Design Guidance for J-Turns on Rural High-Speed Expressways

2017 ◽  
Vol 2618 (1) ◽  
pp. 69-77 ◽  
Author(s):  
Boris Claros ◽  
Zhongyuan Zhu ◽  
Praveen Edara ◽  
Carlos Sun
Keyword(s):  
High Speed ◽  
Road Traffic ◽  
Simulation Analysis ◽  
Major Road ◽  
Crash Rates ◽  
Design Variables ◽  
Minor Road ◽  
Safety Effect ◽  
Calibrated Simulation ◽  
Crash Types

Owing to the J-turn’s safety effectiveness, it has become a viable alternative to replace high-crash, two-way, stop-controlled intersections on high-speed expressways. National guidance on the design of J-turns on high-speed highways is limited. What is the safety effect of spacing between the intersection and the U-turn? Under what circumstances is the provision of acceleration lanes recommended? This study answered these questions through a safety assessment on the basis of ( a) an examination of crashes that occurred at 12 J-turn sites in Missouri and ( b) a simulation-based assessment of the effect of various design variables and traffic flows. The crash review revealed the proportions of the five most frequently occurring crash types at J-turn sites: ( a) major road sideswipe (31.6%), ( b) major road rear-end (28.1%), ( c) minor road rear-end (15.8%), ( d) loss of control (14%), and ( e) merging from U-turn (10.5%). The crash rates, accounting for exposure, decreased with the increase in the spacing to the U-turn for sideswipe and rear-end crashes; J-turns with a spacing of 1,500 ft or greater experienced the lowest crash rates. The crash rates were lower for J-turn sites with acceleration lanes for minor road traffic merging onto the major road than for sites without acceleration lanes. A calibrated simulation model analysis revealed that the presence of acceleration lanes reduced conflicts for all volumes and designs, including low volumes. The simulation analysis also reinforced the crash analysis results that safety improved with an increase in spacing between the main intersection and the U-turn.

scholarly journals Surrogate measures for evaluating new signage and intersection designs

2016 ◽  
Author(s):  
◽  
Zhongyuan Zhu
Keyword(s):  
Case Studies ◽  
Simulation Analysis ◽  
Work Zone ◽  
Major Road ◽  
Crash Data ◽  
Design Variables ◽  
Minor Road ◽  
Alternative Designs ◽  
The Impact

Transportation agencies faced with the challenge of enhancing safety on roadways are looking for alternative solutions to designing roads and signage. When deciding whether the alternative design is superior to the traditional one, decision makers need methods and quantitative data to evaluate these alternatives. This dissertation provides two accessible methods to compare different alternative designs and illustrates them using case studies. The first method involves using speed-based statistical measures that are extracted from video-based traffic surveillance. This method was more accurate in collecting vehicle speeds than the speeds extracted from video-based data collection systems. It was then utilized to evaluate the effectiveness of an alternative merge sign in work zones. This alternative sign consists of an arrow pointing the merge direction and text describing the lane closure, while MUTCD sign is graphical. The case study measured driver behavior characteristics including speeds and open lane occupancies. The results indicate that open lane occupancy was higher for the test sign in comparison to the MUTCD sign upstream of the merge sign. The occupancy values at different distances between the merge sign and the taper were similar for both the test and MUTCD signs, but the test sign encouraged up to 11% more cars to be in the open lane immediately upstream of the merge sign. Passenger cars stayed in the closed lane longer, or closer to the taper, than trucks. The merging behavior of truck drivers did not vary significantly with the type of merge sign deployed in the work zone. The analysis of speed characteristics did not reveal substantial differences between the two sign configurations. The mean speeds with the MUTCD configuration were 1.3 mph and 2 mph lower than the test configuration at the merge sign and taper locations, respectively. The second method utilizes microscopic traffic simulation to evaluate alternative designs. This method is ideal for projects where video monitoring of the entire study of interest is not feasible. Evaluating alternative designs with crash data usually requires a long time span to build the facility and record crash data over at least one year after the facility has been open to traffic. In addition to that, new facility needs to be built or altered if other design features are to be tested. With microscopic simulation, the time cost for the study is greatly shortened and different design aspects can be tested in a risk-free environment. Two case studies are presented to illustrate this simulation method. The first case study involves a work zone while the second case study focuses on evaluating a J-turn intersection design. The spacing of U-turn and the inclusion of acceleration and deceleration lanes were evaluated, in the J-turn study. A simulation analysis was conducted to study the impact of different design variables on the safety of J-turns. A base simulation model was created and calibrated using field data collected in a previous Missouri Department of Transportation (MoDOT) project on J-turns. The calibrated model was then used to study various combinations of major road and minor road volumes and design variables. The simulation analysis helped develop guidance on recommended spacing for various major road and minor road volume scenarios. For all the studied scenarios, the presence of acceleration lane resulted in significantly fewer conflicts. Thus, acceleration lanes are recommended for all J-turn designs, including lower volume sites. Second, while U-turn spacing between 1000 feet and 2000 feet was found to be sufficient for low volume combinations, a spacing of at least 1500 feet and 2000 feet are recommended for medium and high volumes, respectively.

Delays to road traffic at an intersection

1964 ◽  
Vol 1 (2) ◽  
pp. 297-310 ◽  
Author(s):  
G. F. Yeo ◽  
B. Weesakul
Keyword(s):  
Road Traffic ◽  
Partial Solution ◽  
Major Road ◽  
Gap Acceptance ◽  
Road Vehicle ◽  
Mean Delay ◽  
Minor Road ◽  
The Mean ◽  
Stationary Waiting Time ◽  
A Minor

A model for road traffic delays at intersections is considered where vehicles arriving, possibly in bunches, in a Poisson process in a one way minor road yield right of way to traffic, which forms alternate bunches and gaps, in a major road. The gap acceptance times are random variables, and depend on whether or not a minor road vehicle is immediately following another minor road vehicle into the intersection or not.The transforms of the stationary waiting time and queue size distributions, and the mean stationary delay, for minor road vehicles are obtained by substitution of determined service time distributions into results for a generalisation of the M/G/1 queueing system. Some numerical results are given to illustrate the increase in the mean delay for variable gap acceptance times for a Borel-Tanner distribution of major road traffic, and a partial solution is given for a two way major road.

Gap-acceptance in road traffic

1968 ◽  
Vol 5 (1) ◽  
pp. 84-92 ◽  
Author(s):  
A. G. Hawkes
Keyword(s):  
Simple Model ◽  
Service Time ◽  
Time Distribution ◽  
Road Traffic ◽  
Service Time Distribution ◽  
Major Road ◽  
Gap Acceptance ◽  
Road Vehicles ◽  
Minor Road ◽  
Acceptance Function

We find the distribution of delay to minor road vehicles waiting to merge or cross a single stream of major road traffic. The decision to cross is taken on the basis of a gap-acceptance function. The model turns out to be a simple queueing problem in which a customer finding an empty queue has a different service time distribution from queueing customers. The key to this representation is given in Section 3. Some numerical results in Section 6 indicate that in most circumstances a simple model will give adequate results.

The capacity of an intersection with non-stationary traffic

1976 ◽  
Vol 13 (02) ◽  
pp. 418-422
Author(s):  
Helmut Wegmann
Keyword(s):  
Road Traffic ◽  
Intensity Function ◽  
Major Road ◽  
Homogeneous Case ◽  
Homogeneous Poisson Process ◽  
Periodic Intensity ◽  
Minor Road ◽  
Traffic Stream ◽  
A Minor ◽  
Non Homogeneous Poisson Process

The average number of vehicles being able to enter an intersection per time unit from a minor road with a stop or yield sign — the capacity of the intersection — depends on the density of the traffic stream on the major road. In case the time-process of the major road traffic at the intersection is a non-homogeneous Poisson process with a periodic intensity function the capacity is calculated and compared with the capacity in the homogeneous case.

The capacity of an intersection with non-stationary traffic

1976 ◽  
Vol 13 (2) ◽  
pp. 418-422 ◽  
Author(s):  
Helmut Wegmann
Keyword(s):  
Road Traffic ◽  
Intensity Function ◽  
Major Road ◽  
Homogeneous Case ◽  
Homogeneous Poisson Process ◽  
Periodic Intensity ◽  
Minor Road ◽  
Traffic Stream ◽  
A Minor ◽  
Non Homogeneous Poisson Process

The average number of vehicles being able to enter an intersection per time unit from a minor road with a stop or yield sign — the capacity of the intersection — depends on the density of the traffic stream on the major road. In case the time-process of the major road traffic at the intersection is a non-homogeneous Poisson process with a periodic intensity function the capacity is calculated and compared with the capacity in the homogeneous case.

Gap-acceptance in road traffic

1968 ◽  
Vol 5 (01) ◽  
pp. 84-92 ◽  
Author(s):  
A. G. Hawkes
Keyword(s):  
Simple Model ◽  
Service Time ◽  
Time Distribution ◽  
Road Traffic ◽  
Service Time Distribution ◽  
Major Road ◽  
Gap Acceptance ◽  
Road Vehicles ◽  
Minor Road ◽  
Acceptance Function

We find the distribution of delay to minor road vehicles waiting to merge or cross a single stream of major road traffic. The decision to cross is taken on the basis of a gap-acceptance function. The model turns out to be a simple queueing problem in which a customer finding an empty queue has a different service time distribution from queueing customers. The key to this representation is given in Section 3. Some numerical results in Section 6 indicate that in most circumstances a simple model will give adequate results.

Assessing Heavy Vehicle Impacts on Operation of Rural At-Grade Intersections in Brazil

1996 ◽  
Vol 1555 (1) ◽  
pp. 83-90
Author(s):  
José Reynaldo Setti ◽  
Sergio Henrique Demarchi
Keyword(s):  
Simulation Model ◽  
Road Traffic ◽  
Vehicle Classification ◽  
Heavy Vehicle ◽  
Major Road ◽  
Passenger Cars ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Minor Road ◽  
Time Required

A simulation model was used to assess the impacts of trucks on the capacity of rural, at-grade, stop-controlled intersections in Brazil. The major differences between Brazilian and North American vehicles and intersections are discussed and a system for vehicle classification that reflects the characteristics of Brazilian vehicles is proposed. The proposed simulation model assumes that there is an endless queue of vehicles that approaches the intersection from the minor road. Gaps in the major road traffic flow are generated using a displaced exponential distribution. Crossing times and gap acceptance are modeled by logit models fitted for each vehicle category. Heavy vehicle equivalence factors are calculated as the average number of passenger cars that are able to cross the major road during the time required by each truck type to execute the same maneuver. The capacity estimates obtained with the model are similar to values calculated with Siegloch's model, which is the basis for the Highway Capacity Manual (HCM) procedure. The equivalence factors estimated for trucks are considerably higher than those suggested in the HCM for most truck categories.

Delays to road traffic at an intersection

1964 ◽  
Vol 1 (02) ◽  
pp. 297-310 ◽  
Author(s):  
G. F. Yeo ◽  
B. Weesakul
Keyword(s):  
Road Traffic ◽  
Partial Solution ◽  
Major Road ◽  
Gap Acceptance ◽  
Road Vehicle ◽  
Mean Delay ◽  
Minor Road ◽  
The Mean ◽  
Stationary Waiting Time ◽  
A Minor

A model for road traffic delays at intersections is considered where vehicles arriving, possibly in bunches, in a Poisson process in a one way minor road yield right of way to traffic, which forms alternate bunches and gaps, in a major road. The gap acceptance times are random variables, and depend on whether or not a minor road vehicle is immediately following another minor road vehicle into the intersection or not. The transforms of the stationary waiting time and queue size distributions, and the mean stationary delay, for minor road vehicles are obtained by substitution of determined service time distributions into results for a generalisation of the M/G/1 queueing system. Some numerical results are given to illustrate the increase in the mean delay for variable gap acceptance times for a Borel-Tanner distribution of major road traffic, and a partial solution is given for a two way major road.

Dynamic Analysis of DVG 850 High-Speed Machining Center

2012 ◽  
Vol 487 ◽  
pp. 203-207
Author(s):  
Gong Xue Zhang ◽  
Xiao Kai Shen
Keyword(s):  
High Speed ◽  
Simulation Analysis ◽  
Response Analysis ◽  
Improved Method ◽  
Analysis Software ◽  
Element Analysis ◽  
Harmonic Response ◽  
Machining Center ◽  
Calculation Results ◽  
Harmonic Response Analysis

Purpose, with the application of workbench finite element analysis software, get the analysis results of DVG 850 high-speed vertical machining center via the modal analysis and harmonic response analysis. Use the calculation results for reference, put forward the improved method, and prove the credibility of the simulation analysis by testing DVG 850 prototype.

scholarly journals Study on the High-Speed Milling Performance of High-Volume Fraction SiCp/Al Composites

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4143
Author(s):  
Youzheng Cui ◽  
Shenrou Gao ◽  
Fengjuan Wang ◽  
Qingming Hu ◽  
Cheng Xu ◽  
...  
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Volume Fraction ◽  
Simulation Analysis ◽  
Cutting Temperature ◽  
High Volume ◽  
Cutting Parameters ◽  
High Volume Fraction ◽  
High Wear Resistance ◽  
Element Analysis

Compared with other materials, high-volume fraction aluminum-based silicon carbide composites (hereinafter referred to as SiCp/Al) have many advantages, including high strength, small change in the expansion coefficient due to temperature, high wear resistance, high corrosion resistance, high fatigue resistance, low density, good dimensional stability, and thermal conductivity. SiCp/Al composites have been widely used in aerospace, ordnance, transportation service, precision instruments, and in many other fields. In this study, the ABAQUS/explicit large-scale finite element analysis platform was used to simulate the milling process of SiCp/Al composites. By changing the parameters of the tool angle, milling depth, and milling speed, the influence of these parameters on the cutting force, cutting temperature, cutting stress, and cutting chips was studied. Optimization of the parameters was based on the above change rules to obtain the best processing combination of parameters. Then, the causes of surface machining defects, such as deep pits, shallow pits, and bulges, were simulated and discussed. Finally, the best cutting parameters obtained through simulation analysis was the tool rake angle γ0 = 5°, tool clearance angle α0 = 5°, corner radius r = 0.4 mm, milling depth ap = 50 mm, and milling speed vc= 300 m/min. The optimal combination of milling parameters provides a theoretical basis for subsequent cutting.

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