Improved Speed-Flow Relationships for Planning Applications

1997 ◽  
Vol 1572 (1) ◽  
pp. 18-23 ◽  
Author(s):  
Alexander Skabardonis ◽  
Richard Dowling
Keyword(s):  
Field Data ◽  
Air Pollutant ◽  
Pollutant Emissions ◽  
Speed Estimation ◽  
Highway Capacity ◽  
Estimation Techniques ◽  
Highway Capacity Manual ◽  
Planning Models ◽  
Speed Flow ◽  
Simulation Results

Improved speed-estimation techniques for planning applications were developed and tested. Comparisons with field data and simulation results indicate that the recommended techniques provide better accuracy and consistency with the procedures contained in the 1994 update of the Highway Capacity Manual. These speed-estimation techniques will improve the accuracy of long-range transportation planning models for predicting travel time, delay, and air-pollutant emissions.

Predicting Lane-by-Lane Flows and Speeds for Freeway Segments

2020 ◽  
Vol 2674 (9) ◽  
pp. 1052-1068
Author(s):  
Fabio Sasahara ◽  
Luan Guilherme Staichak Carvalho ◽  
Tanay Datta Chowdhury ◽  
Zachary Jerome ◽  
Lily Elefteriadou ◽  
...  
Keyword(s):  
Field Data ◽  
Performance Estimation ◽  
Free Flow ◽  
Highway Capacity ◽  
Distribution Models ◽  
Highway Capacity Manual ◽  
Speed Flow ◽  
Flow Speeds ◽  
The Relationship

The Highway Capacity Manual is a major reference for evaluating the capacity and quality of service of road facilities. However, it holds the assumption that lanes perform equally, which can result in inaccuracies in performance estimation. The main purpose of this research is to develop a series of models for estimating flows and speeds by lane for various types of freeway segments, including basic, merge, and diverge types. These models consider the demand-to-capacity ratio, the presence of trucks, grade, and the presence of upstream and downstream ramps. To predict lane performance effectively, it is critical that capacity and free-flow speeds are also determined for individual lanes. Therefore, this study also investigates the relationship between segment average values and lane values for free-flow speeds and capacities, and proposes a method to estimate these parameters for each lane as a function of the segment average. Observed field data has shown that free-flow speeds and capacities have lowest values on the shoulder lanes and highest values on the median lanes. Speed and flow data were collected from 48 segments throughout the U.S.A., including basic, merge, and diverge segments, to develop flow and speed distribution models. A case example is provided to illustrate the application of the developed model and the predicted speed–flow relationship is compared with field data, with satisfactory results.

Validation Results for Four Models of Oversaturated Freeway Facilities

2000 ◽  
Vol 1710 (1) ◽  
pp. 161-170 ◽  
Author(s):  
Fred L. Hall ◽  
Loren Bloomberg ◽  
Nagui M. Rouphail ◽  
Brian Eads ◽  
Adolf D. May
Keyword(s):  
Field Data ◽  
Simulation Models ◽  
Highway Capacity ◽  
Highway Capacity Manual

Some researchers have noted that the current procedures in the Highway Capacity Manual (HCM) may not be appropriate for analyzing complex or oversaturated freeway facilities. The results of a comparison of an HCM-based procedure with field data from six such freeway sites are reported. Because simulation has often been suggested as an alternative to the HCM for oversaturated freeway facilities, three simulation models (CORSIM, FREQ, and INTEGRATION) were also used to analyze these same six sites. The results suggest that the HCM-based procedures do as well as the three simulation models in reproducing the average speeds across the freeway facilities.

Validation of Generalized Delay Model for Vehicle-Actuated Traffic Signals

1997 ◽  
Vol 1572 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Nagui M. Rouphail ◽  
Mohammad Anwar ◽  
Daniel B. Fambro ◽  
Paul Sloup ◽  
Cesar E. Perez
Keyword(s):  
North Carolina ◽  
Field Data ◽  
Traffic Signals ◽  
Signalized Intersections ◽  
Delay Model ◽  
Highway Capacity ◽  
Generalized Model ◽  
Highway Capacity Manual ◽  
Traffic Volumes ◽  
Isolated Intersection

One limitation of the Highway Capacity Manual (HCM) model for estimating delay at signalized intersections is its inadequate treatment of vehicle-actuated traffic signals. For example, the current delay model uses a single adjustment for all types of actuated control and is not sensitive to changes in actuated controller settings. The objective in this paper was to use TRAF-NETSIM and field data to evaluate a generalized delay model developed to overcome some of these deficiencies. NETSIM was used to estimate delay at an isolated intersection under actuated control, and the delay values obtained from NETSIM were then compared with those estimated by the generalized delay model. In addition, field data were collected from sites in North Carolina, and delays observed in the field were compared with those estimated by the generalized delay model. The delays estimated by the generalized model were comparable with the delays estimated by NETSIM. The data compared favorably for degrees of saturation of less than 0.8. However, at higher degrees of saturation, the generalized model produced delays that were higher than NETSIM’s. Some possible explanations for this discrepancy are discussed. The delays estimated by the generalized model were comparable with delays observed in the field. Researchers have concluded that the generalized delay model is sensitive to changes in traffic volumes and vehicle-actuated controller settings and that the generalized delay model is much improved over the current HCM model in estimating delay at vehicle-actuated traffic signals.

Study of Speed-Flow Relationships on Individual Freeway Lanes

1997 ◽  
Vol 1591 (1) ◽  
pp. 7-13 ◽  
Author(s):  
V. F. Hurdle ◽  
Mark I. Merlo ◽  
Doug Robertson
Keyword(s):  
Practical Interest ◽  
Linear Functions ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Speed Flow ◽  
High Flows ◽  
The Mean ◽  
The Individual ◽  
The Relationship ◽  
Very High

Many researchers have examined the form of the relationship between speed and flow on freeways. However, these researchers have concentrated on relationships for the freeway as a whole instead of on individual lanes. In this study, the relationship was examined for each of the three lanes at two locations on Highway 401 in metropolitan Toronto. It proved possible to accurately describe the mean speed in each lane with simple linear functions over the range of flows of most practical interest. Cubic functions provided comparable results over a wider range of flows, but it appears unlikely that the very high and very low flows are of sufficient interest to justify the added complexity. When an attempt was made to examine the relationship between speed and flow for the entire roadway, the linear functions were not adequate, but cubic functions performed reasonably well. However, the details of the full roadway curves are quite different from those of the curves described in the 1994 Highway Capacity Manual. In particular, the curves described in the manual are much steeper than the Highway 401 curves at high flows, implying a much more rapid loss of performance as flow approaches capacity than was observed. The full roadway curves are also surprisingly different from the curves for the individual lanes.

Lane-by-Lane Analysis Framework for Conducting Highway Capacity Analyses at Freeway Segments

2019 ◽  
Vol 2673 (8) ◽  
pp. 523-535
Author(s):  
Fabio Sasahara ◽  
Lily Elefteriadou ◽  
Shen Dong
Keyword(s):  
Flow Distribution ◽  
Time Of Day ◽  
Heavy Vehicles ◽  
Highway Capacity ◽  
Operational Conditions ◽  
Highway Capacity Manual ◽  
Loop Detectors ◽  
Speed Flow ◽  
Flow Speeds ◽  
The Usa

The Highway Capacity Manual (HCM) methodology for freeway systems yields average speed values for each segment and does not consider lane-by-lane flow and operational conditions. However, flows are not equally distributed between lanes. In congested conditions and particularly when spillback occurs, flows and traffic conditions vary widely. For example, the rightmost lane may be blocked while the leftmost lane is free-flowing. The purpose of this research is to develop a model for estimating lane-by-lane speeds and flows under various freeway designs and demands. Speed and flow data from loop detectors at several locations around the USA were collected, totaling 531,000 observations aggregated in 15-min intervals. The results show that lane flow distribution is highly dependent on the segment total flow, with different patterns for 4-, 6-, and 8-lane segments. The percentage of heavy vehicles, presence of nearby ramps, day of week, and time of day also affect the distribution of flow among freeway lanes. Theoretical lane-by-lane speed-flow curves were developed and the results were compared with field data. Results showed that lane-by-lane speeds can be estimated accurately, as long as inputs for capacity and free-flow speeds can be provided for each lane in the segment.

Accounting for Nonrandom Arrivals in Estimate of Delay at Signalized Intersections

1996 ◽  
Vol 1555 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Janice Daniel ◽  
Daniel B. Fambro ◽  
Nagui M. Rouphail
Keyword(s):  
Field Data ◽  
Empirical Studies ◽  
Primary Objective ◽  
Signalized Intersections ◽  
Degree Of Saturation ◽  
Delay Model ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Research Show

The primary objective of this research was to determine the effect of nonrandom or platoon arrivals on the estimate of delay at signalized intersections. The delay model used in the 1994 Highway Capacity Manual (HCM) accounts for nonrandom arrivals through the variable m, which can be shown to be equal to 8kI, where k describes the arrival and service distributions at the intersection and I describes the variation in arrivals due to the upstream intersection. The 1994 HCM delay model m-values are a function of the arrival type, where the arrival type describes the quality of progression at the intersection. Although an improvement to the fixed k I-value used in the 1985 delay model, the 1994 m values are based on empirical studies from limited field data and do not account for the decrease in random arrivals as the volume approaches capacity at the downstream intersection. This research provides an estimate of the variable kI for arterial conditions. An analytical equation was developed as a function of the degree of saturation, and a separate equation was developed for each signal controller type. The results from this research show that the proposed kI's provide delay estimates closer to the measured delay compared with the delay estimates using the kI-values in the 1994 HCM delay model.

Lane Utilization Model Development for Diverging Diamond Interchanges

2017 ◽  
Vol 2618 (1) ◽  
pp. 27-37
Author(s):  
Chunho Yeom ◽  
Bastian J. Schroeder ◽  
Christopher Cunningham ◽  
Katy Salamati ◽  
Nagui M. Rouphail
Keyword(s):  
United States ◽  
Field Data ◽  
Model Development ◽  
The United States ◽  
Highway Capacity ◽  
Double Crossover ◽  
Highway Capacity Manual ◽  
Diamond Interchanges ◽  
Lane Utilization ◽  
Analysis Models

The diverging diamond interchange (DDI), also known as the double crossover diamond interchange, has been a successful, if unconventional, solution used in many parts of the United States ever since its first installation in Springfield, Missouri, in June 2009. One of the challenges to agencies in planning and operating DDIs is to apply to them methodologies developed for a conventional diamond interchange. The Highway Capacity Manual 2010 (HCM 2010) provides lane use analysis models for various lane configurations. However, there is no guarantee that these models will work for DDIs. For this reason, 11 DDIs were studied nationwide ( a) to examine whether the current HCM lane use models provided accurate results for DDIs and ( b) to develop new lane use models for them if the HCM models did not work. As a result of the study, unique multiregime lane utilization models were proposed, separated by the number of approach lanes and validated by field data not used in the model development.

Field Evaluation of Highway Capacity Manual 2000 Analysis Procedures for Two-Lane Highways

2002 ◽  
Vol 1802 (1) ◽  
pp. 125-132 ◽  
Author(s):  
Michael P. Dixon ◽  
Satya Sai Kumar Sarepali ◽  
Kevin Allen Young
Keyword(s):  
Simulation Model ◽  
Field Data ◽  
Field Evaluation ◽  
Analysis Procedure ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Percent Time ◽  
Percent Time Spent Following ◽  
Northern Idaho ◽  
Rural Highway

Highway Capacity Manual (HCM) 2000 two-lane rural highway directional, two-way, and passing-lane analysis procedures based on field data and simulation were evaluated. Detailed field data were collected from two highway sections in northern Idaho, one with and one without passing lanes. The TWOPAS simulation model was used to provide additional insights. Particular attention was given to the differences in estimates for percent time spent following (PTSF) produced by the twoway and directional analysis procedures. It was found that the two-way analysis procedure was more accurate, although both procedures produced estimates that were too high. The passing-lane analysis procedure was also evaluated, and the HCM 2000 procedure was found to be conservative in its estimates of PTSF reductions due to a passing lane.

Development of an Oversaturated Speed–Flow Model Based on the Highway Capacity Manual

2013 ◽  
Vol 2395 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Yilun Xu ◽  
Billy M. Williams ◽  
Nagui M. Rouphail ◽  
R. Thomas Chase
Keyword(s):  
Flow Model ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Model Based ◽  
Speed Flow

Development of Maximum Weaving Length Model Based on HCM 2016

2020 ◽  
pp. 036119812097366
Author(s):  
Ali Kashani ◽  
Behrooz Shirgir
Keyword(s):  
Field Data ◽  
Volume Ratio ◽  
Geometric Parameters ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Traffic Conditions ◽  
Traffic Volumes ◽  
Key Features ◽  
Using Data ◽  
New Variables

Weaving segments are among the most important segments in any kind of facility. One of their key features is their maximum length (Lwmax), which determines the performance of the facility as a weaving or separate merge and diverge segments. Based on an equation in the Highway Capacity Manual (HCM 2016), only two variables VR (volume ratio) and Nwl (number of weaving lanes) influence this length. However, certain cases can be found in which traffic conditions are different but Nwl and VR values are equal. In this study, three separate weaving segments in Tehran, Iran were used and their data were collected to further analyze the influence of the traffic parameters. Calibration of field data was performed using GEH values of freeways and ramps for simulation and field traffic volumes. The simulation was therefore used on the basis of different traffic and geometric parameters, and the effects of these parameters on Lwmax were carefully observed. There were 184 simulated scenarios in Aimsun using data collected from the three weaving segments in Tehran plus simulation. In these scenarios, two geometric parameters (Nwl and Lwmax) and four traffic parameters were considered variable. It was found that for Nwl = 2 the accepted regression model containing three new variables has an R2 value equal to 0.95, and for Nwl = 3 two of the three variables were used for the model produced with an R2 value equal to 0.7.

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