A model for estimating advisory speeds for horizontal curves in two-lane rural roads

2013 ◽  
Vol 40 (12) ◽  
pp. 1234-1243 ◽  
Author(s):  
Tomás Echaveguren ◽  
Sergio Vargas-Tejeda
Keyword(s):  
Field Data ◽  
Lateral Acceleration ◽  
Operating Speed ◽  
Bank Angle ◽  
Rural Roads ◽  
Horizontal Curves ◽  
Driving Speed ◽  
The Difference ◽  
Advisory Speed ◽  
Design Speed

Horizontal curves are designed using a design speed, which is the speed used to determine the geometric features of highways. In sharp curves, drivers sometimes exceed the design speed. Depending of the difference between design speed and operating speed, drivers can face risky situations, which can be mitigated using signs informing drivers of advisory speeds. Advisory speeds at the horizontal curves are normally estimated as a function of the lateral acceleration for a maximum driving speed, at which comfort is low. This paper proposes an analytical model to estimate advisory speeds based on ball-bank readings and consistency concepts. Field data were obtained using a digital ball-bank indicator, an accelerometer, and a GPS logger. Readings were obtained on 24 test sections at speeds between 40 and 110 km/h. The model proposed yields an advisory speed value and a limit ball-bank angle that require consistent behavior of drivers.

scholarly journals Evaluation of Horizontal Curve Radius Effect on Driving Speed in Two Lane Rural Road. Pilot Study

2020 ◽  
Vol 15 (4) ◽  
pp. 252-270
Author(s):  
Mindaugas Šeporaitis ◽  
Viktoras Vorobjovas ◽  
Audrius Vaitkus
Keyword(s):  
Pilot Study ◽  
Prediction Models ◽  
Speed Limit ◽  
Operating Speed ◽  
Horizontal Curve ◽  
Design Standards ◽  
Horizontal Curves ◽  
Road Design ◽  
Driving Speed ◽  
Design Speed

This paper presents a case study of driving speed at horizontal curves in the regional road. The literature review of operating speed at horizontal curves in regional roads expresses the difference between design speed and driving speed. Driving speed was measured in ten horizontal curves on regional road No. 2610. Collected data was compared to the design speed, various design standards, and Operating Speed Prediction Models for traffic in low-volume roads. Based on result analysis, was proposed initial adjusted minimum radius of the horizontal curve based on operating speed. It is justified that proposed corrections based on operating speed ensure a credible speed limit effect on road safety. The performed experiment showed different tendencies comparing measured driving speed with permitted and design speeds. It was determined that dependent on specific curved section drivers tend to exceed posted speed limit from 17% to 98% of cases, and from 41% to 100% − the design speed in the horizontal curve. This research led to identifying the limitations of experimental research methodology. These limitations are related to experimental Site selection with different combinations of alignment elements, traffic, and accident data. A pilot study showed significant results and gave essential insights into the full-scale research plan. The results are expected to benefit both other researchers and the organisations responsible for the development and implementation of normative technical documents for road design.

scholarly journals Comparison of consistency assessment models for isolated horizontal curves in two-lane rural highways

DYNA ◽  
2015 ◽  
Vol 82 (194) ◽  
pp. 57-65
Author(s):  
Danilo Cárdenas-Aguilar ◽  
Tomás Echaveguren
Keyword(s):  
Spatial Variation ◽  
Operating Speed ◽  
Speed Profile ◽  
Horizontal Curve ◽  
Spatial Variance ◽  
Middle Point ◽  
Rural Roads ◽  
Rural Highways ◽  
Horizontal Curves ◽  
The Difference

This consistency assessment of highways’ geometrical design has the objective of providing safer roads. There are two types of models for consistency assessment: aggregated and disaggregated. The first one considers the difference between design and operating speed at the middle point of isolated horizontal curves. The second one considers the spatial variation of the operating speed profile along the horizontal curve. This paper compares the two types of consistency assessment models, using naturalistic speed and geometry data obtained in 34 horizontal curves of two-lane rural roads in Chile, using a 10 Hz GPS. Results obtained showed that in only 19 cases both methods are equivalent. This equivalence occurred only when operating speed profiles have the lowest spatial variance along the curves. If the operating speed profile has a high variance the consistency level obtained using both methods is different and the better option is combine it.

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.

Speeds of Cars on Horizontal Curves

1998 ◽  
Vol 1612 (1) ◽  
pp. 42-47 ◽  
Author(s):  
Vojo Andjus ◽  
Mihailo Maletin
Keyword(s):  
Free Flow ◽  
Flow Conditions ◽  
Passenger Cars ◽  
Design Standards ◽  
Rural Roads ◽  
Horizontal Curves ◽  
Road Design ◽  
Realistic Approach ◽  
Actual Design ◽  
Design Speed

Revision of existing Yugoslav road-design standards, specifically in the area of road-design speed definition, required studying driver behavior in free-flow conditions in order to define drivers’ responses to the radii of horizontal curves. A specific approach with variable design speed for horizontal curves is discussed and is supported by speed measurements on roads. The pilot research was undertaken on several test sites on Yugoslav two-lane rural roads to collect reliable speed data related to characteristics of horizontal curves. Characteristics of test sites, experimental procedures, data collected, and results of data analyses are described. It is concluded that speeds of free-flow passenger cars show good correlation with radii and that actual design policy with a constant design speed underestimates speeds in radii less than 250 m. Thus, the variable design speed concept is a more realistic approach. Further research on more test sites is recommended.

Operating Speed on Crest Vertical Curves with Limited Stopping Sight Distance

2000 ◽  
Vol 1701 (1) ◽  
pp. 25-31 ◽  
Author(s):  
Daniel B. Fambro ◽  
Kay Fitzpatrick ◽  
Charles W. Russell
Keyword(s):  
Operating Speed ◽  
Design Elements ◽  
Geometric Data ◽  
A Value ◽  
Sight Distance ◽  
The Mean ◽  
The Difference ◽  
Design Speed ◽  
Stopping Sight Distance ◽  
The Relationship

Horizontal and vertical elements of a highway are designed based on an assumed design speed. This concept was developed in the 1930s as a mechanism for designing rural alignments to permit most drivers to operate uniformly at their desired speed. In 1938, AASHO recognized that drivers select a speed influenced by the roadway environment instead of an assumed design speed. Recent research suggests that design speed is no longer the speed adopted by the faster group of drivers but that it has become a value used to establish the sharpness of horizontal and vertical design elements. The objective of this study was to establish the relationship between design and operating speeds for crest vertical curves with limited sight distance. Geometric data and 3,500 paired speeds (speeds at control and crest sections) were collected at 36 sites in 3 states. The results indicated that both the 85th percentile and the mean operating speeds were well above the inferred design speeds of the crest vertical curves for the range of conditions studied and that the lower the design speed the larger the difference between the 85th percentile speed and the design speed. The mean reductions in speed between the control and crest sections tend to increase as available sight distance is decreased; however, the reduction in speed is less than that suggested by current AASHTO criteria.

The Effects of Edgeline Presence on Performance in a Driving Simulator under Sober and Alcohol-Dosed Conditions

1983 ◽  
Vol 27 (4) ◽  
pp. 329-329
Author(s):  
Thomas A. Ranney ◽  
Valerie J. Gawron
Keyword(s):  
Visual Information ◽  
Driving Simulator ◽  
Lateral Acceleration ◽  
Task Demand ◽  
Rural Roads ◽  
Pavement Markings ◽  
Horizontal Curves ◽  
Varying Length ◽  
Alcohol Effects ◽  
And Performance

Accident studies have identified nighttime conditions on rural roads as particular problems for alcohol-impaired drivers. Uneventful driving is hypothesized to result in progressive degradation of tracking performance and a reduced capability to handle the demands of hazardous locations, such as curves. To address these problems, simulations of continuous roadway treatments (i.e., wide edge lines) and spot treatments for curves (i.e., post delineators, chevron alignment signs, patterned pavement markings, and flashing displays) were evaluated experimentally. Twelve subjects drove a simulator under two conditions of task demand and three levels of BAC (0.0, 0.07, 0.12%). The objectives of the study were to determine the effects of alcohol and task demand on driving performance and to determine if providing enhanced visual information concerning roadway alignment would improve the performance of subjects when sober and/or alcohol-dosed. Alcohol effects were measured in terms of overall scenario performance, which included the number of accidents and speed exceedances, and performance on the approach and negotiation of horizontal curves of varying length and curvature. Curve approach and negotiation behavior were also used to evaluate the effects of the roadway treatments. Specific measures included spot measures of speed and lateral placement taken at eight 100-foot intervals along the curve approach and lateral acceleration and position taken continuously over the fixed portion of the curves. The results presented pertain to the effects of the presence of standard and wide edgelines. The discussion relates current findings to those from a previously conducted study.

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.

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.

Assessment of horizontal curves of an existing road using reliability concepts

2005 ◽  
Vol 32 (6) ◽  
pp. 1030-1038 ◽  
Author(s):  
Tomás Echaveguren ◽  
Marcelo Bustos ◽  
Hernán de Solminihac
Keyword(s):  
High Impact ◽  
Point Of View ◽  
Maximum Speed ◽  
Operating Speed ◽  
Skid Resistance ◽  
Operational Conditions ◽  
Horizontal Curves ◽  
Margin Of Safety ◽  
Design Speed ◽  
Curve Radius

Horizontal curves on road are commonly analyzed under design speed point of view, where it is assumed that the maximum speed of a vehicle in a curve is the design speed. The empirical evidence has demonstrated that when the design speed is low, the operating speed tends to be higher. This happens because of an available remaining lateral (or transverse) friction for speeds over design speed. This condition is determined by a speed limit, obtained from the demand and supply equilibrium of friction of a pavement. The difference between operating and design speeds is usually considered as the margin of safety of a horizontal curve on a road. In this study, a methodology to determine the margin of safety of an existing curve is proposed. The methodology is based on the reliability theory by which reliability of operational conditions can be analyzed by using a reliability index as a margin of safety. A case study for light vehicles is evaluated to determine high impact variables over reliability, such as, macrotexture, skid resistance, curve radius, and superelevation. The results obtained in this study demonstrated that curve radius, skid resistance, and macrotexture are variables with high impact over failure probability. In constrast, superelevation has little effect on the failure probability.Key words: reliability, horizontal curves, operating speed, skid resistance, pavement texture.

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