Framework for Investigation of Level-of-Service Criteria and Thresholds on Rural Freeways

2003 ◽  
Vol 1852 (1) ◽  
pp. 239-245 ◽  
Author(s):  
Jin-Tae Kim ◽  
Kenneth G. Courage ◽  
Scott S. Washburn ◽  
Gina Bonyani
Keyword(s):  
High Speed ◽  
Field Measurements ◽  
Level Of Service ◽  
Traffic Density ◽  
Cruise Control ◽  
Traffic Demand ◽  
Operational Conditions ◽  
Percent Time ◽  
Rural And Urban ◽  
Traffic Stream

The Highway Capacity Manual prescribes level-of-service (LOS) criteria as a function of traffic density to categorize the operational conditions of both rural and urban freeway sections. This density-based level of service is ideally suited to the assessment of urban freeways when the performance must be optimized to meet high traffic demand. There is, however, some question as to whether density is the appropriate indicator of the quality of service on rural freeways, since drivers may think more in terms of psychological or emotional comfort for freeways, which generally serve long, high-speed trips and rarely experience more than moderate congestion levels. Three specific measures are examined that have at least an intuitive relationship to the concept of driver comfort: ( a) acceleration noise, which is a measure of the physical turbulence in the traffic stream; ( b) number and duration of cruise control applications, which could serve as a general indication of driver convenience or inconvenience; and ( c) percent time spent following, which is already accepted as the basis for determining the level of service on rural two-lane highways. The three candidate measures were estimated for a hypothetical section of rural freeway by simulation, using the CORSIM model. The kinematic relationships of individual vehicles within the traffic stream were estimated by postprocessing the simulation data for each second of operation. All of the measures considered in this study have conceptual appeal. All have produced interesting and potentially usable results with respect to their relationships to traffic volume. Although the simulation results are interesting, further studies focusing on driver opinions, behavior, or field measurements, or all three, would likely be necessary to support the development and recommendation of a specific set of LOS criteria that recognizes the differences between the urban and rural freeway driving environments.

Measurement of level of service for two-lane rural highways

1982 ◽  
Vol 9 (3) ◽  
pp. 385-398 ◽  
Author(s):  
John F. Morrall ◽  
Al Werner
Keyword(s):  
High Speed ◽  
The United States ◽  
Operating Conditions ◽  
Level Of Service ◽  
Cruise Control ◽  
Highway Capacity ◽  
Long Distance ◽  
Rural Highways ◽  
Rural Highway ◽  
Highway System

Rural highway capacity, level of service, and other planning criteria are based on outdated information from the United States where the operating environment and traffic conditions are often quite different from those in Canada. Much of the information on rural two-lane highway overtaking and capacity in the 1965 Highway Capacity Manual (HCM) can be traced to data collected as long ago as 1938. Rural two-lane highway capacity and overtaking concepts in use today have remained essentially unchanged since they first appeared in the 1950 Highway Capacity Manual.This paper presents the findings of an investigation into speed–volume relations, platooning, and overtaking on the primary two-lane rural highway system in Alberta, British Columbia, and the National Parks.The principal findings are: (i) there is little relation between speed and volume over the range of volume observed — up to 1700 vehicles per hour, (ii) the average speed at 1000 vph was found to be 20–25 km/h higher than that predicted in the HCM, (iii) the backward bending portion of the speed–volume curve was not observed, (iv) speed distributions at flow rates of 1200 vph showed a marked increase in speed over that in the HCM, and (v) speed distributions of free-moving vehicles indicate a higher proportion of vehicles travelling at uniform speed.The implication of the findings is that the level of service on two-lane rural highways is much higher than that given in the HCM. This, however, is not the case on most of the primary two-lane highway system in western Canada. Despite low volumes, in the 2500–5000 average daily traffic range, drivers perceive a low level of service. This is attributed to a high proportion of long distance (over 300 km), high-speed trips, in rolling terrain with restricted sight distances, through sparsely developed territory with few intermediate stops. Thus motorists spend most of their journey travelling in high-speed platoons resulting in a high driver workload and a propensity to take risks when overtaking.The paper concludes with a recommendation that a nation-wide effort be mounted to collect speed–volume, headway, platooning, and passing data over the full range of highway operating conditions on a year-round basis. A second recommendation is that provincial highway departments in Canada investigate the concept of platooning and opportunity to overtake for evaluating their two-lane highways. More attention should be given to the education and testing of drivers in the skills of overtaking on rural highways. Also proposed is an evaluation of currently accepted, safe passing sight distances, which may be inadequate for the current operating conditions and traffic mix. Alternatives to four lanes, such as alternating passing lanes with early warning signs (to inform the driver of overtaking opportunities a specified distance ahead in order to reduce driver frustration and prevent dangerous passes), need evaluation as well. The paper concludes with a comment on the possible impact of lower speed limits and vehicle control devices, such as the cruise control, on platooning, overtaking, and level-of-service measurement.

Characteristics of Stable Rotating Stall Cells in an Axial Compressor

2017 ◽  
Author(s):  
Adam R. Hickman ◽  
Scott C. Morris
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Pressure Ratio ◽  
Pressure Sensors ◽  
Axial Compressor ◽  
Field Measurements ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Stable Operation ◽  
Double Phase

Flow field measurements of a high-speed axial compressor are presented during pre-stall and post-stall conditions. The paper provides an analysis of measurements from a circumferential array of unsteady shroud static pressure sensors during stall cell development. At low-speed, the stall cell approached a stable size in approximately two rotor revolutions. At higher speeds, the stall cell developed within a short amount of time after stall inception, but then fluctuated in circumferential extent as the compressor transiently approached a stable post-stall operating point. The size of the stall cell was found to be related to the annulus average flow coefficient. A discussion of Phase-Locked Average (PLA) statistics on flow field measurements during stable operation is also included. In conditions where rotating stall is present, flow field measurements can be Double Phase-Locked Averaged (DPLA) using a once-per-revolution (1/Rev) pulse and the period of the stall cell. The DPLA method provides greater detail and understanding into the structure of the stall cell. DPLA data indicated that a stalled compressor annulus can be considered to contained three main regions: over-pressurized passages, stalled passages, and recovering passages. Within the over-pressured region, rotor passages exhibited increased blade loading and pressure ratio compared to pre-stall values.

scholarly journals Field measurements of aerodynamic pressures in tunnels induced by high speed trains

2012 ◽  
Vol 100 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Yung-Yen Ko ◽  
Cheng-Hsing Chen ◽  
Ing-Tsang Hoe ◽  
Shin-Tsyr Wang
Keyword(s):  
High Speed ◽  
Field Measurements ◽  
High Speed Trains

scholarly journals Cooperative Adaptive Driving for Platooning Autonomous Self Driving Based on Edge Computing

2019 ◽  
Vol 29 (2) ◽  
pp. 213-225 ◽  
Author(s):  
Ben-Jye Chang ◽  
Ren-Hung Hwang ◽  
Yueh-Lin Tsai ◽  
Bo-Han Yu ◽  
Ying-Hsin Liang
Keyword(s):  
Shock Waves ◽  
Traffic Flow ◽  
Road Traffic ◽  
Edge Computing ◽  
Traffic Information ◽  
Velocity Variation ◽  
Traffic Density ◽  
Cruise Control ◽  
Safe Driving ◽  
Butterfly Effect

Abstract Cooperative adaptive cruise control (CACC) for human and autonomous self-driving aims to achieve active safe driving that avoids vehicle accidents or traffic jam by exchanging the road traffic information (e.g., traffic flow, traffic density, velocity variation, etc.) among neighbor vehicles. However, in CACC, the butterfly effect is encountered while exhibiting asynchronous brakes that easily lead to backward shock-waves and are difficult to remove. Several critical issues should be addressed in CACC, including (i) difficulties with adaptive steering of the inter-vehicle distances among neighbor vehicles and the vehicle speed, (ii) the butterfly effect, (iii) unstable vehicle traffic flow, etc. To address the above issues in CACC, this paper proposes the mobile edge computing-based vehicular cloud of the cooperative adaptive driving (CAD) approach to avoid shock-waves efficiently in platoon driving. Numerical results demonstrate that the CAD approach outperforms the compared techniques in the number of shock-waves, average vehicle velocity, average travel time and time to collision (TTC). Additionally, the adaptive platoon length is determined according to the traffic information gathered from the global and local clouds.

scholarly journals Traffic Demands Policies Effect on Congestion, Delay and Fuel Consumption

2020 ◽  
Vol 9 (5) ◽  
pp. 521-527
Keyword(s):  
Fuel Consumption ◽  
Expert Panel ◽  
Demand Management ◽  
Level Of Service ◽  
System Management ◽  
Transportation Demand ◽  
Traffic Demand ◽  
Study Case ◽  
The Government ◽  
Reduction Percentage

Traffic demands on Jordanian streets have been affected by the increasing human population and the number of vehicles. This study aims to apply transportation demand management (TDM) techniques to improve the level of service (LOS). The study employs both TDM and transportation system management (TSM). In order to investigate what type of strategies to be considered a questionnaire is used. The acceptance degrees of the TDM and TSM groups were measured via the questionnaires using SPSS version 20. The selected policies then are used on a certain location as a study case in Amman city; an intersection is connecting two urban main streets. The used policies have a reduction percentage in traffic demands which is expected throughout an expert panel. The results show that delay and fuel consumption are indeed reduced; however, this does not lead to any considerable improvement in the LOS. The LOS was enhanced when the reduction in traffic demand reached 20% with an increase in capacity achieved by adding 3 new lanes. The fuel consumption and delays were measured to be about 35% less with growth rate of 8% for the coming five years. This study is expected to help popularize TDM policies in place of other solutions so that inexpensive measures can be adopted by the government.

Uncertainty in Operational Analysis of Two-Lane Highways

2002 ◽  
Vol 1802 (1) ◽  
pp. 105-114 ◽  
Author(s):  
R. Tapio Luttinen
Keyword(s):  
Input Data ◽  
Travel Speed ◽  
Level Of Service ◽  
Model Parameters ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Operational Analysis ◽  
Percent Time ◽  
Different Types ◽  
Percent Time Spent Following

The Highway Capacity Manual (HCM) 2000 provides methods to estimate performance measures and the level of service for different types of traffic facilities. Because neither the input data nor the model parameters are totally accurate, there is an element of uncertainty in the results. An analytical method was used to estimate the uncertainty in the service measures of two-lane highways. The input data and the model parameters were considered as random variables. The propagation of error through the arithmetic operations in the HCM 2000 methodology was estimated. Finally, the uncertainty in the average travel speed and percent time spent following was analyzed, and four approaches were considered to deal with uncertainty in the level of service.

Design Gap Acceptance for Right-Turning Vehicles Based on Vehicle Acceleration Capabilities

2015 ◽  
Vol 2521 (1) ◽  
pp. 12-21 ◽  
Author(s):  
Essam Dabbour
Keyword(s):  
Regression Models ◽  
Field Measurements ◽  
Data Logger ◽  
Sight Distance ◽  
Design Guide ◽  
Traffic Stream ◽  
Cross Traffic ◽  
Vehicle Acceleration ◽  
The Cross ◽  
The Right

The current geometric design guide provides a methodology to analyze intersection sight distance for right-turning vehicles at signalized and two-way stop-controlled intersections based on the gaps accepted by the majority of drivers as measured from the field. That methodology is based mainly on driver behavior without considering the actual capabilities of the turning vehicle when accelerating from rest to the speed of the cross-traffic stream. This paper introduced the new design gap concept, which was based on the actual distance and time needed for the turning vehicle to accelerate to the same speed of the cross-traffic stream to avoid a collision. The acceleration capabilities of the turning vehicle were based on field measurements collected by GPS data logger devices that recorded the positions and instantaneous speeds of different turning vehicles at 1-s intervals; based on that, regression models were developed to establish an acceleration profile for a typical vehicle turning to the right from rest. Design tables were provided to help road designers select appropriate design gaps needed for different design speeds and grades of the crossing roadways. In comparison to the new design gaps, the measured gaps used in design were found to be generally inadequate. After implementation of the newly developed design gaps, turning drivers will potentially be able to accelerate comfortably without forcing other drivers in the cross-traffic stream to reduce their speeds or to change lanes to avoid colliding with turning vehicles.

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