scholarly journals Evaluating the Impacts of Speed Limit Increases on Rural Two-Lane Highways Using Quantile Regression

2021 ◽  
pp. 036119812110197
Author(s):  
Md Shakir Mahmud ◽  
Nischal Gupta ◽  
Babak Safaei ◽  
Hisham Jashami ◽  
Timothy J. Gates ◽  
...  
Keyword(s):  
Quantile Regression ◽  
Spillover Effects ◽  
Speed Limit ◽  
Passenger Cars ◽  
Cross Sectional ◽  
Speed Limits ◽  
Site Specific ◽  
Rural Highways ◽  
Speed Selection ◽  
Numerous Site

Understanding speed selection behavior of drivers following speed limit increases is critically important. To date, the literature has largely focused on freeways and the effects of speed limit changes on two-lane highways remains under researched. Prior research has generally focused on changes to mean speeds, although the speeds of both the highest and lowest drivers are also of great interest. This study investigates trends in free-flow travel speeds following 2017 legislation that increased the posted speed limit from 55 to 65 mph on 943 mi of rural highways in Michigan. Speed data were collected for over 46,000 drivers at 67 increase segments where speed limit increased and 28 control segments where speed limits remained unchanged, before and during each of the two successive years following the speed limit increases. Site-specific traffic, geometric, and cross-sectional information was also collected. Impacts of the speed limit increases on the 15th, 50th, and 85th percentile speeds were evaluated using quantile regression. Separate analyses were conducted for passenger cars and heavy vehicles. Locations where the speed limits were raised experienced increases in travel speeds ranging from 2.8 to 4.8 mph. The control sites experienced marginal changes in speeds, which suggests that any spillover effects of the higher speed limits have been limited. Significant differences were observed across the quantiles with respect to the effects of the speed limit increases, as well as numerous site-specific variables of interest. The results provide important insights about the nature of driver speed selection and the impacts of speed limit increases.

scholarly journals Evaluating the Impacts of Speed Limit Increases on Rural Two-Lane Highways using Quantile Regression

2021 ◽  
Author(s):  
Shakir Mahmud ◽  
Nischal Gupta ◽  
Babak Safaei ◽  
Hisham Jashami ◽  
Timothy Gates ◽  
...  
Keyword(s):  
Quantile Regression ◽  
Spillover Effects ◽  
Speed Limit ◽  
Passenger Cars ◽  
Cross Sectional ◽  
Speed Limits ◽  
Site Specific ◽  
Rural Highways ◽  
Speed Selection ◽  
Numerous Site

Understanding speed selection behavior of drivers following speed limits increases is critically important. To date, the literature has largely focused on freeways and the effects of speed limit changes on two-lane highways remains under researched. Prior research has generally focused on changes to mean speeds, though the speeds of both the highest and lowest drivers are also of great interest. This study investigates trends in free-flow travel speeds following 2017 legislation that increased the posted speed limit from 55 to 65 mph on 943 miles of rural highways in Michigan. Speed data were collected for over 46,000 drivers at 67 increase segments where speed limit increased and 28 control segments, where speed limits remained unchanged, before and during each of the two successive years following the speed limit increases. Site-specific traffic, geometric, and cross-sectional information was also collected. Impacts of the speed limit increases on the 15th, 50th, and 85th percentile speeds were evaluated using quantile regression. Separate analyses were conducted for passenger cars and heavy vehicles. Locations where the speed limits were raised experienced increases in travel speeds ranging from 3.8 to 5.1 mph. The control sites experienced marginal changes in speeds, which suggests any spillover effects of the higher speed limits have been limited. Significant differences were observed across the quantiles with respect to the effects of the speed limit increases, as well as numerous site-specific variables of interest. The results provide important insights as to the nature of driver speed selection and the impacts of speed limit increases.

Short-Term Evaluation of Transition from Differential to Uniform Speed Limit for Trucks and Buses on Two-Lane Highways

2017 ◽  
Vol 2637 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Raha Hamzeie ◽  
Bijan Vafaei ◽  
Jonathan J. Kay ◽  
Peter T. Savolainen ◽  
Timothy J. Gates
Keyword(s):  
Field Studies ◽  
Speed Limit ◽  
Short Term ◽  
Immediate Feedback ◽  
Speed Limits ◽  
Rural Highways ◽  
Short Term Evaluation ◽  
Term Evaluation ◽  
Operational Issues ◽  
Differential Speed

As of November 2016, Montana was the only state to maintain a differential speed limit on two-lane two-way rural highways, with a daytime statutory speed limit of 70 mph for cars and light trucks and 60 mph for trucks exceeding a 1-ton payload capacity. Although differential speed limits are common on freeways, the use of differential limits on two-lane roadways presents unique safety and operational issues because of passing limitations and the resultant platooning that occurs. Given these concerns, the speed limit was changed from the differential 70 mph to 60 mph speed limit to a uniform 65 mph limit for all vehicles along 55 mi of two-lane highway in April 2013. This study evaluated the short-term operational and safety impacts associated with this transition. Given the limited time period over which data were available following the speed limit change, surrogate safety measures were investigated to provide immediate feedback as to these impacts. A series of field studies was performed on two-lane rural highways in Montana, which predominantly possessed the 70 mph to 60 mph differential speed limit, as well as on selected locations along the 55 mi where the uniform speed limit was implemented. The locations with 65 mph speed limits generally exhibited shorter platoon lengths and less high-risk passing behavior. Overall, the preliminary findings provide some general support for transitioning to a uniform 65 mph speed limit on two-lane rural highways.

Setting Speed Limits on Kansas Two-Lane Highways: Neuronet Approach

2000 ◽  
Vol 1708 (1) ◽  
pp. 20-27 ◽  
Author(s):  
Yacoub M. Najjar ◽  
Robert W. Stokes ◽  
Eugene R. Russell
Keyword(s):  
Neural Network ◽  
Back Propagation ◽  
Field Studies ◽  
Back Propagation Neural Network ◽  
Speed Limit ◽  
Speed Limits ◽  
Rural Highways ◽  
Resource Limitations ◽  
Traffic Volumes ◽  
The Relationship

Recent federal legislation allowing states to set their own speed limits on highways, as well as increases in the number of requests from citizens and neighborhood groups to implement actions to reduce “excessive” speeding on their streets and highways, has created considerable debate about and scrutiny of the appropriate speed limits that should be posted on state highways. Various speed studies have indicated that sensible and cautious drivers will most likely drive at the speed dictated by roadway and traffic conditions rather than relying on a posted speed limit. To incorporate roadway characteristics and traffic volumes into the selection of the most appropriate (i.e., comfortable, safe, and efficient) speed limit, actual engineering field speed studies are carried out. Generally, the 85th percentile speed at which the drivers surveyed are driving is selected as a primary factor in determining the posted speed limit. Carrying out such field studies for all highway sections is a costly and time-consuming process. Therefore, characterizing the relationship between the 85th percentile speed and the roadway characteristics will assist in selecting the most appropriate posted speed limit on highway sections where field surveying is difficult due to resource limitations. A back-propagation neural network is used to extract the relationship between roadway characteristics and 85th percentile speed. The developed neural-network-based speed model was found to perform satisfactorily for characterization of speed on Kansas two-lane, uninterrupted-flow rural highways and for quantifying the influence of prevailing roadway characteristics on the anticipated 85th percentile speed.

Raising Speed Limits on Rural Highways: Process for Identification of Candidate Nonfreeway Segments

2017 ◽  
Vol 2618 (1) ◽  
pp. 58-68 ◽  
Author(s):  
Jonathan J. Kay ◽  
Timothy J. Gates ◽  
Peter T. Savolainen
Keyword(s):  
Selection Criteria ◽  
Primary Objective ◽  
Segment Length ◽  
Speed Limit ◽  
Speed Limits ◽  
Rural Highways ◽  
Speed Reduction ◽  
Safety Research ◽  
Lane Width ◽  
Design Speed

Speed limits on rural highways have recently been on an upward trend nationwide as 25 states have increased speed limits on such roadways between 2011 and 2016. In January 2017, Michigan House Bill 4423 (Public Act 445) was signed into law, which required speed limits to be raised from 55 to 65 mph on at least 900 mi of Michigan’s state-maintained nonfreeways. The specific highway segments were to be selected by the Michigan Department of Transportation (DOT) within 1 year of enactment on the basis of an assessment of travel speeds and safety. Research was undertaken to develop a process to select candidate highway segments for speed limit increases in Michigan. The primary objective was to identify rural highway segments with comparatively low safety risks for which costly geometric upgrades, specifically horizontal or vertical realignment, would be avoided. Ultimately, 12 factors and associated selection criteria were used to identify the candidate segments. These factors included segment length, total crash rate, injury crash rate, severe (fatal and A-injuries) crash rate, horizontal curvature, speed reduction zones, no-passing zones, schools (kindergarten through eighth grade), driveway density, lane width, paved shoulder width, and signalized intersections. Application of the candidate selection criteria to the Michigan DOT nonfreeway network yielded 772.8 centerline miles along 33 candidate segments, which represented approximately one-eighth of the network mileage currently posted at 55 mph. To avoid substantial geometric upgrade costs, speed limit increases were specifically not recommended for segments that would require horizontal or vertical realignment to achieve design speed compliance with the increased speed limit.

Site-Specific Low Angle Plasma FIB Milling for Cross-Sectional Electrical Characterization

2019 ◽  
Author(s):  
Chuan Zhang ◽  
Jane Y. Li ◽  
John Aguada ◽  
Howard Marks
Keyword(s):  
Cross Section ◽  
Focused Ion Beam ◽  
Electrical Characteristic ◽  
Preparation Method ◽  
Ion Beam ◽  
Grazing Angle ◽  
Electrical Characterization ◽  
Sample Preparation Method ◽  
Cross Sectional ◽  
Site Specific

Abstract This paper introduces a novel sample preparation method using plasma focused ion-beam (pFIB) milling at low grazing angle. Efficient and high precision preparation of site-specific cross-sectional samples with minimal alternation of device parameters can be achieved with this method. It offers the capability of acquiring a range of electrical characteristic signals from specific sites on the cross-section of devices, including imaging of junctions, Fins in the FinFETs and electrical probing of interconnect metal traces.

scholarly journals Comparison of healthcare resource utilization and medical costs between patients with seropositive and seronegative rheumatoid arthritis

2021 ◽  
Vol 13 ◽  
pp. 1759720X2110248
Author(s):  
Hyoungyoung Kim ◽  
Soo-Kyung Cho ◽  
Seongmi Choi ◽  
Seul Gi Im ◽  
Sun-Young Jung ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Quantile Regression ◽  
Healthcare Utilization ◽  
Medical Costs ◽  
Healthcare Resource Utilization ◽  
Medical Utilization ◽  
Cross Sectional ◽  
Direct Medical Costs ◽  
Using Data ◽  
Sectional Analysis

Objectives: To compare healthcare utilization and medical costs between patients with seronegative (SN) and seropositive (SP) rheumatoid arthritis (RA). Methods: We conducted a nationwide population study using the Korean health insurance claims database in 2016. We divided patients with RA into SN and SP groups and compared healthcare utilization including medications, medical utilization, and direct medical costs for 1 year between the groups in a cross-sectional analysis. Differences in costs between patients with SPRA and SNRA were assessed using the quantile regression model. We performed longitudinal analysis using data from 2012 and 2016 to examine changes over time. Results: A total of 103,815 SPRA and 75,809 SNRA patients were included in the analyses. The SPRA group used significantly more methotrexate (73.2% versus 30.3%) and biologic agents (7.9% versus 2.9%) than the SNRA group. The number of RA-related outpatient visits [6.0 ± 3.7 versus 4.4 ± 4.0 times/year, standardized difference (SD) = 0.41] and annual medical costs per patient ($1027 versus $450/year, SD = 0.25) were higher in the SPRA group than the SNRA group. Quantile regression results indicated that the incremental cost of seropositivity on total medical costs of RA patients gradually increased as medical costs approached the upper quantile. The annual direct medical costs for each patient between 2012 and 2016 increased in both groups: by 25.1% in the SPRA group and 37.6% in the SNRA group. Conclusion: Annual RA-related direct medical costs and RA-related healthcare utilization per patient are higher in patients with SPRA than those with SNRA.

scholarly journals Ethnicity-Specific Normative Models of Quadruple Test as a Screening Test for Down Syndrome

Medicina ◽  
2021 ◽  
Vol 57 (7) ◽  
pp. 651
Author(s):  
Praetip Praikaew ◽  
Kuntharee Traisrisilp ◽  
Chanane Wanapirak ◽  
Ratanaporn Sekararithi ◽  
Theera Tongsong
Keyword(s):  
Quantile Regression ◽  
Gestational Age ◽  
Cross Sectional Study ◽  
Serum Biomarkers ◽  
Rank Test ◽  
Maternal Weight ◽  
Cross Sectional ◽  
Inhibin A ◽  
Thai Women ◽  
Normative Models

Background and Objectives: To establish normative models for median levels of serum biomarkers of the second trimester quad test (alpha-fetoprotein: AFP; free beta-human gonadotropins: hCG; inhibin-A; and unconjugated estriol: uE3) specific to Thai women and to compare multiples of the median (MoMs) derived from ethnicity-specific models and those derived from Caucasian models with ethnic correction. Materials and Methods: A cross-sectional study was undertaken in a tertiary, medical teaching center among low-risk pregnant Thai women between 14 and 21 weeks of gestation to measure the levels of the four serum biomarkers. The measured values of each biomarker were analyzed using the multivariable factorial polynomial technique for quantile regression as a function of gestational age and maternal weight. Results: The Thai-specific normative models for the four biomarkers were generated and available for use. The MoMs of all individuals generated from our models were significantly different from conventional (Caucasian) models with ethnic correction (Wilcoxon signed-rank test; p < 0.0001 for all biomarkers). The MoMs of AFP and hCG from both methods were in agreement, but those from Thai-specific models were significantly higher. However, those of inhibin-A and uE3 were markedly different and ethnic correction was unlikely to be useful. Conclusions: The Thai-specific normative models of the quad test as a function of gestational age and maternal weight were constructed using multivariable factorial polynomial models, better than simple quantile regression or log-linear regression used in earlier decades. The analysis of MoMs supports the use of ethnicity-specific models instead of Caucasian models with ethnic correction.

scholarly journals European birds adjust their flight initiation distance to road speed limits

2013 ◽  
Vol 9 (5) ◽  
pp. 20130417 ◽  
Author(s):  
Pierre Legagneux ◽  
Simon Ducatez
Keyword(s):  
Habitat Structure ◽  
Territory Size ◽  
Speed Limit ◽  
Vehicle Speed ◽  
Flight Initiation Distance ◽  
Speed Limits ◽  
Behavioural Responses ◽  
Road Speed ◽  
Flight Initiation ◽  
Local Speed

Behavioural responses can help species persist in habitats modified by humans. Roads and traffic greatly affect animals' mortality not only through habitat structure modifications but also through direct mortality owing to collisions. Although species are known to differ in their sensitivity to the risk of collision, whether individuals can change their behaviour in response to this is still unknown. Here, we tested whether common European birds changed their flight initiation distances (FIDs) in response to vehicles according to road speed limit (a known factor affecting killing rates on roads) and vehicle speed. We found that FID increased with speed limit, although vehicle speed had no effect. This suggests that birds adjust their flight distance to speed limit, which may reduce collision risks and decrease mortality maximizing the time allocated to foraging behaviours. Mobility and territory size are likely to affect an individuals' ability to respond adaptively to local speed limits.

scholarly journals Do speed cameras reduce speeding in urban areas?

2015 ◽  
Vol 31 (suppl 1) ◽  
pp. 208-218
Author(s):  
Daniele Falci de Oliveira ◽  
Amélia Augusta de Lima Friche ◽  
Dário Alves da Silva Costa ◽  
Sueli Aparecida Mingoti ◽  
Waleska Teixeira Caiaffa
Keyword(s):  
Observational Study ◽  
Urban Areas ◽  
Associated Factors ◽  
Cell Phones ◽  
Speed Limit ◽  
Structural Interventions ◽  
Speed Limits

Abstract This observational study aimed to estimate the prevalence of speeding on urban roadways and to analyze associated factors. The sample consisted of 8,565 vehicles circulating in areas with and without fixed speed cameras in operation. We found that 40% of vehicles 200 meters after the fixed cameras and 33.6% of vehicles observed on roadways without speed cameras were moving over the speed limit (p < 0.001). Motorcycles showed the highest recorded speed (126km/h). Most drivers were men (87.6%), 3.3% of all drivers were using their cell phones, and 74.6% of drivers (not counting motorcyclists) were wearing their seatbelts. On roadway stretches without fixed speed cameras, more women drivers were talking on their cell phones and wearing seatbelts when compared to men (p < 0.05 for both comparisons), independently of speed limits. The results suggest that compliance with speed limits requires more than structural interventions.

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