Operational Evaluation of Two-Lane Roundabouts at Freeway Ramp Terminals: Comparison Between Roundabout and Signalized Interchanges

2017 ◽  
Vol 2637 (1) ◽  
pp. 99-113 ◽  
Author(s):  
Zhixia Li ◽  
Madhav V. Chitturi ◽  
Andrea R. Bill ◽  
David A. Noyce
Keyword(s):  
The United States ◽  
Heavy Vehicle ◽  
Simulation Platform ◽  
Heavy Vehicles ◽  
Microscopic Simulation ◽  
Passenger Cars ◽  
Traffic Demand ◽  
Control Delay ◽  
Diamond Interchanges

In the United States, roundabouts have recently been constructed to replace signalized intersections at freeway ramp terminals as both a safety and an operational treatment. In practice, this treatment is in need of guidelines specifying conditions when the roundabout or signalized intersection is more appropriate to assist practitioners in deciding which alternative to choose. In particular, research providing a comprehensive operational comparison between roundabouts and signalized interchanges is lacking. The current research—though a strictly calibrated microscopic simulation platform—analyzes and models the control delay at double-lane roundabouts and signalized interchanges. Both roundabouts and signalized interchanges were modeled in a Vissim simulation platform. Capacity at each roundabout entrance was calibrated and validated separately for passenger cars and heavy vehicles, since both vehicle types have different critical and follow-up headways. The design of the simulation experiments covered 2,880 different scenarios for roundabouts and signalized interchanges with varying ramp and arterial volumes, ramp spacing, and heavy-vehicle percentages. From the simulation results, control delay and level of service of the off-ramp and arterial approaches of roundabouts and signalized diamond interchanges were modeled and compared. Ultimately, guidelines for the selection between double-lane roundabouts and signalized interchanges were developed and presented in the form of look-up tables. These tables provide an easy-to-use tool for practitioners to determine the appropriate double-lane interchange to install under specific combinations of traffic demand, heavy-vehicle percentage, and ramp spacing conditions.

scholarly journals Comparative Analysis of Effects of Heavy Vehicles on Roads in Southern and Northern Nigeria

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
C. C. Osadebe ◽  
H. A. Quadri
Keyword(s):  
Northern Region ◽  
Design Guidelines ◽  
Traffic Volume ◽  
Southern Region ◽  
Heavy Vehicle ◽  
Heavy Vehicles ◽  
Passenger Cars ◽  
The Road ◽  
Equivalency Factors ◽  
On The Road

The prevalence of flexible pavement deterioration in the country has been adduced largely by highway researchers to trucks or heavy vehicles carrying much in excess of permitted legal limits. This study investigated levels of deterioration of Abuja-Kaduna-Kano road (Northern region) and Port Harcourt-Enugu road (Southern region) caused by heavy vehicles through a 14 day traffic counts conducted at 5 strategic points each in the Northern and Southern regions. Traffic data generated were analyzed with AASHTO Design Guidelines (1993) to evaluate Equivalent Single Axle Loads (ESALs) and Vehicle Damage effects on the road. The Traffic Volume, Average Daily Traffic (ADT), and Heavy Vehicle per day (HV/day) were estimated to be 2,063,977; 147,427; and 12,246 respectively in the Northern region, while in the Southern region they were estimated to be 750,381; 53,670; and 20,951 respectively. Motorcycles, Passenger cars, Mini-buses/Pick-ups, and Heavy vehicles constitute 18.7%, 49.7%, 23.3% and 8.31% of the total traffic volume respectively in the Northern region while in the South they constitute 4.6%, 30.1%, 26.2% and 39.1% respectively. ESALs were estimated according to AASHTO Design Guidelines in the Northern and Southern regions as 547,730 and 836,208 respectively. An average Load Equivalency Factors (LEFs) of 3.43 and 3.02 were estimated for each heavy vehicle plying the Northern and Southern roads respectively and this could explain some failures (alligator cracks, potholes, depressions, linear or longitudinal cracks along the centre line amongst others) inherent on the road.

Analysing the Performance of a Fuzzy Lane Changing Model Using Data Mining

2015 ◽  
pp. 1540-1566
Author(s):  
Sara Moridpour
Keyword(s):  
Traffic Safety ◽  
Traffic Simulation ◽  
Heavy Traffic ◽  
Heavy Vehicle ◽  
Heavy Vehicles ◽  
Passenger Cars ◽  
Lane Changing ◽  
Microscopic Traffic Simulation ◽  
Traffic Characteristics ◽  
Using Data

Heavy vehicles have substantial impact on traffic flow particularly during heavy traffic conditions. Large amount of heavy vehicle lane changing manoeuvres may increase the number of traffic accidents and therefore reduce the freeway safety. Improving road capacity and enhancing traffic safety on freeways has been the motivation to establish heavy vehicle lane restriction strategies to reduce the interaction between heavy vehicles and passenger cars. In previous studies, different heavy vehicle lane restriction strategies have been evaluated using microscopic traffic simulation packages. Microscopic traffic simulation packages generally use a common model to estimate the lane changing of heavy vehicles and passenger cars. The common lane changing models ignore the differences exist in the lane changing behaviour of heavy vehicle and passenger car drivers. An exclusive fuzzy lane changing model for heavy vehicles is developed and presented in this chapter. This fuzzy model can increase the accuracy of simulation models in estimating the macroscopic and microscopic traffic characteristics. The results of this chapter shows that using an exclusive lane changing model for heavy vehicles, results in more reliable evaluation of lane restriction strategies.

Analysing the Performance of a Fuzzy Lane Changing Model Using Data Mining

2013 ◽  
pp. 289-315 ◽  
Author(s):  
Sara Moridpour
Keyword(s):  
Traffic Safety ◽  
Traffic Simulation ◽  
Heavy Traffic ◽  
Heavy Vehicle ◽  
Heavy Vehicles ◽  
Passenger Cars ◽  
Lane Changing ◽  
Microscopic Traffic Simulation ◽  
Traffic Characteristics ◽  
Using Data

Heavy vehicles have substantial impact on traffic flow particularly during heavy traffic conditions. Large amount of heavy vehicle lane changing manoeuvres may increase the number of traffic accidents and therefore reduce the freeway safety. Improving road capacity and enhancing traffic safety on freeways has been the motivation to establish heavy vehicle lane restriction strategies to reduce the interaction between heavy vehicles and passenger cars. In previous studies, different heavy vehicle lane restriction strategies have been evaluated using microscopic traffic simulation packages. Microscopic traffic simulation packages generally use a common model to estimate the lane changing of heavy vehicles and passenger cars. The common lane changing models ignore the differences exist in the lane changing behaviour of heavy vehicle and passenger car drivers. An exclusive fuzzy lane changing model for heavy vehicles is developed and presented in this chapter. This fuzzy model can increase the accuracy of simulation models in estimating the macroscopic and microscopic traffic characteristics. The results of this chapter shows that using an exclusive lane changing model for heavy vehicles, results in more reliable evaluation of lane restriction strategies.

Guidelines for Selecting Single-Point Urban and Diamond Interchanges: Nationwide Survey and Literature Review

1998 ◽  
Vol 1612 (1) ◽  
pp. 48-54
Author(s):  
Michelle J. Smith ◽  
Nicholas J. Garber
Keyword(s):  
Literature Review ◽  
Traffic Congestion ◽  
Single Point ◽  
Nationwide Survey ◽  
The United States ◽  
Sources Of Information ◽  
Traffic Demand ◽  
Geometric Conditions ◽  
New Type ◽  
Diamond Interchanges

Metropolitan areas in the United States are experiencing a steep increase in traffic growth and traffic congestion on their urban freeways. In the past, the most prevalent type of urban interchange has been the diamond interchange (DI). In more recent years, however, to overcome the need for significant additional right-of-way that is generally required for this type of interchange and still respond to increased traffic demand, a new type of interchange has emerged: the single-point urban interchange (SPUI). Traffic engineers do not agree about the relative operational efficiency of the SPUI compared with the DI. Also, the unfamiliar geometry and operation of the SPUI and its large, uncontrolled conflict area have raised several concerns about the safety of motorists who travel through it. The purpose of this study was to evaluate and compare the safety and operational characteristics of the SPUI and DI and to develop guidelines that identify traffic and geometric conditions that favor one over the other. We surveyed state traffic engineers across the nation about their experiences and opinions of the two interchanges in terms of operational performance and safety. A complete literature review on the subject revealed significant findings as well. We used both of these sources of information to develop guidelines to aid traffic engineers in selecting and designing the appropriate type of interchange.

scholarly journals Aerodynamic integration produces a vehicle shape with a negative drag coefficient

2021 ◽  
Vol 118 (27) ◽  
pp. e2106406118
Author(s):  
Kambiz Salari ◽  
Jason M. Ortega
Keyword(s):  
Aerodynamic Drag ◽  
The United States ◽  
Body Axis ◽  
Heavy Vehicle ◽  
Heavy Vehicles ◽  
Drag Coefficients ◽  
The Road ◽  
On The Road ◽  
Vehicle Shape ◽  
Dynamics Simulations

Negative drag coefficients are normally associated with a vessel outfitted with a sail to extract energy from the wind and propel the vehicle forward. Therefore, the notion of a heavy vehicle, that is, a semi truck, that generates negative aerodynamic drag without a sail or any external appendages may seem implausible, especially given the fact that these vehicles have some of the largest drag coefficients on the road today. However, using both wind tunnel measurements and computational fluid dynamics simulations, we demonstrate aerodynamically integrated vehicle shapes that generate negative body-axis drag in a crosswind as a result of large negative frontal pressures that effectively “pull” the vehicle forward against the wind, much like a sailboat. While negative body-axis drag exists only for wind yaw angles above a certain analytical threshold, the negative frontal pressures exist at smaller yaw angles and subsequently produce body-axis drag coefficients that are significantly less than those of modern heavy vehicles. The application of this aerodynamic phenomenon to the heavy vehicle industry would produce sizable reductions in petroleum use throughout the United States.

A Rear-End Protection Device for Heavy Vehicles

2003 ◽  
Author(s):  
Ali O. Atahan ◽  
Abhishek S. Joshi ◽  
Moustafa El-Gindy
Keyword(s):  
Finite Element ◽  
Safety Concern ◽  
Heavy Vehicle ◽  
Finite Element Models ◽  
Heavy Vehicles ◽  
Passenger Cars ◽  
Passenger Car ◽  
Impact Performance ◽  
Optimum Height ◽  
Support Conditions

Rear underride crashes, particularly with heavy vehicles, constitute a serious safety concern for passenger cars. Several solutions to this emerging concern have been proposed by responsible agencies. Recent rear-end crashes with heavy vehicles show that a properly used rear underride guard devices can slow down impacting vehicle in a controlled manner. Moreover, with the use of these devices, the severity of crashes can be reduced and loss of lives can be prevented. In this paper, a special underride guard device is designed for heavy vehicle use. The height of the device from ground and support conditions are varied to evaluate and compare the crash performances. Finite element models of these particular designs are constructed and models are impacted by a passenger car model traveling at two different speeds of 48 km/h and 64 km/h. LS-DYNA, a non-linear finite element code capable of analyzing large deformations is used for the analysis. Vehicle decelerations, energy dissipations and passenger car crush characteristics are compared to determine the acceptability of each design. Based on the simulation study, an optimum height from ground and support condition are determined for acceptable impact performance for heavy vehicle mounted rear -end underride guard devices against passenger vehicle impacts.

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

2018 ◽  
Vol 2672 (17) ◽  
pp. 72-82 ◽  
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.

scholarly journals Natural History and Evolution of Anti-Interferon-γ Autoantibody-Associated Immunodeficiency Syndrome in Thailand and the United States

2019 ◽  
Vol 71 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Gloria H Hong ◽  
Ana M Ortega-Villa ◽  
Sally Hunsberger ◽  
Ploenchan Chetchotisakd ◽  
Siriluck Anunnatsiri ◽  
...  
Keyword(s):  
United States ◽  
Natural History ◽  
The United States ◽  
Interferon Γ ◽  
Mycobacterium Abscessus ◽  
Annual Data ◽  
Persistent Infections ◽  
Ifn Γ ◽  
Immunodeficiency Syndrome

Abstract Background The natural history of anti-interferon-γ (IFN-γ) autoantibody-associated immunodeficiency syndrome is not well understood. Methods Data of 74 patients with anti-IFN-γ autoantibodies at Srinagarind Hospital, Thailand, were collected annually (median follow-up duration, 7.5 years). Annual data for 19 patients and initial data for 4 patients with anti-IFN-γ autoantibodies at the US National Institutes of Health were collected (median follow-up duration, 4.5 years). Anti-IFN-γ autoantibody levels were measured in plasma samples. Results Ninety-one percent of US patients were of Southeast Asian descent; there was a stronger female predominance (91%) in US than Thai (64%) patients. Mycobacterium abscessus (34%) and Mycobacterium avium complex (83%) were the most common nontuberculous mycobacteria in Thailand and the United States, respectively. Skin infections were more common in Thailand (P = .001), whereas bone (P < .0001), lung (P = .002), and central nervous system (P = .03) infections were more common in the United States. Twenty-four percent of Thai patients died, most from infections. None of the 19 US patients with follow-up data died. Anti-IFN-γ autoantibody levels decreased over time in Thailand (P < .001) and the United States (P = .017), with either cyclophosphamide (P = .01) or rituximab therapy (P = .001). Conclusions Patients with anti-IFN-γ autoantibodies in Thailand and the United States had distinct demographic and clinical features. While titers generally decreased with time, anti-IFN-γ autoantibody disease had a chronic clinical course with persistent infections and death. Close long-term surveillance for new infections is recommended.

scholarly journals How Family Physicians Practice the Principle of Remission Along the Glycemic Continuum

2020 ◽  
Vol 11 ◽  
pp. 215013272097774
Author(s):  
Stephanie T. Fulleborn ◽  
Paul F. Crawford ◽  
Jeremy T. Jackson ◽  
Christy J.W. Ledford
Keyword(s):  
Type 2 Diabetes ◽  
Medical Record ◽  
The United States ◽  
Case Scenario ◽  
Cross Sectional ◽  
Normal Glucose ◽  
Normal Glucose Regulation

Introduction Recent evidence reveals that diabetes and prediabetes (preDM) can be reversed to normal glucose regulation (NGR) through significant weight loss, but how physicians clinically identify the principles of partial and complete remission of diabetes is largely unknown. Methods As part of the cross-sectional omnibus survey conducted in March 2019 at a professional annual meeting in the United States, physician participants answered case scenario questions about the diagnosis and documentation of patients with preDM and type 2 diabetes (T2DM). Results Of the registered conference attendees, 387 (72.7%) responded. When presented with the initial case of preDM, 201 physicians (70.8%) selected R73.03 Prediabetes. In a follow-up encounter with improved lab results, 118 physicians (58.7%) indicated that they would not chart any diabetes-related code and 62 (30.8%) would chart preDM again. When presented with the case of T2DM, 256 physicians (90.1%) indicated E11.0–E11.9 Type 2 Diabetes. In the follow-up encounter, only 38 (14.8%) coded a diagnosis reflecting remission from T2DM to prediabetes and 211 (82.4%) charted T2DM. Conclusion Physicians may be reluctant to document diabetes regression as there is little evidence for long-term outcomes and “downgrading” the diagnosis in the medical record may cause screenings to be missed. Documenting this regression in the medical record should communicate the accurate point on the continuum of glucose intolerance with both the patient and the care team.

scholarly journals Testing telediagnostic thyroid ultrasound in Peru: a new horizon in expanding access to imaging in rural and underserved areas

2021 ◽  
Author(s):  
T. J. Marini ◽  
S. L. Weiss ◽  
A. Gupta ◽  
Y. T. Zhao ◽  
T. M. Baran ◽  
...  
Keyword(s):  
Thyroid Nodule ◽  
Standard Of Care ◽  
The United States ◽  
Epidemiological Studies ◽  
Thyroid Ultrasound ◽  
Target Region ◽  
Experienced Radiologist ◽  
Significant Difference ◽  
Size Evaluation

Abstract Purpose Thyroid ultrasound is a key tool in the evaluation of the thyroid, but billions of people around the world lack access to ultrasound imaging. In this study, we tested an asynchronous telediagnostic ultrasound system operated by individuals without prior ultrasound training which may be used to effectively evaluate the thyroid and improve access to imaging worldwide. Methods The telediagnostic system in this study utilizes volume sweep imaging (VSI), an imaging technique in which the operator scans the target region with simple sweeps of the ultrasound probe based on external body landmarks. Sweeps are recorded and saved as video clips for later interpretation by an expert. Two operators without prior ultrasound experience underwent 8 h of training on the thyroid VSI protocol and the operation of the telemedicine platform. After training, the operators scanned patients at a health center in Lima. Telediagnostic examinations were sent to the United States for remote interpretation. Standard of care thyroid ultrasound was performed by an experienced radiologist at the time of VSI examination to serve as a reference standard. Results Novice operators scanned 121 subjects with the thyroid VSI protocol. Of these exams, 88% were rated of excellent image quality showing complete or near complete thyroid visualization. There was 98.3% agreement on thyroid nodule presence between VSI teleultrasound and standard of care ultrasound (Cohen’s kappa 0.91, P < 0.0001). VSI measured the thyroid size, on average, within 5 mm compared to standard of care. Readers of VSI were also able to effectively characterize thyroid nodules, and there was no significant difference in measurement of thyroid nodule size (P = 0.74) between VSI and standard of care. Conclusion Thyroid VSI telediagnostic ultrasound demonstrated both excellent visualization of the thyroid gland and agreement with standard of care thyroid ultrasound for nodules and thyroid size evaluation. This system could be deployed for evaluation of palpable thyroid abnormalities, nodule follow-up, and epidemiological studies to promote global health and improve the availability of diagnostic imaging in underserved communities.

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