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 Empirical Speed Behavior on Horizontal Ramp Curves in Interchanges in the Netherlands

2017 ◽  
Vol 2618 (1) ◽  
pp. 38-47 ◽  
Author(s):  
Haneen Farah ◽  
Aries van Beinum ◽  
Winnie Daamen
Keyword(s):  
The Netherlands ◽  
Prediction Models ◽  
Operating Speed ◽  
Trajectory Data ◽  
Design Elements ◽  
The Road ◽  
Road Design ◽  
Speed Prediction ◽  
Design Consistency ◽  
High Level

Several studies in the literature have indicated that interchanges are the most crash-prone areas within the motorway system in number and severity of accidents. The reason is the high level of turbulence as a result of vehicle lane changes and speed variability. To understand the safety consequences of an interchange design (e.g., type of connecting ramps, radii and superelevation of curves, and lane and shoulder widths), an in-depth investigation of driving speed behavior is needed. Such an investigation requires the collection of detailed trajectory data on vehicles on different interchanges. These types of data are rarely available, and as a result, such studies are scarce in the literature. The main objective of this present study was to analyze driver speed behavior on different ramps at interchanges, and to develop an operating speed prediction model as a function of the road design elements. Trajectory data on free-moving vehicles were derived from stabilized video images taken from a camera mounted underneath a helicopter, which hovered over the road areas studied. Data were collected from 29 curves at six freeway–freeway interchanges in the Netherlands. The sample included nine direct connections, 12 semidirect connections, and eight indirect connections. The findings showed that speeds were affected by several road geometric characteristics of the curves, by driver expectancy and design consistency, and by the percentage of trucks in traffic. The operating speed prediction models developed in the study will provide designers with tools to estimate the operating speed during the design process.

Operating Speed Models for Tangent Segments on Urban Roads

2017 ◽  
Vol 2618 (1) ◽  
pp. 91-99 ◽  
Author(s):  
Avi Thiessen ◽  
Karim El-Basyouny ◽  
Suliman Gargoum
Keyword(s):  
Prediction Models ◽  
Operating Speed ◽  
Critical Research ◽  
Rural Roads ◽  
Research Issues ◽  
The Road ◽  
Speed Prediction ◽  
Design Consistency ◽  
The Impact ◽  
The City

Information about operating speeds is essential to design better roads, model traffic emissions, and ensure design consistency while efficient and safe operations on roads are maintained. Therefore, understanding how different factors affect operating speeds and developing operating speed prediction models are critical research issues. Many studies have developed such models on rural roads and highways, but only a few studies have considered development of such models on urban roads and fewer still on tangential segments. This present study attempted to address these limitations by developing operating speed models with data from 249 tangential road segments in the city of Edmonton, Alberta, Canada. A generalized linear model was developed with panel data, and the primary aim was to explore the relationships between operating speeds on urban roads and features of the road environment. To study the impact of road elements on different road types, three models were created: one that combined arterial and collector locations, one for arterials only, and one for collector roads only. The results revealed that roads with sidewalks that were farther away from the road and with low object density or tree density were all associated with higher operating speeds. Locations with monolithic walks on both sides of the road had lower operating speeds. Furthermore, operating speeds decreased as access increased, while longer roads had higher operating speeds. One major takeaway was that the elements differed between road classes. The two variables, which stood out in that respect, were medians and bus stops.

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.

scholarly journals Evaluation of design consistency on horizontal curves for two-lane state roads in terms of vehicle path radius and speed

2016 ◽  
Vol 11 (2) ◽  
pp. 127-135
Author(s):  
Biljana Maljković ◽  
Dražen Cvitanić
Keyword(s):  
Horizontal Curves ◽  
Percentage Difference ◽  
Friction Factors ◽  
The Difference ◽  
Design Speed ◽  
Vehicle Path ◽  
Design Consistency ◽  
Side Friction ◽  
Curve Radius ◽  
The Impact

Experimental investigation was conducted on a 24 km long segment of the two-lane state road to collect the driver behavior data. The research involved 20 drivers driving their own cars equipped with the GPS device. Considering the impact of path radius and speed on the side friction demand, the design consistency on horizontal curves was evaluated by determining the margins of safety. The analysis showed that the vehicle path radii were mainly smaller than curve radius, on average for 12%. Regression analysis indicated that the percentage difference between the curve radius and vehicle path radius is not affected by the speed, speed differential and geometric characteristics of the curve and surrounding elements. Two different margins of safety were analyzed. One is the difference between maximum permissible side friction (based on design speed) and side friction demand, while another is the difference between side friction supply (based on operating speed) and side friction demand. Generally, demands exceeded supply side friction factors on curves with radii smaller than 150 m, whereas “poor” conditions (in terms of Lamm’s consistency levels) were noted for curves under approximately 220 m. Both values are very close to the critical radius below which higher accident rates were observed according to several accident studies. Based on the results of the research, it is proposed to use a 12% smaller curve radius for the evaluation of margin of safety and that curves with radii smaller than 200 m should be avoided on two-lane state roads outside the built-up area.

scholarly journals KELIO TRASOS HORIZONTALIŲJŲ KREIVIŲ ĮTAKA TRANSPORTO SRAUTO GREIČIUI / INFLUENCE OF ROAD ALIGNMENT HORIZONTAL CURVE ON TRANSPORT FLOW OPERATING SPEED

2019 ◽  
Vol 11 (0) ◽  
pp. 1-7
Author(s):  
Mindaugas Šeporaitis ◽  
Viktoras Vorobjovas
Keyword(s):  
Road Network ◽  
Operating Speed ◽  
Horizontal Curve ◽  
The Road ◽  
Horizontal Curves ◽  
Legal Documents ◽  
Transport Flow ◽  
Design Speed ◽  
Side Friction ◽  
Curve Selection

Geometric parameters of road alignment are fundamental elements defining permissible speed and vice versa. Unlike permissible speed, determined operating speed in upgrade projects has a significant impact on the safe movement of transport on the roads. The article reviews the composition of the regional road network in Lithuania, the design speed, the permitted speed, the practical problems of applying the geometry parameters of the road alignment according to the legal documents valid in Lithuania, methods of horizontal curve selection in Lithuania and other countries are analysed in more detail. Comparative initial calculations of horizontal curves were performed using different side friction coefficients. Review summary of analysis conducted and statements are prepared for discussion.

scholarly journals Determination of Applicable Adjacent Horizontal Curve Radii Using Operating Speed

2019 ◽  
Vol 31 (4) ◽  
pp. 443-452
Author(s):  
Dražen Cvitanić ◽  
Biljana Maljković
Keyword(s):  
Dynamic Consistency ◽  
Operating Speed ◽  
Demand Side ◽  
Horizontal Curve ◽  
Driving Dynamic ◽  
The Road ◽  
Design Speed ◽  
Side Friction ◽  
Limiting Values

Design of curves and their adjacent elements presents the greatest safety problem on rural two-lane roads. The use of the existing alignment consistency safety criteria (design, operating speed, and driving dynamic consistency) could have some shortcomings, especially in countries where the project or design speed is in use instead of (higher) operating speed. The consequence is that the designer should use smaller cross fall on curves than needed, while the calculated side friction is lower than in reality. Further, the existing graphs of adjacent curve radii do not take into account that there is a maximum operating speed achieved for a certain radius or long tangent above which it does not increase. This paper presents a methodology for determination of adjacent horizontal curve radii, with and without tangent between, based on the operating speed models which include dependence of operating speeds on tangents and curves on speed of adjacent alignment elements as well as maximum tangent and curve speed. The developed graphs of adjacent radii at the same time include the limiting values of driving dynamic consistency criteria, so the road designer does not need to calculate permissible and demand side friction for every combination of adjacent alignment elements.

Operating speed models for two-lane rural roads in Pakistan

2008 ◽  
Vol 35 (5) ◽  
pp. 443-453 ◽  
Author(s):  
Rizwan A. Memon ◽  
G. B. Khaskheli ◽  
A. Sami Qureshi
Keyword(s):  
Global Positioning System ◽  
Prediction Models ◽  
Geometric Design ◽  
Operating Speed ◽  
Rural Roads ◽  
Horizontal Curves ◽  
Measuring Devices ◽  
Global Positioning ◽  
Speed Prediction ◽  
Design Consistency

One of the suitable techniques used to improve safety on roads is to check the consistency of geometric design. The concept of design consistency has emerged worldwide, but no research has been found to date on design consistency in Pakistan. The most common parameter for the evaluation of design consistency is operating speed. Several models have been developed to predict operating speed on two-lane rural roads. However, these models were based on spot speed data collected through traditional speed measuring devices. This study uses continuous speed profile data collected using a vehicle equipped with a VBox (a global positioning system based device). Eleven test sections were selected in two provinces of Pakistan (i.e., Sindh and Balochistan). Driver behavior is also studied in the present research. Models were developed for prediction of operating speed on horizontal curves and on tangents. Validation of the developed models shows compatibility with the experimental data; hence, the developed speed prediction models can be used to evaluate the geometric design consistency of two-lane rural roads in Pakistan.

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

Formulation and Validation of Operating Speed-Based Design Consistency Models by Bootstrapping

1997 ◽  
Vol 1579 (1) ◽  
pp. 97-103 ◽  
Author(s):  
John McFadden ◽  
Lily Elefteriadou
Keyword(s):  
Additional Data ◽  
Original Data ◽  
Statistical Technique ◽  
Geometric Design ◽  
Operating Speed ◽  
Horizontal Alignment ◽  
Alternative Means ◽  
Design Speed ◽  
Design Consistency ◽  
Consistency Models

Current U.S. policy for designing rural two-lane highways is based on design speed to ensure consistency among consecutive highway segments. The design speed concept, however, does not ensure that a consistent alignment will be achieved. A recent FHWA-sponsored project (Horizontal Alignment Design Consistency for Rural Two-Lane Highways) led to three operating speed-based geometric design consistency models, which have not yet been validated. Traditionally, the validation of such models involves the collection of additional data. The statistical technique known as “bootstrapping” was used to formulate and validate the operating speed-based geometric design consistency models by using the existing FHWA database. Bootstrapping involves random sampling with replacement from the existing database, which becomes the population. One-half of the original data collected are used in formulating the models. The remaining half of the data are subsequently used for validation. The models resulting from bootstrapping were statistically equivalent to the models developed in the FHWA study. In addition, the model validation indicated that the bootstrapping technique used to validate the operating speed models is a viable alternative means of validation. It was concluded that bootstrapping is a very useful tool that can be exploited in many related areas in the transportation field, especially because of the large amounts of data typically required in developing and validating empirical models.

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