Nemzetközi szemle: Január

Az utazási igény bizonytalanságának bevonása és értékelése a közlekedési beruházások jóváhagyásánál

Incorporating and assessing travel demand uncertainty in transport investment appraisals
Szerző(k):
A. Byett, A. Grimes, J. Laird, P. Roberts
Taupo, Motu, University of Leeds, QTP Limited, New Zealand
Terjedelem: 170 oldal

Uncertainty is pervasive when it comes to transport investment decisions. While it is natural to improve the traffic forecasts that inform such decisions, it is also important to acknowledge fundamental uncertainty exists about the future. Consequently, a process is required that acknowledges and addresses these uncertainties as part of improving investment decisions. This paper explores the uncertainties within transport modelling and the ways flexibility in the face of uncertainty can add value to a transport project. Insight into value is revealed by way of examples of real options. Likewise examples of adaptive management are explored. A process is recommended that explores the nature of the key uncertainties pertaining to a transport investment and actively searches for robust solutions in the face of uncertainties. This process transparently sets the trade-offs inherent in alternative solutions in front of decision makers.

 

A geoműanyagok burkolat teljesítményre gyakorolt hatásának számszerűsítése

Quantifying the Influence of Geosynthetics on Pavement Performance
Szerző(k):
R. Luo, F. Gu, X. Luo, R.L. Lytton, E.Y. Hajj, R.V. Siddharthan, S. Elfass, M. Piratheepan, S. Pournoman
The Texas A&M University System, University of Nevada, USA
Terjedelem: 841 oldal

A well-designed LST testing protocol with extensive instrumentations was conducted on flexible and rigid pavements using an 8-ft-diameter by 6-ft-high circular steel tank. The implemented testing program differed from previous studies, which traditionally assessed the influence of the base reinforcement on pavement performance under repetitive surface loading until failure. Instead, the experimental program focused on the following distinctive characteristics of the geosynthetic, which were essential for proper modeling of the geosynthetic material for base reinforcement, and ultimately for enhanced predictions of the performance of pavements with geosynthetic-reinforced base courses: the stress distributions across the geosynthetic under dynamic loading in both the AC and PCC pavements; the strain measurements in the geosynthetic and at the bottom of the surface layer
(AC or PCC) under dynamic loading; the deformed shape of the geosynthetic and the potential slippage at the geosynthetic and the unbound aggregate material interface under dynamic loading; the potential slippage between the bottom of the PCC slab and the supporting CAB layer at the edge of the loaded slab.

 

A betontábla és az alatta fekvő réteg kölcsönhatásának bevonása a beton burkolat elemzési folyamatba

Incorporating Slab/Underlying Layer Interaction into the Concrete Pavement Analysis Procedures
Szerző(k):
L. Khazanovich, D. Tompkins
University of Minnesota, USA
Terjedelem: 279 oldal

The interaction between the concrete slab and the base layer is a complex phenomenon affecting long-term performance of concrete pavements. In this study, modeling of the slab-base interaction in the AASHTO M-E procedure for rigid pavement design was evaluated. It was found that the AASHTO M-E accounts for slab-base interaction through adjustments to the subgrade support (modulus of subgrade reaction), flexural stiffness of the pavement, load transfer efficiency of jointed plain pavements, and CRCP crack spacing distributions. Sensitivity studies of the AASHTO M-E performance models and comparisons with LTPP pavement performance data were conducted. Many complications in the performance models were identified, and thus modification of the AASHTO M-E models extended beyond changes to the bond-no bond condition for the slab-base interface. For example, it was found that modeling of JPCP projects with stiff, fully bonded base layers resulted in unrealistically low damage and predicted cracking levels. The study led to the proposed modification of the AASHTO M-E procedure to account for slab-base interaction.

 

A hálózatüzemeltetés tervezést segítő eseménykezelési megoldások

Techniques for Incident Management to Support Network Operations Planning
Szerző(k):
A. Karndacharuk, A. Hassan
Austroads Australia
Terjedelem: 52 oldal

This report investigates current local and international incident management techniques and proposes an Australasian incident management framework that supports network operations planning. A literature review highlights the fact that traffic incident management (TIM) is not only a process of managing multi-agency, multi-jurisdictional response to road traffic incidents, but also a broader management program that involves an objective setup, stakeholder collaboration, option development and selection, implementation and performance evaluation. Baseline and emerging TIM techniques and practices for the collection of road and traffic data and the response to incident management needs were also reviewed and new and emerging techniques for traffic incident management identified.
To assist in the establishment of a harmonised TIM methodology across Australasia, an incident management framework was developed based on the leading practices and techniques. The adoption of this integrated framework, which is underpinned by seven management principles, would improve the operation and safety of the road network by reducing the impact of planned and unplanned incidents. While the potential implications and benefits of the new technologies within the TIM framework have been briefly discussed in this report, quantifying the safety and efficiency impacts of different TIM techniques requires further investigation.

 

Szemcsés anyagok deformációs tulajdonságainak javított laboratóriumi jellemzése

Improved Laboratory Characterisation of the Deformation Properties of Granular Materials
Szerző(k):
D. Bodin
Austroads Australia
Terjedelem: 129 oldal

This report examines the capacity of the extra-large wheel-tracking laboratory test method to predict the in-service performance of granular materials. Rutting is a common distress mode of unbound granular bases under thin bituminous surfacings. Five granular bases were tested for rut-resistance under accelerated loading and the results compared to a number of laboratory characterisation tests. The laboratory tests included large-scale wheel tracking, repeat load triaxial and shear strength. It was concluded that the large-scale wheel-tracking test was the best available test to rank granular base rut-resistance. It is a useful performance-based test, which can lead to significant cost saving by optimising the use of otherwise non-traditional locally available aggregate resources.

 

A nemzetközi egyenetlenségi index különbsége vonal lézeres és hármas lézeres mérésnél különböző textúrák esetén

Line Laser and Triple Laser Quantification of the Difference in International Roughness Index between Textured and Non-Textured Strips
Szerző(k):
B. I. Izevbekhai, H. J. Ahn
Minnesota Department of Transportation, USA
Terjedelem: 41 oldal

Practitioners have often wondered whether, during ride measurement with inertial devices, the motion of the laser through pavement texture introduces non representative values of international roughness index (IRI), particularly in certain textures. In response to this problem, a special texture study created a non-textured strip by a recession of the middle 4 ft of a texturing broom dragged longitudinally behind the paver. The study measured IRI and other surface properties in adjacent textured and non-textured strips by using a lightweight profiler outfitted with a line laser and a triple laser arranged in tandem. IRI measurements were performed after sufficient concrete strength gain and repeated as soon as the joints were sawn. The same measurements were repeated after the joints were deployed. Results showed a significant difference between the IRI of a textured strip and that of a non-textured strip. Further analysis indicated that, although texture appears to affect IRI, this effect was amplified by the type of laser used, as the triple laser appeared to indicate higher IRIs in comparison with the RoLine laser. Although the RoLine is not a reference profiler for IRI values unaffected by texture, the prevalence of the RoLine and the triple laser in construction acceptance testing is sufficient reason to be concerned about the difference inherent in the obtained results. Chi-square and t-test statistical analysis showed that laser type induced comparable and even higher IRI anomalies than did the experimental drag texture. In addition, the texture-induced IRI anomaly can be minimized by measuring smoothness for acceptance at least 2 weeks after paving. There was no significant difference in pavement noise in terms of on board sound intensity (OBSI) between textured and non-textured strips. The friction numbers derived from the Dynamic Friction Tester indicated a correlation between the nontextured and textured strip friction numbers in each of the 6 sections. This indicated that the finishing process before texturing continued to influence the microtexture even after the broom drag. This finding is limited to the texture types investigated. Therefore, extrapolation of these results to other textures should be done with caution due to anomalous laser –induced IRI on certain textures.

 

Kétsávos körforgalmak biztonsági és mobilitási értékelése

Evaluation of Safety and Mobility of Two-Lane Roundabouts
Szerző(k):
G. Parikh, J. Hourdos
University of Minnesota, USA
Terjedelem: 87 oldal

When looking at measures of fatal and severe-injury crashes, roundabouts have demonstrated improved safety performance compared to traditional signalized intersections. Despite this, when it comes to less severe crashes, multilane roundabouts fail to provide a similar benefit. Previous research into this topic has identified behaviors that are associated with crashes in two-lane roundabouts, with yielding violations and turn violations generally being the largest contributors to crashes. This study sought to build on that work by expanding the data collection effort to include more sites and relate the frequency of individual behaviors to specific design features. Ultimately, four roundabouts were chosen for data collection and analysis, with two of them being full 2×2 roundabouts and the other two half-2×2. These locations were University Dr. S and 5th Ave. S in St. Cloud (half-2×2), 185th St. W and Kenwood Trail in Lakeville (full-2×2), and TH-22 and Adams St. (half-2×2) and TH-22 and Madison Ave. in Mankato (full-2×2). In the last two, changes in traffic control were implemented to reduce failure-to-yield crashes, and the study compared the driver behavior before and after the interventions. In general, the collective results show that the problems observed in the earlier site are present in all of the other sites with scale variations prompted by geometric and traffic control design elements. For example, in the St. Cloud roundabout, an increased rate of right-from-inner-lane turn violations were observed, which can be attributed to the sharper deflection angles present. Additionally, from the aforementioned roundabout as well as the one in Lakeville, it was concluded that turn violation rates are affected on the single or multilane geometry of the links approaching the roundabout. Single-lane roads result in fewer left-from-outer-lane violations. Overhead lane designation signs result in reduced turn violations similar to the earlier studies’ interventions in the approach lane markings. Unfortunately, apart from confirming the trend, no successful design or intervention was discovered regarding yield violations.

 

Az úttervezés alapvető céljai

Fundamental Objectives of Road Design
Szerző(k):
D. Milling, L. Louis, M. Luy
Austroads Australia
Terjedelem: 60 oldal

This report identifies improvements to guidance, education and practice to ensure the fundamental objectives of road design are achieved in new and existing road projects. The report provides a foundational road design definition and a series of road design principles that it recommends be incorporated into the Austroads Guide to Road Design. While the project concluded that the design guidance in Australia is technically sound, it recommended: better educating designers and practitioners on the importance of road design objectives and how to achieve them; improving design development and evaluation guidance to enable designers to apply robust engineering judgment, value engineering, Safe System principles, and assess whole-of-life costs; providing evaluation tools to encourage the development and evaluation of multiple design solutions; adapting existing design practices including requiring practitioners to demonstrate how design solutions achieve the objectives of road design.

 

Vasúti útátjárók javított megoldása nehéz járművek számára

Improved Railway Road Design for Heavy Vehicles
Szerző(k):
P. Aumann, D. Milling, M. Tziotis, T. Makwasha
Austroads Australia
Terjedelem: 86 oldal

The report identifies road design improvements to better cater for the safe passage of heavy vehicles through railway level crossings. Crashes involving heavy vehicles have been identified as a major safety issue in Australia and New Zealand with the volume of heavy vehicles expected to significantly increase over the next five to 10 years. An analysis of heavy vehicle crashes at railway level crossings across Australia and New Zealand found that many locations did not have warning signs installed to the standards at the time of the crash, sight distances for approaching vehicle drivers were obstructed by development on abutting properties or vegetation, and delineation was poorly maintained. Several opportunities for improvements were identified, principally to guidance on applying the sight lines and sight distances for a range of approaches, particularly on curved roads. Other improvements suggested include the addition of a short stacking warning sign and improving delineation by having all road approaches sealed to enable pavement markings, such as RAIL X and edge lines.

 

Nehéz járművek vízszintes feszültségei és a burkolat felület teljesítménye

Heavy Vehicle Horizontal Stresses and Pavement Surface Performance
Szerző(k):
U. Ai, K. Sharp, N. Trevorrow
Austroads Australia
Terjedelem: 104 oldal

This report presents the findings of Austroads Project AT1540 Understanding the impact on pavement surfaces from next generation freight vehicles and developing practical network prediction models and responses. The main purpose of the project was to gain an improved understanding of the failure mechanisms that are particular to the pavement surfacing layer – as distinct from the structural layer – that may be caused by changing configurations and loadings of freight vehicles. The project led to the development of the Surface Wear Tester (SWT), which was demonstrated as capable of applying sufficiently high levels of horizontal force to a surfacing (with emphasis on sprayed seal surfacings) to allow comparative testing to be undertaken for a range of binder types and operating conditions. Possible amendments to the current prescriptive performance based standard for horizontal load are discussed. Avenues for further work are presented.