Impact of Geometry and Operations on Left-Turn Gap Acceptance at Signalized Intersections with Permissive Indication

2021 ◽  
pp. 036119812110114
Author(s):  
Boris Claros ◽  
Madhav Chitturi ◽  
Andrea Bill ◽  
David A. Noyce
Keyword(s):  
The United States ◽  
Signalized Intersections ◽  
Video Data ◽  
Likelihood Method ◽  
Speed Limit ◽  
Gap Acceptance ◽  
Site Specific ◽  
The Mean ◽  
Saturation Flow

Critical and follow-up headways are the foundation for estimating the saturation flow of permissive left-turns at signalized intersections. Current critical and follow-up headways recommended in the 2016 Highway Capacity Manual (HCM) are based on limited data collected from five intersections in Texas in the 1970s. This study analyzed over 2,500 left-turning vehicles at 45 intersection approaches, provides insights into gap acceptance parameters, and evaluates the effect of different site-specific factors. Video data were collected and processed from different geographical regions in the United States—Arizona, Florida, North Carolina, Virginia, and Wisconsin. Using the maximum likelihood method to estimate gap acceptance parameters, the mean critical headway was 4.87 s and the mean follow-up headway was 2.73 s. To account for site-specific characteristics, the effect of several geometric and operational variables on critical and follow-up headway were explored. Through a meta-regression analysis, the posted speed limit and width of opposing travel lanes were found to have a significant effect on gap acceptance parameters. Results showed that with decreasing posted speed limit and width of opposing lanes, critical and follow-up headways also decreased, resulting in greater saturation flows. When site-specific saturation flow estimates were compared with HCM saturation flow estimates, the differences ranged from −30% to +23%. This paper quantifies and illustrates the impact of site-specific characteristics on gap acceptance parameters and saturation flow.

Investigation of saturation flow rate using video camera at signalized intersections in Jordan

2020 ◽  
Vol 11 (1) ◽  
pp. 216-226
Author(s):  
Bara’ W. Al-Mistarehi ◽  
Ahmad H. Alomari ◽  
Mohamad S. Al Zoubi
Keyword(s):  
Flow Rate ◽  
Standard Procedure ◽  
Video Camera ◽  
Signalized Intersections ◽  
Speed Limit ◽  
Local Conditions ◽  
Highway Capacity Manual ◽  
Saturation Flow Rate ◽  
Turning Radius ◽  
Saturation Flow

AbstractThis study aimed to investigate a potential list of variables that may have an impact on the saturation flow rate (SFR) associated with different turning movements at signalized intersections in Jordan. Direct visits to locations were conducted, and a video camera was used. Highway capacity manual standard procedure was followed to collect the necessary traffic data. Multiple linear regression was performed to classify the factors that impact the SFR and to find the optimal model to foretell the SFR. Results showed that turning radius, presence of camera enforcement, and the speed limit are the significant factors that influence SFR for shared left- and U-turning movements (LUTM) with R2 = 76.9%. Furthermore, the presence of camera enforcement, number of lanes, speed limit, city, traffic volume, and area type are the factors that impact SFR for through movements only (THMO) with R2 = 69.6%. Also, it was found that the SFR for LUTM is 1611 vehicles per hour per lane (VPHPL),which is less than the SFR for THMO that equals to 1840 VPHPL. Calibration and validation of SFR based on local conditions can improve the efficiency of infrastructure operation and planning activities because vehicles’ characteristics and drivers’ behavior change over time.

Abstract 1122‐000142: Safety and Efficacy of Surpass Streamline for Intracranial Aneurysms: A Multicenter US Real‐World Experience (SESSIA)

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Juan Vivanco‐Suarez ◽  
Alan Mendez‐Ruiz ◽  
Farooqui Mudassir ◽  
Cynthia B Zevallos ◽  
Milagros Galecio‐Castillo ◽  
...  
Keyword(s):  
Real World ◽  
Intracranial Aneurysms ◽  
The United States ◽  
Chromium Alloy ◽  
Cobalt Chromium ◽  
Anterior Circulation ◽  
Safety And Efficacy ◽  
Post Marketing ◽  
The Mean

Introduction : Flow diversion has established itself as standard treatment of wide complex intracranial aneurysms (IA). Its recognition has been validated with positive occlusion rates and favorable clinical outcomes. The Surpass Streamline (SS) flow diverter (FD) is a braided cobalt/chromium alloy implant with 72 or 96 wires approved by the FDA in 2018. The aim of this study is to determine the safety and efficacy of the SS in a post‐marketing large US cohort. Methods : We performed a multicenter, retrospective study for consecutive patients treated with the SS FD for IA between January 2018 and June 2021 in the United States. Inclusion criteria for participants were: 1. Adults (≥ 18 years) and 2. Treatment with SS FD for IA. Primary safety end point was a major ipsilateral stroke (increase in National Institutes of Health Stroke Scale Score of ≥ 4) or neurological death within 12 months. Primary efficacy was assessed using the 3‐point Raymond‐Roy (RR) occlusion scale on digital subtraction angiography (DSA) at 6‐12‐month follow‐up. Results : A total of 276 patients with 313 aneurysms were enrolled. The median age was 59 years and 199 (72%) were females. The most common comorbidities included hypertension in 156 (57%) subjects followed by hyperlipidemia in 76 (28%) patients. One hundred and twenty‐two (44%) patients were asymptomatic while subarachnoid hemorrhage was present in only 10 (4%) patients. A total of 143 (46%) aneurysms were left‐sided. Aneurysms were located as follows: 274 (88%) were in the anterior circulation with paraophthalmic being the most common in 120 (38%) followed by petrocavernous ICA in 81 (26%); 33 (11%) aneurysms were located in the posterior circulation with basilar trunk being the most common in 14 (5%). The mean maximum aneurysm dome width was 5.77 ± 4.7 mm, neck width 4.22 ± 3.8 mm and dome to neck ratio was 1.63 ± 1.3 mm. The mean number of SS FD implanted per aneurysm was 1.06 (range 1–3) with more than one SS FD implanted in 21 (7%) aneurysms. Modified Rankin Scale (mRS) of 0–2 was present in 206/213 (97%) patients at 6–12 month follow‐up. The complete aneurysm occlusion (RR 1) rate was 145/175 (83%) among subjects who had angiographic follow‐up at 6–12 months. Major stroke and death was encountered in 7 (2%) and 5 (1.8%) of the patients respectively. Conclusions : Our data represent the largest real‐world study using SS FD. These results corroborate its post‐marketing safety and efficacy for the treatment of intracranial aneurysms showing more favorable rates to the initial experience during SCENT trial.

Pedestrian Behavior at Signalized Intersection Crosswalks: Observational Study of Factors Associated with Distracted Walking, Pedestrian Violations, and Walking Speed

2018 ◽  
Vol 2672 (35) ◽  
pp. 1-12 ◽  
Author(s):  
Brendan J. Russo ◽  
Emmanuel James ◽  
Cristopher Y. Aguilar ◽  
Edward J. Smaglik
Keyword(s):  
Traffic Safety ◽  
Walking Speed ◽  
The United States ◽  
Ordinary Least Squares ◽  
Signalized Intersections ◽  
Video Data ◽  
High Definition ◽  
Pedestrian Behavior ◽  
Factors Associated ◽  
Walking Speeds

In the past two decades, cell phone and smartphone use in the United States has increased substantially. Although mobile phones provide a convenient way for people to communicate, the distraction caused by the use of these devices has led to unintended traffic safety and operational consequences. Although it is well recognized that distracted driving is extremely dangerous for all road users (including pedestrians), the potential impacts of distracted walking have not been as comprehensively studied. Although practitioners should design facilities with the safety, efficiency, and comfort of pedestrians in mind, it is still important to investigate certain pedestrian behaviors at existing facilities to minimize the risk of pedestrian–vehicle crashes, and to reduce behaviors that may unnecessarily increase delay at signalized intersections. To gain new insights into factors associated with distracted walking, pedestrian violations, and walking speed, 3,038 pedestrians were observed across four signalized intersections in New York and Arizona using high-definition video cameras. The video data were reduced and summarized, and an ordinary least squares (OLS) regression model was estimated to analyze factors affecting walking speeds. In addition, binary logit models were estimated to analyze both pedestrian distraction and pedestrian violations. Ultimately, several site- and pedestrian-specific variables were found to be significantly associated with pedestrian distraction, violation behavior, and walking speeds. The results provide important information for researchers, practitioners, and legislators, and may be useful in planning strategies to reduce or mitigate the impacts of pedestrian behavior that may be considered unsafe or potentially inefficient.

scholarly journals Management and Treatment of Concussions via Tele-Concussion in a Pediatric Setting: Methodological Approach and Descriptive Analysis

10.2196/19924 ◽  
2020 ◽  
Vol 3 (2) ◽  
pp. e19924
Author(s):  
Todd Caze II ◽  
Gregory P Knell ◽  
John Abt ◽  
Scott O Burkhart
Keyword(s):  
United States ◽  
Clinical Care ◽  
The United States ◽  
Return To Play ◽  
Care Process ◽  
Descriptive Data ◽  
Pediatric Concussion ◽  
Return To Learn ◽  
The Mean

Background Approximately 2 million children in the United States sustain a concussion annually, resulting in an economic impact as high as US $20 billion. Patients who receive treatment at concussion specialty clinics, versus primary care, experience faster recovery, thereby reducing patient burden and subsequent medical-related costs. Accessibility to specialty clinics is typically limited by the availability of in-office visits. This is particularly relevant in light of the severe acute respiratory syndrome coronavirus 2 pandemic and subsequent guidance to eliminate all non–medically necessary in-clinic visits. Telehealth has been used to effectively deliver in-clinic care across several disciplines including psychiatry, psychology, and neuropsychology. However, a model of telehealth delivered concussion assessment, treatment, and management has not been established. Objective The purposes of this paper are to describe a pediatric concussion specialty clinic’s experiences in delivering telehealth concussion services and to provide preliminary descriptive data on a sample of pediatric telehealth patients with concussions. Methods The specialty pediatric concussion clinic described here began providing telehealth services in 2019 and is part of the largest and fastest-growing telehealth hospital network in the United States. The clinical care process will be described, including accessing the telehealth platform, assessment during the initial appointment, injury management including communication with relevant patient stakeholders (eg, parent or guardians, athletic trainers), dissemination of rehabilitation exercises, and nature of follow-up visits. Descriptive data will include patient demographics, the radius of care, the time between the date of injury and initial visit, the average number of follow-up visits, and days until medically cleared for return-to-learn and return-to-play. Results The analytic sample included 18 patients with concussions who were seen for all of their visits via telehealth between August 2019 and April 2020. The mean age of the sample was 14.5 (SD 2.5) years. The radius of care was a median of 17 (IQR 11.0-31.0) miles from the clinic with a median time between injury and the first visit of 21 (IQR 6.0-41.5) days. The mean number of visits was 2.2 (SD 0.8) with a median days between visits of 5.4 (IQR 3.0-9.3) to manage and treat the concussion. Of the 18 patients, 55.6% (n=10) were medically cleared for return-to-learn or -play in a median of 15.5 (IQR 11.0-29.0) days. Conclusions Limited access to health care is a well-understood barrier for receiving quality care. Subsequently, there are increasing demands for flexibility in delivering concussion services remotely and in-clinic. This is the first paper to provide a clinically relevant framework for the assessment, management, and treatment of acute concussion via telehealth in a pediatric population.

Early implementation of stereoelectroencephalography in children: a multiinstitutional case series

2021 ◽  
pp. 1-8
Author(s):  
Jacob R. Lepard ◽  
Irene Kim ◽  
Anastasia Arynchyna ◽  
Sean M. Lew ◽  
Robert J. Bollo ◽  
...  
Keyword(s):  
Case Series ◽  
The United States ◽  
Postoperative Hemorrhage ◽  
Pediatric Epilepsy ◽  
Continuous Variables ◽  
Early Implementation ◽  
Significant Difference ◽  
Normative Practice ◽  
The Mean

OBJECTIVE Pediatric stereoelectroencephalography (SEEG) has been increasingly performed in the United States, with published literature being limited primarily to large single-center case series. The purpose of this study was to evaluate the experience of pediatric epilepsy centers, where the technique has been adopted in the last several years, via a multicenter case series studying patient demographics, outcomes, and complications. METHODS A retrospective cohort methodology was used based on the STROBE criteria. ANOVA was used to evaluate for significant differences between the means of continuous variables among centers. Dichotomous outcomes were assessed between centers using a univariate and multivariate logistic regression. RESULTS A total of 170 SEEG insertion procedures were included in the study from 6 different level 4 pediatric epilepsy centers. The mean patient age at time of SEEG insertion was 12.3 ± 4.7 years. There was no significant difference between the mean age at the time of SEEG insertion between centers (p = 0.3). The mean number of SEEG trajectories per patient was 11.3 ± 3.6, with significant variation between centers (p < 0.001). Epileptogenic loci were identified in 84.7% of cases (144/170). Patients in 140 cases (140/170, 82.4%) underwent a follow-up surgical intervention, with 47.1% (66/140) being seizure free at a mean follow-up of 30.6 months. An overall postoperative hemorrhage rate of 5.3% (9/170) was noted, with patients in 4 of these cases (4/170, 2.4%) experiencing a symptomatic hemorrhage and patients in 3 of these cases (3/170, 1.8%) requiring operative evacuation of the hemorrhage. There were no mortalities or long-term complications. CONCLUSIONS As the first multicenter case series in pediatric SEEG, this study has aided in establishing normative practice patterns in the application of a novel surgical technique, provided a framework for anticipated outcomes that is generalizable and useful for patient selection, and allowed for discussion of what is an acceptable complication rate relative to the experiences of multiple institutions.

Intermediate-term Experience With the STAR Total Ankle in the United States

2018 ◽  
Vol 40 (3) ◽  
pp. 268-275 ◽  
Author(s):  
Evan M. Loewy ◽  
Thomas H. Sanders ◽  
Arthur K. Walling
Keyword(s):  
United States ◽  
Perioperative Complications ◽  
Case Series ◽  
Major Complication ◽  
The United States ◽  
Complication Rates ◽  
Level Of Evidence ◽  
Patient Reported ◽  
The Mean

Background: Limited intermediate and no real long-term follow-up data have been published for total ankle arthroplasty (TAA) in the United States. This is a report of clinical follow-up data of a prospective, consecutive cohort of patients who underwent TAA by a single surgeon from 1999 to 2013 with the Scandinavian Total Ankle Replacement (STAR) prosthesis. Methods: Patients undergoing TAA at a single US institution were enrolled into a prospective study. These patients were followed at regular intervals with history, physical examination, and radiographs; American Orthopaedic Foot & Ankle Society (AOFAS) Ankle-Hindfoot Scale scores were obtained and recorded. Primary outcomes included implant survivability and functional outcomes scores. Secondary outcomes included perioperative complications such as periprosthetic or polyethylene fracture. Between 1999 and 2013, a total of 138 STAR TAAs were performed in 131 patients; 81 patients were female. The mean age at surgery was 61.5 ± 12.3 years (range, 30-88 years). The mean duration of follow-up for living patients who retained both initial components at final follow-up was 8.8±4.3 years (range 2-16.9 years). Results: The mean change in AOFAS Ankle-Hindfoot scores from preoperative to final follow-up was 36.0 ± 16.8 ( P < .0001). There were 21 (15.2%) implant failures that occurred at a mean 4.9 ± 4.5 years postoperation. Ten polyethylene components in 9 TAAs (6.5%) required replacement for fracture at an average 8.9 ± 3.3 years postoperatively. Fourteen patients died with their initial implants in place. Conclusion: This cohort of patients with true intermediate follow-up after TAA with the STAR prosthesis had acceptable implant survival, maintenance of improved patient-reported outcome scores, and low major complication rates. Level of Evidence: Level IV, case series.

Pedestrian Impedance of Turning-Movement Saturation Flow Rates: Comparison of Simulation, Analytical, and Field Observations

1997 ◽  
Vol 1578 (1) ◽  
pp. 56-63 ◽  
Author(s):  
Nagui M. Rouphail ◽  
Brian S. Eads
Keyword(s):  
United States ◽  
Empirical Data ◽  
The United States ◽  
Signalized Intersections ◽  
Urban Traffic ◽  
Analytical Models ◽  
Flow Rates ◽  
Micro Simulation ◽  
Logarithmic Relationship ◽  
Saturation Flow

TRAF-NETSIM and its successor CORSIM are comprehensive micro-simulation environments that have been widely used to model the urban traffic environment in the United States and abroad. CORSIM is employed in this study to simulate and evaluate the effects of pedestrian flows on right-turn saturation flow rates at signalized intersections. The saturation flow rates returned by CORSIM were compared with field data collected throughout the United States and with three existing analytical models in the United States, Australia, and Canada. These comparisons indicated that CORSIM models pedestrian interference with the turning vehicles more severely than the three analytical methods, but with a smaller effect than the empirical data indicate. Further, the empirical data exhibit a logarithmic relationship between saturation flow rate and opposing pedestrian volume, compared with the linear relationship used in the simulation and analytical models. Implications for the design and analysis of signalized intersections are presented.

Capacity Analysis for Fixed-Time Signalized Intersection for Non-Lane Based Traffic Condition

2009 ◽  
Vol 83-86 ◽  
pp. 904-913
Author(s):  
M. Hadiuzzaman ◽  
M. Mizanur Rahman
Keyword(s):  
Fixed Time ◽  
Signalized Intersections ◽  
Degree Of Saturation ◽  
Capacity Analysis ◽  
Delay Model ◽  
Traffic Condition ◽  
Site Specific ◽  
Study Approach ◽  
Saturation Flow ◽  
Lane Based

Capacity analysis of signalized intersections basically consists of estimating saturation flow and delay. Pre-timed signals are most commonly used in developing countries. This research deals with development of saturation flow and delay models for pre-timed signalized intersections with reference to non-lane based traffic condition prevailing in Bangladesh. In order to account non-uniformity in the static and dynamic characteristics of the vehicles passenger car unit (PCU) values for each vehicle is found out using synchronous regression technique and a range of site-specific PCU values were obtained. From this study, it has been observed that unified PCU concept does not hold good for non-lane based traffic condition and it has been recommended that the analysis should be site specific for non-lane based traffic condition. The saturation flow for each study approach was calculated using the average PCU values and multiple linear regression techniques were then used to derive predictive saturation flow models. Field delay for each approach is calculated based on HCM 2000 guidelines. It has been observed that HCM 2000 delay model consistently over estimate delay at degree of saturation more than 1.0. It has been suggested from the analysis that theoretical incremental delay (due to random arrival and over saturated queues) in HCM 2000 delay model be reduced by 70 % to better reflect field conditions in capacity analysis for non lane based traffic condition.

scholarly journals The spanning plate as an internal fixator in complex distal radius fractures – a prospective cohort study

2021 ◽  
Vol 108 (Supplement_4) ◽  
Author(s):  
R Liechti ◽  
R Babst ◽  
U Hug ◽  
B -C Link ◽  
B van de Wall ◽  
...  
Keyword(s):  
Distal Radius ◽  
The United States ◽  
Distal Radius Fractures ◽  
Outcome Analysis ◽  
Dash Score ◽  
Initial Operation ◽  
Radius Fractures ◽  
Articular Fractures ◽  
The Mean

Abstract Objective Minimal invasive temporary spanning plate (SP) fixation of the wrist has been described as an alternative treatment method in complex distal radius fractures (DRFs). The purpose of this study is to conduct an outcome analysis of all consecutive DRFs treated by SP fixation representing the so far largest published patient cohort outside the United States. Methods Indication for SP fixation included DRFs with severe metaphyseal comminution, radiocarpal luxation fractures with concomitant ligamentous injuries and very distal intra-articular fractures lacking the possibility of adequate plate anchoring. All consecutive patients undergoing SP fixation of DRFs were prospectively included in a single level I trauma centre between 01/01/2018 and 31/12/2020. Post-operative assessments included radiological, functional and patient-rated outcomes at a minimum of 12 months follow-up. Results In the mentioned timeframe, a total of 508 DRFs were treated operatively of which 28 underwent SP fixation. Average age was 58.1 years (range 22-95 years). The fracture type ranged from AO/OTA type B1.1 to C3.3 and included 8 fracture dislocations. SP removal was performed on average 3.7 months after the initial operation (range 1.4-6.5 months). The mean follow-up time was 14.5 months (range 12-24 months). Radiological evidence of fracture healing appeared on average 9.9 weeks (range 5-28 weeks) after the initial operation. One patient experienced oligosymptomatic non-union. Complications included 2 patients with tendon rupture and one patient with extensor tendon adhesions needing tenolysis at the time of plate removal leaving an overall complication rate of 12%. There was no implant failure and no infection. Mean satisfaction score was 8 (range 0-10) and mean visual analogue scale for resting pain was 0.9 (range 0-9). The mean PRWE score was 17.9 (range 0-59.5) and the mean DASH score was 16.6 (range 0-60.8). Grip strength averaged 23kg (range 4-74kg) amounting to 68% of the opposite side. Mean radial inclination, volar tilt and ulnar variance at 1 year were all within the acceptable limit predictive of symptomatic malunion. Conclusion The radiological, functional and patient-rated outcomes in this study are remarkably good considering the complexity of the included fractures. Therefore, this method represents a valuable alternative for the treatment of complex DRFs in selected patients.

Abstract 16712: Safety & Efficacy of Cryoballoon versus Radiofrequency Ablation for Atrial Fibrillation in Elderly Patients

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Tauseef Akhtar ◽  
Usama A Daimee ◽  
Bhradeev Sivasambu ◽  
Erica Hart ◽  
Joseph E Marine ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Elderly Patients ◽  
The United States ◽  
Rf Ablation ◽  
Limited Data ◽  
Multivariable Model ◽  
Major Complications ◽  
Significant Difference ◽  
The Mean

Introduction: Catheter ablation (CA) for atrial fibrillation (AF) is widely performed, with a rising proportion of patients of advanced age receiving the procedure. There are limited data describing the experience of index radiofrequency (RF) vs. cryoballoon (CB) ablation for AF among elderly patients in the United States. Hypothesis: CB ablation is associated with better outcomes in elderly patients. Methods: We conducted a retrospective analysis of patients > 75 years undergoing index AF ablation between January 2001 and March 2019 at our center. Major complications and efficacy, defined as freedom from any atrial tachyarrhythmia (ATA) lasting ≥30 seconds after 1 year of follow-up, were assessed in patients with index RF vs. CB ablation. Predictors of ATA recurrence at 1year follow-up were also evaluated. Results: In our cohort of 194 patients, the mean age was 78 + 3.1 years, 58.2% were men, and 39.4% had persistent AF. The mean left atrial (LA) diameter was 4.5 + 0.7, while mean CHA2DS2-VASc score was 3.5 + 1.2. The majority (n=149, 76.8%) underwent RF ablation. The incidence of major complications, including bleeding and cardiac tamponade, was similar in the two sub-groups (RF: 2% vs. CB: 0%, p=0.63). No significant difference in success rate at 1year follow-up was found between patients receiving RF vs. CB ablation (57.7% vs. 64.4% Figure, p=0.94). In a multivariable model adjusting for the age, sex, CHA 2 DS 2 -VASc score, AF type, and index RF vs CB ablation, only LA size was associated with ATA recurrence at 1 year follow-up with each increment of 1 cm in LA size was associated with 1.6-fold greater risk of recurrence [HR=1.59, CI: 1.05-2.41, p=0.02]. Conclusion: In elderly patients undergoing index CA for AF, RF ablation was the predominant modality with similar safety and efficacy relative to CB ablation. LA size was the significant predictor of ATA recurrence at 1year independent of index ablation modality.

Sign in / Sign up

Export Citation Format

Share Document