Geometric Design of Low-Speed Urban Streets

2000 ◽  
Vol 1701 (1) ◽  
pp. 95-103 ◽  
Author(s):  
Joseph P. Tarris ◽  
John M. Mason ◽  
Nicholas D. Antonucci
Keyword(s):  
Traffic Engineering ◽  
Research Effort ◽  
Operating Speed ◽  
Low Speed ◽  
Urban Streets ◽  
Geometric Conditions ◽  
Speed Prediction ◽  
Design Speed ◽  
Geometric Elements

A research effort is progressing to develop a rational process for designing roadway geometric elements on low-speed urban streets and using a “target”operating speed as the preselected design speed. The goal is to provide geometric street designs that reflect the in situ operating environment (form to follow function). Such an approach produces geometric conditions that result in operating speeds that are consistent with driver expectations and commensurate with the function and purpose of the roadway. The data collection methodology being used to develop a speed-prediction model between operating speed and roadway geometry, roadside features, land use, and traffic engineering considerations is also described. A comparison of design speed and operating speed for one study site is provided as an example of anticipated results.

scholarly journals Operating Speed Prediction Models for Tangent Segments: A Brief Review

2021 ◽  
Vol 7 (12) ◽  
pp. 2150-2164
Author(s):  
Musab AbuAddous
Keyword(s):  
Prediction Models ◽  
Flow Speed ◽  
Operating Speed ◽  
The Road ◽  
Traffic Characteristics ◽  
Collection Number ◽  
Speed Prediction ◽  
Study Sites ◽  
Straight Segments ◽  
Geometric Elements

This paper provides a review of studies aimed at developing operating speed prediction models for road tangent sections. The review included many studies, conducted in different geographical areas of the world, in terms of road classification, types of vehicles, techniques and devices used in data collection, number of study sites, the principle adopted in extracting the free-flow speed, as well as the topography that the road path passes through and grads of the studied sections. Moreover, this review mentioned the analysis methods adopted in the modeling, and included the model formulas that the researchers have reached in their studies, as it showed all the geometric elements and traffic characteristics that appeared in the models as independent variables. The author has avoided critiquing or evaluating the methodologies of the reviewed research and accordingly this paper has been prepared for documentation only. The author aims primarily to save the effort and time of graduate students and researchers interested in modeling the operating speed on straight segments, as all data and information are arranged in tables and coordinated for this purpose. Doi: 10.28991/cej-2021-03091784 Full Text: PDF

Analyzing Influence of Geometric Design on Operating Speeds Along Low-Speed Urban Streets: Mixed-Model Approach

2000 ◽  
Vol 1737 (1) ◽  
pp. 18-25 ◽  
Author(s):  
Christopher M. Poe ◽  
John M. Mason
Keyword(s):  
Repeated Measures ◽  
Mixed Model ◽  
Statistical Approach ◽  
Geometric Design ◽  
Operating Speed ◽  
Low Speed ◽  
Mixed Model Approach ◽  
Advantages And Disadvantages ◽  
Geometric Elements ◽  
Model Approach

Studies have documented the significant effect of horizontal curvature on operating speed on two-lane rural highways. The geometric design of these facilities emphasizes the forgiving roadside to accommodate the higher vehicular speeds. High-speed geometric design is predicated on selecting design values for geometric elements that promote speed consistency and safety. The low-speed environment has different objectives in trying to provide access and accommodate multiple roadway users, such as bicyclists and pedestrians. The goal is to maintain lower speeds and thus to achieve the functionality of the roadway and improve overall safety. Too often, the speeds on these facilities exceed the intended target speed of the roadway. A study conducted by the Pennsylvania Transportation Institute supported several research efforts in the low-speed environment. Presented is a more sophisticated analysis of low-speed urban street data using mixed models. A mixed-model statistical approach with repeated measures is used to analyze the influence of geometric elements on operating speed. The power of a mixed-model approach is that it accounts for the random effect in the database (such as the data collection sites themselves) while modeling the fixed geometric effects. Because data were collected at several points along each roadway, the analysis also applies a repeated-measures approach that addresses the geometric elements effect on the same subjects traversing a roadway. The advantages and disadvantages of applying a more sophisticated statistical approach are presented.

Predicting Operating Speeds on Low-Speed Urban Streets: Regression and Panel Analysis Approaches

1996 ◽  
Vol 1523 (1) ◽  
pp. 46-54 ◽  
Author(s):  
Joseph P. Tarris ◽  
Christopher M. Poe ◽  
John M. Mason ◽  
Konstadinos G. Goulias
Keyword(s):  
Linear Regression ◽  
Data Aggregation ◽  
Regression Models ◽  
Descriptive Statistics ◽  
Operating Speed ◽  
Panel Analysis ◽  
Ongoing Research ◽  
Variable Effect ◽  
Low Speed ◽  
Urban Streets

This study compares different statistical approaches to modeling the geometric and driver effects on operating speeds along low-speed urban streets. Linear regression on speed data obtained through data aggregation, linear regression on individual speed data, and panel analysis are discussed. Data collected from ongoing research examining operating speed on low-speed urban streets were modeled by the three techniques. The findings of the modeling techniques are compared and their influence on predicting probable operating speeds of a facility are presented. Traditionally, empirical analysis of operating speed has relied on regression models, using descriptive statistics such as 85th-percentile speed or mean speed to describe the data. This study demonstrates how the use of descriptive statistics obtained through data aggregation misleadingly reduces the total variability and nature of the variability associated with the statistical relationship. The fit of the regression function may appear to be increased, but the influence of the geometric elements may be overstated or understated. Data aggregation also affects inferential and prediction measures. Predictions from models based on aggregate data may appear to be more precise, but this does not imply that they are more reliable. Regression models of speed choice at a specific location within the roadway alignment may explain the effect of geometry but may not capture the effect of individual driver speed choice. As demonstrated in this study, the individual driver effect and geometric variable effect are important. The preliminary conclusion is that the driver's speed choice is highly dependent on roadway geometry and individual driver behavior.

Effect of speed prediction models and perceived radius on design consistency

2005 ◽  
Vol 32 (2) ◽  
pp. 388-399 ◽  
Author(s):  
Laurel Richl ◽  
Tarek Sayed
Keyword(s):  
Prediction Models ◽  
Operating Speed ◽  
The Road ◽  
Speed Prediction ◽  
The Difference ◽  
Design Speed ◽  
Design Consistency ◽  
Side Friction ◽  
Consistency Evaluation ◽  
Selection Of

The most frequently used criteria to evaluate design consistency are the difference between design speed and operating speed, operating speeds on successive elements, and assumed side friction of the road and that demanded by the driver. The operating speed, often obtained using speed prediction models, influences each design consistency criteria. There has been considerable research in developing design consistency measures and evaluation tools, but little research has been done on the influence that different speed prediction models have on design consistency criteria. In addition, there has been little research as to how design factors such as driver perception of combined horizontal and vertical curves influence speed prediction models. This paper investigates how the selection of speed prediction models and driver perception of combined horizontal and vertical curves influence design consistency evaluation. The selection of the speed prediction model has a significant impact on design consistency evaluation. The use of perceived radius, which accounts for driver perception of combined alignments, slightly influenced the outcome of the design consistency evaluation.Key words: design consistency, speed prediction models, driver perception, combined horizontal and vertical curves, perceived radius, geometric design.

scholarly journals Speed Models for Motorcycle Riders for Two-lane Rural Roads

2021 ◽  
Vol 17 ◽  
pp. 595-603
Author(s):  
Panagiotis Lemonakis ◽  
George Botzoris ◽  
Athanasios Galanis ◽  
Nikolaos Eliou
Keyword(s):  
Prediction Models ◽  
Flow Speed ◽  
Operating Speed ◽  
Rural Roads ◽  
The Road ◽  
Horizontal Curves ◽  
Road Geometry ◽  
Speed Prediction ◽  
The Subject ◽  
On The Road

The development of operating speed models has been the subject of numerous research studies in the past. Most of them present models that aim to predict free-flow speed in conjunction with the road geometry at the curved road sections considering various geometric parameters e.g., radius, length, preceding tangent, deflection angle. The developed models seldomly take into account the operating speed profiles of motorcycle riders and hence no significant efforts have been put so far to associate the geometric characteristics of a road segment with the speed behavior of motorcycle riders. The dominance of 4-wheel vehicles on the road network led the researchers to focus explicitly on the development of speed prediction models for passenger cars, vans, pickups, and trucks. However, although the motorcycle fleet represents only a small proportion of the total traffic volume motorcycle riders are over-represented in traffic accidents especially those that occur on horizontal curves. Since operating speed has been thoroughly documented as the most significant precipitating factor of vehicular accidents, the study of motorcycle rider's speed behavior approaching horizontal curves is of paramount importance. The subject of the present paper is the development of speed prediction models for motorcycle riders traveling on two-lane rural roads. The model was the result of the execution of field measurements under naturalistic conditions with the use of an instrumented motorcycle conducted by experienced motorcycle riders under different lighting conditions. The implemented methodology to determine the most efficient model evaluates a series of road geometry parameters through a comprehensive literature review excluding those with an insignificant impact to the magnitude of the operating speeds in order to establish simple and handy models.

Influence of Circumferential Inflow Distortion on the Performance of a Low Speed, High Aspect Ratio Contra Rotating Axial Fan

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Chetan Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Rotational Speed ◽  
Total Pressure ◽  
Flow Behavior ◽  
Axial Fan ◽  
Low Speed ◽  
Overall Performance ◽  
Design Speed ◽  
Inflow Conditions

The influence of circumferential inflow distorted on the performance and flow behavior of a high aspect ratio, low speed contra rotating fan is reported in this paper. The total pressure at the inlet is artificially distorted by means of 90 deg mesh sector with a porosity of 0.70. The performance of the contra rotating fan was studied under different speed combinations of the two rotors under clean and distorted inflow conditions. Detailed flow analyses were conducted under design and off-design conditions. In order to understand the effect of distortion and its extent, the distortion sector was rotated circumferentially at intervals of 15 deg to cover the entire annulus. Detailed measurements of the total pressure, velocity components, and flow angles were carried out at the inlet of the first rotor, between the two rotors, and at the exit of the second rotor. The study reveals a few interesting aspects on the effect of inflow distortion on the performance of a contra-rotating stage. For the design speed combination and lower rotational speed of rotor-2, a reduction in the overall operating range with a shift of the peak pressure point towards higher mass flow rate, was observed. It is observed that the effect of inflow distortion at the inlet of rotor-1 gets transferred in the direction of rotor-1 rotation and spreads across the entire annulus. The opposite sense of rotation of rotor-2 causes the distortion effect to get transferred in the direction of rotation of rotor-2 with an associated reduction in the total pressure near the hub. It is observed that a higher rotational speed of the second rotor has a beneficial effect on the overall performance due to the strong suction by generated higher rotational speed of rotor-2.

Obstruction Influence on Low-Speed, In-Situ Stratospheric Turbulence Measurements

2021 ◽  
Author(s):  
Joseph L. Pointer ◽  
Kenneth E. Jansen ◽  
Brian M. Argrow ◽  
Dale A. Lawrence
Keyword(s):  
Turbulence Measurements ◽  
Low Speed

scholarly journals In-situ severe breeding habitat intervention only achieves temporary success in reducing Batrachochytrium dendrobatidis infection

2020 ◽  
Vol 41 (2) ◽  
pp. 261-267 ◽  
Author(s):  
Andrés Fernández-Loras ◽  
Luz Boyero ◽  
Jaime Bosch
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Research Effort ◽  
Breeding Habitat ◽  
Habitat Manipulation ◽  
Breeding Sites ◽  
Breeding Habitats ◽  
The Common ◽  
Natural Breeding ◽  
Midwife Toad

Abstract Chytridiomycosis, an emerging infectious disease caused by the fungus Batrachochytrium dendrobatidis (Bd), is causing sharp declines in amphibian populations around the globe. A substantial research effort has been made to study the disease, including treatments against Bd, but most treatments have been applied to captive amphibians only. We report a study aimed at clearing wild populations of the Common Midwife toad Alytes obstetricans. We removed all larvae from natural breeding sites (cattle troughs) and conducted two types of severe breeding habitat manipulation (complete drying and fencing for the whole breeding season). While larval removal followed by drying was a successful method of Bd elimination, the effect was only temporary. Since terrestrial habits of adult A. obstetricans prevent them from infection, our findings suggest that, even in simple breeding habitats where all aquatic amphibian stages can be handled and extreme habitat intervention is possible, Bd cannot be eliminated without controlling other potential Bd reservoirs in the surroundings of breeding sites.

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