Evaluating the Effect of Incidents on Freeway Facilities and Updating the Incident Capacity Adjustments for HCM

2020 ◽  
pp. 036119812094953
Author(s):  
Jeremy Addison ◽  
Seyedbehzad Aghdashi ◽  
Nagui M. Rouphail
Keyword(s):  
Calibration Method ◽  
Time Dependent ◽  
Optimal Time ◽  
Incident Management ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Management Actions ◽  
Look Up Table ◽  
Adjustment Factors ◽  
Over Time

This paper investigates the effect of incidents on freeway segment capacity. Currently, the Highway Capacity Manual (HCM) provides a look-up table linking the remaining segment capacity fraction during an incident to the total and closed number of lanes on the segment. In reality, segment capacity during an incident will tend to vary over time, with the most severe effects felt early on before any type of response is initiated, with congestion progressively improving as the appropriate incident management actions are implemented. By applying a genetic algorithm calibration method on each incident day and calibrating the incident capacity adjustment factors (CAFs), optimal time-dependent CAFs were derived that best represented the effect of incidents on the freeway segment capacity. By analyzing the optimal CAFs, the strongest relationship was revealed to be between the optimal time-dependent CAF and the temporal progression of the incident. A regression model was developed to represent this behavior. This was formulated in a manner that can directly adjust the current HCM’s fixed CAF values (for a specific lane closure configuration) for modeling incidents both in single day, seed file application, or for an entire year reliability analysis. A portion of WB I-540 in Raleigh, NC was selected as the study area in which the proposed method was tested. Between January 2014 and December 2018, the team identified 22 isolated incidents (away from the recurring congestion period) that closed one or two lanes of traffic, creating a distinct congestion pattern.

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.

Evaluating the Operational Effect of Narrow Lanes and Shoulders for the Highway Capacity Manual

2019 ◽  
Vol 2673 (10) ◽  
pp. 558-570 ◽  
Author(s):  
Alexandra Kondyli ◽  
David K. Hale ◽  
Mohamadamin Asgharzadeh ◽  
Bastian Schroeder ◽  
Anxi Jia ◽  
...  
Keyword(s):  
Traffic Congestion ◽  
Flow Speed ◽  
Mitigation Strategies ◽  
Analytical Models ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Lane Width ◽  
Adjustment Factors ◽  
Manual Methods ◽  
Width Reduction

Unnecessary traffic delays and vehicle emissions have adverse effects on quality of life. To solve the traffic congestion problem in the U.S.A., mitigation or elimination of bottlenecks is a top priority. Agencies across the U.S.A. have deployed several congestion mitigation strategies, such as lane and shoulder width reduction, which aim to adding lanes without significantly altering the footprint of the freeway. A limited number of studies have evaluated the operational benefits of lane narrowing. Although the Highway Capacity Manual does account for lane and shoulder widths, the adjustments that it provides are outdated. The goal of this research was to develop analytical models, compatible with the Highway Capacity Manual methods, to account for lane and shoulder width narrowing, using field data from across the U.S.A. This paper presents a new free-flow speed regression model, which accounts for lane and shoulder widths, and capacity adjustment factors depending on the lane width.

Determining the capacity of the Canadian trans-mountain highway system

1976 ◽  
Vol 3 (3) ◽  
pp. 355-371
Author(s):  
John F. Morrall ◽  
Neville Cameron ◽  
Al Werner
Keyword(s):  
Highway Capacity ◽  
Passenger Car ◽  
Highway Capacity Manual ◽  
Recreational Vehicles ◽  
Improper Use ◽  
Adjustment Factors ◽  
Highway Planning ◽  
Design Hourly Volume ◽  
Selection Of

Trans-mountain highway capacity is sensitive to the percentage of recreational vehicles in the traffic stream, the manner in which passenger car equivalents for recreational vehicles are used in capacity computations, terrain classification, and the choice of design hourly volume. The sensitivity of capacity to these factors is demonstrated for the trans-mountain portion of the Trans-Canada highway which is a two-lane highway, characterized in many locations by long steep grades. This particular highway has a high percentage of recreational vehicles during summer months. The Highway Capacity Manual does not make any provision for the effect of such vehicles and previous highway planning studies have used the adjustment factors for trucks and buses to estimate their effect. Neglecting the effect of recreational vehicles and/or improper use of their passenger car equivalents in capacity computations can result in serious errors in the determination of highway capacity especially in mountainous areas. Further research is required in the areas of terrain definition, selection of design hourly volume, and the present concept of level of service.

Freeway Facility Methodology in Highway Capacity Manual 2000

2000 ◽  
Vol 1710 (1) ◽  
pp. 171-180 ◽  
Author(s):  
Brian S. Eads ◽  
Nagui M. Rouphail ◽  
Adolf D. May ◽  
Fred Hall
Keyword(s):  
Intelligent Transportation System ◽  
Simulation Models ◽  
Companion Paper ◽  
Ramp Metering ◽  
Incident Management ◽  
Highway Capacity ◽  
Time Intervals ◽  
Highway Capacity Manual ◽  
Traffic Conditions ◽  
First Time

The next edition of the Highway Capacity Manual (HCM 2000) will contain for the first time an operational analysis procedure for directional freeway facilities up to 20 to 25 km long. At the simplest level, this procedure integrates the proposed HCM 2000 methods for the analysis of basic, ramp, and weaving segments to enable the analysis of an entire facility. But the proposed facility methodology goes much further. It allows the user to analyze multiple, contiguous time intervals with timevarying demands and capacities. It can handle both undersaturated and oversaturated traffic conditions (with some limitations). In the latter case, both the spatial and time extent of congestion are estimated. Finally, the method permits the investigation of the effect of many traditional and intelligent transportation system–based freeway improvement strategies such as full or auxiliary lane additions, ramp metering, incident management, and a limited set of high-occupancy-vehicle designs on facility performance. Described here is the conceptual model for and computational steps of the methodology, with emphasis on the components for analysis of oversaturated conditions. The scope and limitations of the methods are also highlighted. Reference is given to a companion paper that describes how the results of the method were validated in the field and how they compared with those obtained from widely used freeway simulation models.

Utilization of Auxiliary Through Lanes at Intersections of Four-Lane, Two-Way Roadways

2000 ◽  
Vol 1737 (1) ◽  
pp. 26-33 ◽  
Author(s):  
Mohammed S. Tarawneh
Keyword(s):  
Group Delay ◽  
Signalized Intersections ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Level Of Use ◽  
Adjustment Factors ◽  
Limited Length ◽  
Auxiliary Lanes ◽  
Auxiliary Through Lanes ◽  
Lane Utilization

To increase the capacity of through traffic at signalized intersections, additional lanes with limited length—called auxiliary lanes—are added to the roadway at the intersection. Because of their limited length, as well as other factors, these lanes are not as fully utilized as other continuous through lanes. Research was undertaken with two objectives: ( a) to observe and identify the level of use of auxiliary through lanes added at intersections of four-lane, two-way roadways; and ( b) to study the effects of auxiliary lane length, right-turn volume, and through/right-turn lane group delay on the level of their use. Lane-use data collected during 1,050 saturated cycles at eight signalized intersections with different auxiliary lane lengths were used to accomplish research objectives. All factors investigated—auxiliary lane length, right-turn volume, and stopped-delay—were found to contribute significantly to the use of auxiliary lanes at 0.01 level. The level of each factor’s contribution, however, was dependent on the level of the other two. Lane use of nearly one to seven straight-through vehicles per cycle, depending on levels of factors investigated, was observed at the study locations. Longer auxiliary lanes, lower right-turn volumes, and excessive approach delays encouraged the use of auxiliary lanes by straight-through vehicles. The range of lane utilization adjustment factors ( fLU-factors) calculated from field data was 0.73 to 0.82, which is lower than the 1997 Highway Capacity Manual default value of 0.91 for a three-lane through/right-turn group.

Time course of meiotic spindle development in MII oocytes

Zygote ◽  
2010 ◽  
Vol 19 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Suha Kilani ◽  
Simon Cooke ◽  
Michael Chapman
Keyword(s):  
Time Course ◽  
Polarized Light ◽  
Time Dependent ◽  
Meiotic Spindle ◽  
Optimal Time ◽  
Stimulation Protocol ◽  
Time Intervals ◽  
Spindle Development ◽  
Microscopy Images ◽  
Over Time

SummaryThe aim of this study was to examine changes in meiotic spindle morphology over time to potentially optimize timing for ICSI. Using polarized light microscopy, images of MII oocytes were captured after retrieval of oocytes in stimulated cycles at six time intervals in culture: 36–36.5 h, 36.5–37.0 h, 38–38.5 h, 39–39.5 h, 40–40.5 h and 40.5–41 h post hCG. Captured images were analysed for spindle presence and their retardance. Results showed that spindles were detected in 58% (45/78) of oocytes at 36–36.5 h. This percentage rose to a peak (96% vs. 58%, p < 0.001) at 39–39.5 h and stabilized between 39–40.5 h post trigger then significantly declined at 40.5–41 h post hCG (96% vs. 77%, p < 0.001). Average spindle retardance increased from 36–36.5 h (1.8 ± 0.7 nm) until it peaked at 39–40.5 h (3.8 ± 0.8 nm, p < 0.0001) and then declined significantly after 40.5–41 h (3.2 ± 0.9 nm, p = 0.0001). These results show that the meiotic spindle appearance is time dependent with the majority of oocytes having detectable spindles and highest retardance between 39–40.5 h post hCG under currently used stimulation protocol after which they start to disaggregate. 39–40.5 h post hCG may be the optimal time for ICSI.

Vehicular Flow Past Incidents Involving Lane Blockage on Urban Roads: A Preliminary Exploration

1998 ◽  
Vol 1634 (1) ◽  
pp. 86-92 ◽  
Author(s):  
Richard A. Raub ◽  
Ronald C. Pfefer
Keyword(s):  
Limited Attention ◽  
Incident Management ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Capacity Reduction ◽  
Case Rate ◽  
The Mean ◽  
Mean Differences ◽  
Initial Results ◽  
Urban Arterial

The effects of freeway lane reductions on roadway capacity have been discussed in the literature, but only limited attention has been given to capacity reduction on urban arterial roadways. Videotaping of incident management on arterial roadways as part of another project made available data that could be measured and converted into headways. Fifteen incidents involving crashes and disabled vehicles from which measurements were drawn are examined in this report. All events blocked one lane on a four-lane urban arterial. From the data, headways were measured and estimates of vehicle flow rates computed. Overall, an incident blocking one of two lanes on an urban roadway will reduce the idealized flow from the 1,900 vehicles per hour per lane (3,800 vehicles per hour) as suggested in the Highway Capacity Manual by more than 60 percent for crashes and more than 50 percent for disabled vehicles. Crashes resulting in personal injury had a worse-case rate of 1,230 vehicles per hour, or 32 percent of capacity. The lowest recorded flow rate for disabled vehicles was 1,650 vehicles per hour, or 43 percent of capacity. Distribution of headways around crashes were substantially skewed. On the other hand, headways for disabled vehicles tended to cluster around the mean. Differences in headways not only arose from the type of incident but also appeared to be related to the amount of responder activity (e.g., one police officer versus multiple public safety responders) and by the cross-section of the roadway. In the latter case, roadways with painted medians had shorter headways than those with raised medians or painted center lines. More observations need to be made to validate these initial results.

scholarly journals An Analysis of the Interactions between Adjustment Factors of Saturation Flow Rates at Signalized Intersections

2020 ◽  
Vol 12 (2) ◽  
pp. 665 ◽  
Author(s):  
Yi Wang ◽  
Jian Rong ◽  
Chenjing Zhou ◽  
Xin Chang ◽  
Siyang Liu
Keyword(s):  
Traffic Congestion ◽  
National Standard ◽  
Percentage Error ◽  
Heavy Vehicles ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Lane Width ◽  
Adjustment Factors ◽  
Saturation Flow

An insufficient functional relationship between adjustment factors and saturation flow rate (SFR) in the U.S. Highway Capacity Manual (HCM) method increases an additional prediction bias. The error of SFR predictions can reach 8–10%. To solve this problem, this paper proposes a comprehensive adjusted method that considers the effects of interactions between factors. Based on the data from 35 through lanes in Beijing and 25 shared through and left-turn lanes in Washington, DC, the interactions between lane width and percentage of heavy vehicles and proportion of left-turning vehicles were analyzed. Two comprehensive adjustment factor models were established and tested. The mean absolute percentage error (MAPE) of model 1 (considering the interaction between lane width and percentage of heavy vehicles) was 4.89% smaller than the MAPE of Chinese National Standard method (Standard Number is GB50647) at 13.64%. The MAPE of model 2 (considering the interaction between lane width and proportion of left-turning vehicles was 33.16% smaller than the MAPE of HCM method at 14.56%. This method could improve the accuracy of SFR prediction, provide support for traffic operation measures, alleviate the traffic congestion, and improve sustainable development of cities.

Effect of Pedestrians on Capacity of Signalized Intersections

1998 ◽  
Vol 1646 (1) ◽  
pp. 37-46 ◽  
Author(s):  
Joseph S. Milazzo ◽  
Nagui M. Rouphail ◽  
Joseph E. Hummer ◽  
D. Patrick Allen
Keyword(s):  
Signalized Intersections ◽  
Geometric Constraints ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Flow Adjustment ◽  
Conflict Zone ◽  
Adjustment Factors ◽  
Left And Right ◽  
Saturation Flow ◽  
Green Period

In Chapter 9 of the 1994 update to the 1985 Highway Capacity Manual, the operational and planning analysis of signalized intersections is discussed. The methodology for saturation flow rate estimation does not consider all elements of the interaction between pedestrians and turning vehicles. This study describes this interaction for left and right turns using a conflict-zone-occupancy approach. A conflict zone is a portion of an intersection, typically in the crosswalk, in which pedestrians and vehicles compete for space. Conflict-zone occupancy, defined as the fraction of the effective green period during which pedestrians occupy a conflict zone, provides the basis for a rational adjustment to saturation flow. This study details the results of a multiregional data collection effort that confirms the validity of the conflict-zone-occupancy approach. In addition, this study describes the effect of geometric constraints, as reflected in the number of receiving lanes versus the number of turning lanes, on turning-vehicle saturation flow. After consideration of signalized intersection phasing and turn protection, one can calculate saturation flow adjustment factors reflecting the effect of pedestrians on lane groups containing vehicles turning left ( fLpb) or right ( fRpb).

Developing Highway Capacity Manual Capacity Adjustment Factors for Connected and Automated Traffic on Freeway Segments

2020 ◽  
Vol 2674 (10) ◽  
pp. 401-415
Author(s):  
Adekunle Adebisi ◽  
Yan Liu ◽  
Bastian Schroeder ◽  
Jiaqi Ma ◽  
Burak Cesme ◽  
...  
Keyword(s):  
Transportation Systems ◽  
Market Penetration ◽  
Cruise Control ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Traffic Characteristics ◽  
Cooperative Adaptive Cruise Control ◽  
Human Driver ◽  
The Future ◽  
Adjustment Factors

Connected and automated vehicles (CAVs) will undoubtedly transform many aspects of transportation systems in the future. In the meantime, transportation agencies must make investment and policy decisions to address the future needs of the transportation system. This research provides much-needed guidance for agencies about planning-level capacities in a CAV future and quantify Highway Capacity Manual (HCM) capacities as a function of CAV penetration rates and vehicle behaviors such as car-following, lane change, and merge. As a result of numerous uncertainties on CAV implementation policies, the study considers many scenarios including variations in parameters (including CAV gap/headway settings), roadway geometry, and traffic characteristics. More specifically, this study considers basic freeway, freeway merge, and freeway weaving segments in which various simulation scenarios are evaluated using two major CAV applications: cooperative adaptive cruise control and advanced merging. Data from microscopic traffic simulation are collected to develop capacity adjustment factors for CAVs. Results show that the existence of CAVs in the traffic stream can significantly enhance the roadway capacity (by as much as 35% to 40% under certain cases), not only on basic freeways but also on merge and weaving segments, as the CAV market penetration rate increases. The human driver behavior of baseline traffic also affects the capacity benefits, particularly at lower CAV market penetration rates. Finally, tables of capacity adjustment factors and corresponding regression models are developed for HCM implementation of the results of this study.

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