustment factors and synthesized traffic signal timing (called the “default signal timing”). Data from 166 Missouri intersections were used to determine how well the planning approaches predict operational analysis results. In general, the default signal timings had shorter cycle lengths than the timing plans used at pretimed signals. The shorter cycle lengths led to slightly higher flow-to-capacity ratios, since a higher proportion of each cycle was devoted to lost time. The default signal timings also had more equal flow-to-capacity ratios within critical lane groups. The shorter cycle lengths and more equal flow-to-capacity ratios led to a predicted level of service that was the same or better than that calculated for actual conditions. For the subject intersections, locally calibrated default adjustment factors yielded better predictions of flow-to-capacity ratios and level of service than the HCM defaults. The planning value for Xcm was often less than the actual Xc for operational analysis of actual conditions. This was to be expected since Xcm is based on the maximum allowable cycle length. The HCM planning procedure is expected to receive wide use in a variety of planning and design applications. Calibration of appropriate local default values should improve the accuracy of the planning procedure results.

Delays of Shared-Short Lanes at Unsignalized Intersections

2019 ◽  
Vol 2673 (8) ◽  
pp. 450-462
Author(s):  
Ning Wu ◽  
Werner Brilon
Keyword(s):  
Estimation Procedure ◽  
Level Of Service ◽  
Queuing Systems ◽  
Highway Capacity ◽  
Combined System ◽  
Total Delay ◽  
Average Delay ◽  
Unsignalized Intersections ◽  
Special Case ◽  
Total Average

At unsignalized intersections, both on the major street and on the minor street, there may be short turning lanes alongside the through lanes following downstream from one single lane. This combined system is termed a shared-short lane (SSL). Up to now it has only been possible to calculate the capacity of these lanes at the stop line and the capacity of the diverging point, where the turning lane diverges from the through lane. For the total average delay of the involved individual movements, there is no applicable estimation procedure. As a special case, the shared lane (SL), which is used by several movements without a separate turning lane, must also be reconsidered. This paper presents a new model for the estimation of average delays of SSL with SL as a special case at unsignalized intersections. The model is based on the analogy to standard queuing systems. The results depend on the length of the short lane. The model is validated by simulation. The results demonstrate that the outcome of the models in current highway capacity manuals may be misleading, with the risk of inaccurately classifying the level of service of an intersection. Therefore, there is an urgent need to complete the relevant procedures in highway capacity manuals by more realistic estimation procedures for the total delay at an SSL or an SL. The methods in this paper—even if they are rather complex—are recommended to be incorporated into future versions of highway capacity manuals using some simplifications.

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