Variations in Capacity at Signalized Intersections with Different Area Types

2000 ◽  
Vol 1710 (1) ◽  
pp. 199-204 ◽  
Author(s):  
Xuewen Le ◽  
Jian Lu ◽  
Edward A. Mierzejewski ◽  
Yanhu Zhou
Keyword(s):  
Signalized Intersections ◽  
Capacity Analysis ◽  
Adjustment Factor ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Central Florida ◽  
Start Up ◽  
Study Results ◽  
Lost Time

The capacity analysis procedure for signalized intersections included in the Highway Capacity Manual (HCM) needs to consider the area type of a given intersection. The area-type adjustment factor used in the procedure is based on conclusions from a limited number of studies. In addition, the procedure for using an area-type adjustment factor is not well defined in the HCM. A study undertaken in central Florida to study the effects of four different area types on the capacity of signalized intersections is summarized. These four area types include recreational, business, residential, and shopping. Study results indicated that differences in saturation headways among different area types were significant. The saturation headways observed in recreational areas were significantly higher than those in other areas for both left-turn and through movements. The through-movement saturation headways obtained in residential, shopping, and business areas were not significantly different. This study resulted in a new area-type adjustment factor of 0.92 for recreational areas, whereas the factor is 1.00 for other areas. Results in this study also indicated that the differences in start-up lost time among different area types were not significantly different. In addition, according to the results of the analysis, 75 percent of the yellow interval in undersaturated conditions and 35 percent of the yellow interval in oversaturated conditions were found to be unused and considered clearance lost time.

Estimating Intersection Approach Delay Using 1985 and 1994 Highway Capacity Manual Procedures

1996 ◽  
Vol 1555 (1) ◽  
pp. 23-32
Author(s):  
Stephen M. Braun ◽  
John N. Ivan
Keyword(s):  
Field Measurements ◽  
Signalized Intersections ◽  
New Technique ◽  
Adjustment Factor ◽  
Highway Capacity ◽  
Flow Rates ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
A New Technique ◽  
Saturation Flow

The current methods for determining average stopped delay at signalized intersections were studied. Field measurements of average stopped delay were obtained and compared with values computed using both the 1985 and 1994 editions of the Highway Capacity Manual (HCM). The 1994 HCM uses an equation to predict the progression adjustment factor (PF), a new technique for determining the left-turn adjustment factor for saturation flow rates, and a new set of equations for determining the uniform delay parameter for left-turn lane groups with primary and secondary phasing. Overall, the 1994 HCM produces better estimates of intersection stopped delay than the 1985 HCM.

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.

Arrival-Based Uniform Delay Model for Oversaturated Signalized Intersections with Poor Progression

2005 ◽  
Vol 1920 (1) ◽  
pp. 86-94
Author(s):  
Rahim F. Benekohal ◽  
Sang-Ock Kim
Keyword(s):  
Signalized Intersections ◽  
Delay Model ◽  
Adjustment Factor ◽  
Highway Capacity ◽  
New Approach ◽  
Highway Capacity Manual ◽  
Traffic Conditions ◽  
Proposed Model ◽  
Uniform Delay ◽  
Control Delays

For oversaturated traffic conditions, the Highway Capacity Manual (HCM) does not apply a progression adjustment factor to the delay model for signalized intersections when there is an initial queue. This causes counterintuitive results in the calculation of delay; for some cases, delay for a nonzero initial queue condition ends up being less than the delay with zero initial queue conditions. Also, for oversaturated traffic conditions, the delay model in the 2000 edition of HCM yields the same uniform delay values for all arrival types when there is an initial queue. This does not seem reasonable because it ignores the effect of platooning on delay. This paper introduces a new approach for computing uniform delay for oversaturated traffic conditions when progression is poor. This approach directly considers the platooning effects in delay and thus eliminates the need to apply a progression adjustment factor. The proposed model is applicable whether there is an initial queue or not. The approach was validated by a comparison of the control delays obtained from a CORSIM simulation to the delays from the proposed model. Validation procedures were conducted on the basis of zero and nonzero initial queue conditions. The proposed approach resulted in more accurate delay values than the HCM model.

Utilization of Auxiliary Through Lanes at Signalized Intersections with Downstream Lane Reductions

1997 ◽  
Vol 1572 (1) ◽  
pp. 167-173 ◽  
Author(s):  
Jamie W. Hurley
Keyword(s):  
Signalized Intersections ◽  
Stepwise Multiple Regression ◽  
Distribution Data ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Traffic Characteristics ◽  
Geometric Factors ◽  
Auxiliary Through Lanes ◽  
Right Turns

The capacity of multiple through lanes at signalized intersections depends on the distribution of traffic within these lanes, with equal lane distribution corresponding to maximum capacity. However, traffic characteristics, land use, and geometric factors usually prohibit this from occurring. Although the 1994 update of the Highway Capacity Manual considers the case of continuous through lanes at signalized intersections, the default values provided do not address situations in which lane reduction takes place downstream of the intersection. Lane distribution data obtained in the field can remedy the situation but for existing conditions only. This research employed the concept of captive and choice lane users in modeling lane use for intersection configurations with a single continuous through lane and an “auxiliary” through lane, which is continuous upstream of the intersection but is dropped downstream of it. Stepwise multiple regression was performed on data collected at sites in Tennessee to ascertain those factors significantly affecting auxiliary lane use. These factors were found to be ( a) right turns off the facility at the intersection, ( b) total left turns off the facility downstream of the intersection, ( c) right turns onto the facility in the first 122 m (400 ft) upstream of the intersection, ( d) right turns off the facility in the last 152 m (500 ft) of the auxiliary lane, ( e) downstream auxiliary lane length, and ( f) the existence of left-turn bays or two-way continuous left-turn lanes downstream of the intersection. For the configuration studied, lane distribution data often differed considerably from the default values given in the Highway Capacity Manual.

Saturation Flow Rate, Start-Up Lost Time, and Capacity for Bicycles at Signalized Intersections

2003 ◽  
Vol 1852 (1) ◽  
pp. 105-113 ◽  
Author(s):  
Winai Raksuntorn ◽  
Sarosh I. Khan
Keyword(s):  
Flow Rate ◽  
Field Studies ◽  
Signalized Intersections ◽  
Highway Capacity Manual ◽  
Start Up ◽  
Lost Time ◽  
Saturation Flow Rate ◽  
Saturation Flow ◽  
Bicycle Lane ◽  
Stop Line

A review of the literature shows that capacity and saturation flow rate for on-street bicycle lanes at intersections have not been measured on the basis of bicycle discharge at intersections at the start of the green phase. The Highway Capacity Manual 2000 recommends a saturation flow rate of 2,000 bicycles per hour for a bicycle lane at a signalized intersection. However, this recommendation is not based on field studies at the intersection and is not a function of the width of the bicycle lane. A revised estimate is provided of saturation flow rate, and an estimate is provided of start-up lost time for bicycles based on data collected at the stop line of signalized intersections. In addition, the lateral stopped distance of automobiles from bicycle lanes, the lateral stopped distance of bicycles from adjacent lanes, and the lateral and longitudinal stopped distance between pairs of bicycles at a signalized intersections are presented. Bicycles may form more than one queue within a bicycle lane at the stop line. Since bicycles maintain a certain distance from the adjacent lane and the curb, the number of queues formed varies based on the width of the bicycle lane. Therefore, the saturation flow rate for a bicycle lane depends on the number of queues or the width of the bicycle lane. The saturation flow rates for bicycle lanes of varying widths are proposed on the basis of the lateral stopped distance of bicycles. Empirical evidence from intersections in Colorado and California is used to propose a new method to estimate the capacity for a bicycle lane.

Review and Evaluation of Methods for Analyzing Capacity at Signalized Intersections

1997 ◽  
Vol 1572 (1) ◽  
pp. 160-166 ◽  
Author(s):  
Catherine C. McGhee ◽  
Eugene D. Arnold
Keyword(s):  
Simulation Model ◽  
Traffic Engineering ◽  
Queue Length ◽  
Computer Programs ◽  
Signalized Intersections ◽  
Capacity Analysis ◽  
Highway Capacity ◽  
Operational Characteristics ◽  
Study Results ◽  
Departments Of Transportation

Capacity analysis is a critical activity in traffic engineering and planning divisions of state departments of transportation across the nation. The Highway Capacity Manual (HCM) provides a methodology for capacity analysis that is commonly accepted and often required by state departments of transportation. The variety of computer programs that exist to aid transportation professionals in conducting capacity analyses has led to questions regarding the best methods to use under various conditions. Several computer programs other than the Highway Capacity Software (HCS) that are commonly used in evaluating capacity at signalized intersections were evaluated to determine which ones provide acceptable results. The results obtained from a simulation model were also evaluated to determine whether the model could be used to determine the operational characteristics of signalized intersections. The study results, although based on limited data, provided valuable information about the programs evaluated. HCS, SIGNAL94, HCM/Cinema, and the simulation model TRAF-NETSIM are all acceptable for capacity analysis at isolated intersections. SIGNAL94, HCM/Cinema, and TRAF-NETSIM provide reasonable estimates of queue length at isolated intersections. However, at isolated intersections where congested, oversaturated conditions exist, TRAF-NETSIM provides more accurate measures of delay and queue length. At nonisolated intersections where queueing and spill-back are potential problems, simulation analysis with TRAF-NETSIM is recommended instead of capacity analysis to determine the operational characteristics of the corridor.

Modifying Highway Capacity Manual Methodology for Inclusion of Flashing-Yellow-Arrow Delay and Suppression

2020 ◽  
Vol 2674 (12) ◽  
pp. 233-242
Author(s):  
Daniel J. Cook
Keyword(s):  
Sensitivity Analysis ◽  
Signalized Intersections ◽  
Signalized Intersection ◽  
Effective Strategy ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Flashing Yellow Arrow ◽  
Left Turns ◽  
Yellow Arrow

Dallas phasing is an effective strategy for increasing the efficiency of protected-permissive left turns (PPLTs) at signalized intersections, without creating left-turn traps. The flashing yellow arrow (FYA) is the most widely used PPLT signal indication when Dallas phasing is utilized. The Highway Capacity Manual (HCM) signalized intersection methodology currently contains guidance on how to handle PPLTs with Dallas phasing. At intersections with the FYA indication, some agencies have been using a feature known as FYA delay, which delays the FYA indication, usually by 1 to 4 s. More recently, some agencies have also began using another feature, which suppresses the FYA when a conflicting pedestrian phase is active. The HCM does not contain guidance on how to handle FYA delay or suppression. This research proposed modifications to the HCM signalized intersection methodology to address these two FYA strategies. A sensitivity analysis was conducted to check the reasonableness of the proposed modifications. The sensitivity analysis showed that the proposed modifications are reasonable and produced the expected results.

Detailed Observations of Saturation Headways and Start-Up Lost Times

2002 ◽  
Vol 1802 (1) ◽  
pp. 44-53 ◽  
Author(s):  
Honglong Li ◽  
Panos D. Prevedouros
Keyword(s):  
Field Measurement ◽  
Queue Length ◽  
Dominant Role ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Traffic Conditions ◽  
Start Up ◽  
Lost Time ◽  
The One ◽  
Saturation Flow

The analyses conducted in this research were based on three methodologies for the field measurement of saturation headways. The first method (M1), the one on which most past studies were based, measured the characteristics of Vehicles 4 to 12 in a standing queue. M2, the method found in the Highway Capacity Manual (HCM), counted all vehicles in a standing queue, regardless of queue length. M3 included arrivals that joined the standing queue as long as vehicles were up to 140 ft from the stop line. This study focused on one approach of a high-design intersection with heavy, random arrivals. The large number of observations and the practically ideal traffic conditions enabled the acquisition of several statistically significant results on saturation flow ( s), start-up lost time (SULT), and start-up response time (SRT): ( a) when long queues are present, the typical field measurement of s based on the first 12 vehicles is an overestimate of s for through vehicles and an underestimate of s for protected left-turning vehicles; ( b) the type of movement had a more dominant role in determining s than the level of saturation (or queue length); ( c) SRT displayed a bigger variation than headways— the left-turning movement had a significantly shorter SRT than the through movement did; and ( d) much higher SULTs were estimated in this study compared with those in the HCM.

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