Speeds of Cars on Horizontal Curves

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.

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Safety at Curves and Road Geometry Standards in Some European Countries

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198196152300112 ◽

1996 ◽

Vol 1523 (1) ◽

pp. 99-106 ◽

Cited By ~ 4

Author(s):

Thierry Brenac

Keyword(s):

Urban Areas ◽

National Standards ◽

European Countries ◽

Design Standards ◽

The Road ◽

Horizontal Curves ◽

Road Design ◽

Road Geometry ◽

Design Speed ◽

Curve Geometry

This paper deals with safety at horizontal curves on two-lane roads outside urban areas and the way the road design standards of different European countries account for this safety aspect. After a review of some research results, the main aspects of curve geometry and the curve's place in the horizontal alignment are analyzed. The main conclusions are that the traditional design speed approach is insufficient and that formal complementary rules in road design standards, especially to improve compatibility between successive elements of the alignment, must be introduced. If such complementary rules already exist in some national standards, they are neither frequent nor homogeneous throughout the different countries, and it seems that they are not based on sufficiently developed knowledge.

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

The Baltic Journal of Road and Bridge Engineering ◽

10.7250/bjrbe.2020-15.503 ◽

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.

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Design radius requirements for simple horizontal curves on three-dimensional alignments

Canadian Journal of Civil Engineering ◽

10.1139/l03-022 ◽

2003 ◽

Vol 30 (6) ◽

pp. 1022-1033 ◽

Cited By ~ 11

Author(s):

Said M Easa ◽

Essam Dabbour

Keyword(s):

Three Dimensional ◽

Design Guidelines ◽

Comfort Level ◽

Vertical Alignment ◽

Passenger Cars ◽

Minimum Radius ◽

Horizontal Curves ◽

Design Speed ◽

Side Friction ◽

Mathematical Relationships

Current North American design guides have established mathematical relationships to calculate the minimum radius required for horizontal curves as a function of design speed, maximum superelevation, and maximum side friction. For three-dimensional (3-D) alignments, the design guides consider the alignment as two separate horizontal and vertical alignments and consequently ignore the effect of vertical alignment. This paper evaluates the effect of vertical alignment on minimum radius requirements using computer simulation, with a focus on trucks. For 3-D alignments, the results showed that existing design guidelines for minimum radius need to be increased by as much as 20% to achieve the same comfort limit on flat horizontal curves. It is interesting to note that in some cases truck rollover occurred before the side-friction comfort level is reached. This indicates the need for developing a different design control for trucks on 3-D alignments than the comfort criterion used for passenger cars on flat horizontal curves. Based on the simulation results, mathematical models for design radius requirements for passenger cars and trucks were developed.Key words: geometric design, horizontal curve radius, three-dimensional alignments, vehicle stability.

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

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2012-0549 ◽

2013 ◽

Vol 40 (12) ◽

pp. 1234-1243 ◽

Cited By ~ 2

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.

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Speed Prediction Models for Trucks on Horizontal Curves of Two-Lane Rural Roads

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198118776111 ◽

2018 ◽

Vol 2672 (17) ◽

pp. 72-82 ◽

Cited By ~ 3

Author(s):

David Llopis-Castelló ◽

Brayan González-Hernández ◽

Ana María Pérez-Zuriaga ◽

Alfredo García

Keyword(s):

Road Safety ◽

Prediction Models ◽

Gps Tracking ◽

Heavy Vehicle ◽

Heavy Vehicles ◽

Passenger Cars ◽

Rural Roads ◽

Horizontal Curves ◽

Speed Prediction ◽

Design Consistency

Road safety is closely related to geometric design consistency, which is usually assessed by examining operating speed. Most consistency models only consider passenger car speeds, even though the interaction between passenger cars and heavy vehicles plays a pivotal role in road safety. This is due to the fact that there are too few models to estimate heavy vehicle speeds. This study aims to develop speed prediction models for heavy vehicles on horizontal curves of two-lane rural roads. To do this, continuous speed profiles were collected by using Global Positioning System (GPS) tracking devices on 11 road sections. Truck speeds were analyzed on 105 horizontal curves. The results showed that the radius of the horizontal curve and the grade at the point of curvature have a significant influence on heavy vehicle speeds. In this regard, vertical alignment only has a significant effect on truck speeds along upgrades. In addition, different trends were identified for loaded and unloaded trucks, so different speed models were calibrated for each of them. As a result, heavy vehicle speeds were adversely affected by grades greater than 3%. This phenomenon was larger for loaded trucks than for unloaded ones. Finally, the calibrated 85th and 15th percentile speed models were compared with those developed previously. As a conclusion, the use of the proposed models in this study was recommended on Spanish two-lane rural roads due mainly to the different characteristics of heavy vehicles around the world.

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Sustainable design of rural roads with 2+1 road design: Levels of service and traffic flow performance

KSCE Journal of Civil Engineering ◽

10.1007/s12205-016-1696-1 ◽

2016 ◽

Vol 20 (3) ◽

pp. 1032-1039 ◽

Cited By ~ 1

Author(s):

Jaisung Choi ◽

Youngrok Kim ◽

Torsten Bergh ◽

Sangyoup Kim ◽

Sungkyu Kim

Keyword(s):

Traffic Flow ◽

Sustainable Design ◽

Rural Roads ◽

Road Design ◽

Levels Of Service

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Speed Models for Motorcycle Riders for Two-lane Rural Roads

WSEAS TRANSACTIONS ON ENVIRONMENT AND DEVELOPMENT ◽

10.37394/232015.2021.17.57 ◽

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.

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