Driver tolerance of lateral accelerations on horizontal curves

There are many roadways where existing horizontal curves fail to meet minimum geometric design standards for financial or geographic reasons. Advisory speeds, typically set with a ball-bank indicator, are posted on these curves to ensure that drivers are not subjected to uncomfortable levels of lateral accelerations as they negotiate the curve. The threshold levels of lateral acceleration as estimated by ball-bank indicators vary considerably between jurisdictions with many still basing their guidelines on studies dating back to the 1930s and 1940s. This study investigated present day ball-bank indicator tolerance levels by analyzing actual driver behaviour on 30 curves posted with advisory speeds in New Brunswick. A unique method of data collection involving digital video analysis enabled the development of vehicle speed profiles approaching and throughout the curves. The results indicated that drivers tolerate higher levels of discomfort as they navigate curves than currently assumed. This finding justifies raising the ball-bank indicator threshold levels used for posting advisory speeds. Inconsistencies between actual posted advisory speeds, policy guidelines, and jurisdictional implementation have also been identified. Recommendations address both short and long-term goals of updating ball-bank indicator thresholds used for signing to levels that better represent driver behaviour. Longer-term recommendations address the development of uniform signing standards across Canada so that driver expectation will not be violated between jurisdictions.

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Automobiles on Horizontal Curves: Experiments and Observations

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1628-07 ◽

1998 ◽

Vol 1628 (1) ◽

pp. 50-56 ◽

Cited By ~ 14

Author(s):

Emmanuel Felipe ◽

Francis Navin

Keyword(s):

Latin Square ◽

Lateral Position ◽

Comfort Level ◽

Lateral Acceleration ◽

Small Radius ◽

Vehicle Speed ◽

Large Radius ◽

Horizontal Curves ◽

Upper Limits ◽

Curve Radius

Statistical information on the basic variables involved in driving through a horizontal curve was obtained using a 4×4 Latin square design experiment to measure the action of automobile drivers in test track horizontal curves. The independent variables used in the test curves were speed (comfortable, fast); pavement surface (dry, wet); driver (male, female); and curve radius (16 m, 26 m, 60 m, 100 m). The measured output was the driver’s selected speed and corresponding lateral acceleration. In addition, the passengers indicated their comfort level on a four-point semantic scale. Expert drivers also drove the test curves to establish the upper limits of the driver-vehicle-tire system. Field observations of four curves along a two-lane rural mountain highway measured driver vehicle speed, lateral acceleration, and lateral position. The results indicate that, for a comfortable ride, drivers are limited by their comfortable lateral acceleration on small radius curves and seek the “environmental speed” on large radius curves.

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Passengers’ comfort in horizontal curves on mountain roads: a field study using lateral accelerations

Revista Facultad de Ingeniería Universidad de Antioquia ◽

10.17533/udea.redin.20200578 ◽

2020 ◽

Author(s):

Yasmany D. García-Ramírez ◽

Diego Aguilar-Cárdenas

Keyword(s):

Latin American ◽

Stress Level ◽

Structural Equation ◽

Lateral Acceleration ◽

Equation Modeling ◽

Vehicle Speed ◽

Physical Pain ◽

Horizontal Curves ◽

The Relationship ◽

Real Vehicle

The comfort of passengers is one of the most significant advances in modern passenger transport. Despite its subjectivity, it could be related to the lateral accelerations on horizontal curves. This study aimed to analyze the relationship between passengers' comfort and lateral acceleration in two-lane rural mountain roads. Real-vehicle experiments were performed with 58 passengers on one road in the Ecuadorian Andes. They explored the influence of age, sex, level of stress, level of physical pain, speed, and lateral acceleration on passenger comfort. Two instruments were employed to collect data: a survey conducted to the passengers and a precise GPS device. In the survey, the passengers selected their comfort or discomfort within the curve. The GPS collected the vehicle speed, lateral accelerations and, its trajectory. As a result, it calibrated two models using Structural Equation Modeling (SEM) with the factors: comfort values, stress level and lateral acceleration. Besides, it calibrated six models using linear regression with several thresholds of speed. Differences were found between right and left curves, which had not been detected by previous researchers. The research suggests thresholds of lateral acceleration in mountain roads in a Latin American country that would improve their design for better performance and safety.

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Comfort thresholds for horizontal curve design

Canadian Journal of Civil Engineering ◽

10.1139/l09-075 ◽

2009 ◽

Vol 36 (9) ◽

pp. 1391-1402 ◽

Cited By ~ 4

Author(s):

Dalia Said ◽

Yasser Hassan ◽

A.O. Abd El Halim

Keyword(s):

Research Work ◽

Lateral Acceleration ◽

Horizontal Curve ◽

Driver Behaviour ◽

Rural Roads ◽

Speed Reduction ◽

Horizontal Curves ◽

Friction Factors ◽

Side Friction Factor ◽

Side Friction

A key to better geometric design of highways is designing horizontal curves conforming to driver behaviour. The values of side friction factors in the point mass formula, used for the design of the minimum radius of a horizontal curve, are based on the upper threshold of driver comfort. In the current guidelines, these driver comfort levels were established in research work carried out back in the 1930s. Recently, it was found that faster drivers tend to accept higher comfort thresholds to maintain their speed and minimize speed reduction between curve and tangent. An experiment was designed at Carleton University to collect newer data on driver behaviour including speed and lateral acceleration. The results confirmed the need to revise the values of side friction demand especially for sharp curves. In addition, a model was developed to determine the side friction factor to be used in design or in consistency evaluation of horizontal curves on rural roads and ramps.

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Experience with Short and Long Term Courses of Local Adrenal Steroid Therapy For Ulcerative Colitis

Gastroenterology ◽

10.1016/s0016-5085(62)80117-6 ◽

1962 ◽

Vol 42 (6) ◽

pp. 669-677 ◽

Cited By ~ 18

Author(s):

Jean A. Spencer ◽

Joseph B. Kirsner

Keyword(s):

Ulcerative Colitis ◽

Steroid Therapy ◽

Adrenal Steroid ◽

Short And Long Term

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Short- and Long-Term Results of Total vs Subtotal Thyroid- ectomies in the Surgical Treatment of Graves' Disease

Swiss Surgery ◽

10.1024/1023-9332.7.1.20 ◽

2001 ◽

Vol 7 (1) ◽

pp. 20-24 ◽

Cited By ~ 14

Author(s):

Robert ◽

Mariéthoz ◽

Pache ◽

Bertin ◽

Caulfield ◽

...

Keyword(s):

Recurrent Laryngeal Nerve ◽

Nerve Palsy ◽

Recurrent Laryngeal Nerve Palsy ◽

Laryngeal Nerve ◽

Long Term Results ◽

Graves Disease ◽

Laryngeal Nerve Palsy ◽

Short And Long Term

Objective: Approximately one out of five patients with Graves' disease (GD) undergoes a thyroidectomy after a mean period of 18 months of medical treatment. This retrospective and non-randomized study from a teaching hospital compares short- and long-term results of total (TT) and subtotal thyroidectomies (ST) for this disease. Methods: From 1987 to 1997, 94 patients were operated for GD. Thirty-three patients underwent a TT (mostly since 1993) and 61 a ST (keeping 4 to 8 grams of thyroid tissue - mean 6 g). All patients had received propylthiouracil and/or neo-mercazole and were in a euthyroid state at the time of surgery; they also took potassium iodide (lugol) for ten days before surgery. Results: There were no deaths. Transient hypocalcemia (< 3 months) occurred in 32 patients (15 TT and 17 ST) and persistent hypocalcemia in 8 having had TT. Two patients developed transient recurrent laryngeal nerve palsy after ST (< 3 months). After a median follow-up period of seven years (1-15) with five patients lost to follow-up, 41 patients having had a ST are in a hypothyroid state (73%), thirteen are euthyroid (23%), and two suffered recurrent hyperthyroidism, requiring completion of thyroidectomy. All 33 patients having had TT - with follow-ups averaging two years (0.5-8) - are receiving thyroxin substitution. Conclusions: There were no instances of persistent recurrent laryngeal nerve palsy in either group, but persistent hypoparathyroidism occurred more frequently after TT. Long after ST, hypothyroidism developed in nearly three of four cases, whereas euthyroidy was maintained in only one-fourth; recurrent hyperthyroidy was rare.

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