Nemzetközi szemle: November

Aszfaltkeverékek hosszú távú öregítése a teljesítmény vizsgálatára és előrebecslésére

Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction

Szerzők:  Y.R. Kim, C. Castorena, M. Elwardany, F.Y. Rad, S. Underwood, A. Gundla, P. Gudipudi, M.J. Farrar, R.R. Glaser (North Carolina State University, Arizona State University, Western Research Ins titute USA)

Terjedelem: 127 oldal

Kivonat:

This report presents the experimental, analytical, and computational research conducted under NCHRP Project 09-54. This project’s goals were to develop a long-term aging procedure for asphalt mixtures appropriate to the fabrication of performance test specimens and develop an asphalt pavement aging model for mechanistic–empirical (ME) pavement design and analysis. Original component materials and field cores from in-service and test track pavements from eight states and the Province of Manitoba, Canada, were used in this study. These pavement projects yielded a total of 18 different asphalt mixtures, including warm-mix asphalt (WMA).

A közösségi közlekedés és a kerékpár megosztás

Public Transit and Bikesharing

Szerzők: Hernandez, R. Eldridge, K. Lukacs (Toole Design Group, LLC, USA)

Terjedelem: 106 oldal

Kivonat:

In the last five years, as biking has increased in popularity, bikesharing programs have become widespread in North America. Bikesharing is a service, in which bicycles are made available for individuals to use on a very short-term basis. Like transit, bikesharing offers a more energy efficient alternative to single occupancy automobiles. It can thus serve as a complementary mode, a first-mile and last-mile solution, and a stand-alone mobility option. An increasing number of transit agencies have developed cooperative arrangements with bikesharing programs to strengthen the relationship between the modes. The implementation and integration of bikesharing programs can sometimes present challenges to transit agencies. Some transit agencies view bikesharing as competition for potential transit customers while other agencies view it as an opportunity and a catalyst for transit use. This synthesis provides a better understanding of cooperative transit and bikesharing relationships and documents the experiences of transit systems with bikesharing as a mode. The synthesis identifies the current state of the practice, including challenges, lessons learned, and gaps in information. Thirty-two representatives from bikeshare and transit agencies from 20 cities responded to the electronic survey. Additional information is offered in a literature review, an analysis of survey results, and five in-depth case examples.

Túlméretes és túlsúlyos járművek útvonal-engedélyezésének legjobb gyakorlata

Best Practices in Permitting Oversize and Overweight Vehicles

Szerző: Schaefer, S. Todd (Leidos USA)

Terjedelem: 72 oldal

Kivonat:

This final report for the Best Practices in Permitting Oversize and Overweight Vehicles is the summary of a research study completed on State oversize – and overweight-permitting practices, including automated vehicle routing and escort driver certification and identifies the areas of best practices. This report is intended to fulfill a recommendation by the U.S. Government Accountability Office (GAO).

Ultra-vékony aszfaltrétegek tervezése és építése a felületi bevonatok alternatívájaként

Design and Construction of Ultra Thin Overlays as an Alternative to Seal Coats

Szerzők: Hajj, A. Filonzi, A. Bhasinm A. Dormohammadi, C. Zhu, V. Tandon (The University of Texas USA)

Terjedelem: 208 oldal

Kivonat:

Friction loss is one of the most critical issues faced by agencies responsible for preserving a pavement structure. There are various methods used for surface treatments including seal coats, slurry seals, and ultra thin asphalt concrete overlays. Ultra thin overlays have increased in popularity due to their lack of noise and improved ride quality, as well as their reduced overall cost owing to the reduced layer thickness. This study had three major objectives: determine the best mix type for use as an ultra thin overlay, evaluate the volumetric-based criterion that is currently used to determine the optimum binder content for mixes used in ultra thin overlays using performance tests relevant for surface mixes, and identify the properties of the tack coat that are required to construct such mixes in the field. The performance evaluation was conducted using laboratory techniques including the Hamburg Wheel Tracking Device and the Three Wheel Polishing Device. Out of the six potential gradations or aggregate structures that could be used as an ultra thin overlay, three were found to be suitable based on the performance tests. It was also observed that the optimum binder content, as defined by the volumetric criterion, was also generally the optimum based on performance tests conducted in the laboratory.

Önvezető járművek szimpózium 2017

Automated Vehicles Symposium 2017

Szerző: Transportation Research Board USA

Terjedelem: 251 oldal

Kivonat:

The 2017 Automated Vehicle Symposium (AVS) was held in San Francisco, California, on July 11–13, 2017. The development, testing, building, and deployment of autonomous vehicles (AVs) continues at a rapid pace. These technologies will have a major impact on transportation safety and mobility, as well as the environment and urban forms. The introduction of these technologies also has the potential to disrupt the transportation system. This report presents the proceedings from the 2017 AVS. The report follows the general symposium agenda. The presentations by speakers in the general sessions are summarized, including the highlights from the 25 breakout sessions. A list of the posters presented in two sessions is provided. The appendices provide a description of the key topics covered in the breakout sessions.

Burkolatviselkedés előrebecslési modellek fejlesztése megőrző jellegű beavatkozásokhoz

Development of Pavement Performance Prediction Models for Preservation Treatments

Szerzők: Ozer, M. Ziyadi, A. Faheem (University of Illinois USA)

Terjedelem: 65 oldal

Kivonat:

The implementation of a pavement preservation program was initiated in Fiscal Year (FY) 2005 at the Illinois Department of Transportation (IDOT) by appropriating funding for four specific pavement preservation treatments. The types of treatments included micro-surfacing, slurry seals, cape seal, and bituminous surface treatments (also known as chip seals). The scope and funding level for the state’s nine highway districts has expanded over the years. As a result, several years of performance data was collected from the projects constructed since the inception of the program. In this study, the performance of preservation treatments used by districts as part of the pavement preservation program were evaluated. After treatments were applied, pavement condition prediction models were developed for nine preservation treatments. Two methodologies were followed in developing the models. The first is solely based on the collected data when historical pavement condition data were sufficient. Due to the lack of data for many of the treatments, an alternative method was used to develop models. A multi-criteria decision-making method known as the analytic network process (ANP) was used to integrate expert opinion collected through questionnaires into the model development. The proposed model form is consistent with the existing condition rating survey CRS prediction models with a single slope, with the addition of project-specific factors to adjust the deterioration rate. The model variables included the existing pavement condition prior to the treatment, traffic, and truck percentage, along with the base deterioration rate. According to the modeling results, chip seals, slurry seals, and Half-SMART treatments were among the shortest-lived treatments, with an average service life of 3–4 years. For micro-surfacing treatments, single-pass and double-pass, could extend the service life to approximately 6 and 7 years, respectively. The average service life extension for cape seal treatment was more than 7 years, whereas cold in-place recycling treatment, with surface overlay and surface treatment, can extend pavement service life by approximately 8–10 years. It was also found that the performance of the ultra-thin bonded wearing course UTBWC treatment can be comparable to that of the micro-surfacing treatments, by extending the pavement service life by 6 years on average with a wider range of variability.

Burkolat állapotértékelés felmérési felülvizsgált modellek az összes hibatípushoz

Revised Condition Rating Survey Models to Reflect All Distresses

Szerzők: Ozer, M. Ziyadi, Y. Feng (University of Illinois USA)

Terjedelem: 114 oldal

Kivonat:

Pavement condition assessment plays a key role in infrastructure programming and planning processes. Similar to other state agencies, the Illinois Department of Transportation (IDOT) has been using a system to evaluate the condition of pavements since 1974. Since 1994–1995, IDOT has been using a system to project future pavement performance as well. The condition rating survey (CRS) value is the index between 1 (failed) and 9 (new), representing the overall condition of pavement. The purpose of this study was to update and revise the existing CRS calculation and prediction models using new data. To accomplish the goals of the study, the CRS data was received for the years 2000–2014. The data was initially processed and cleaned in preparation for modeling. CRS prediction models were prepared for Interstate and Non-Interstate pavement types. The two-slope model was used for all asphalt-surfaced pavements, whereas a new model was proposed for concrete-surfaced pavements. The proposed model for concrete-surfaced pavements is a nonlinear survival type designed to capture the distinct deterioration patterns of concrete pavements with little to no reduction in CRS—followed by a rapid and linear deterioration and a flatter region at the end, once the pavement is saturated with damage. The CRS calculation models were updated to incorporate new distresses. Based on the literature review and the analysis of distress composition, it was found that IDOT’s distress ratings are generally in agreement with the ASTM standard—with the exception of alligator cracking. A database containing recorded distresses, used by experts, was referenced to add missing distresses, such as alligator cracking, for each Interstate model.

A fenntartási beavatkozások hatékonysága a burkolatállapotokban

Effectiveness of Maintenance Activities on Pavement Conditions

(letöltés ingyenes regisztráció után)

Szerző: Martin, L. Choummanivong (Austroads Ltd. Australia)

Terjedelem: 44 oldal

Kivonat:

The aim of this project was to clarify the effectiveness of pavement maintenance (preservation) activities, in the form of periodic maintenance and rehabilitation, on pavement condition and distress (roughness, rutting and cracking) deterioration rates. This was addressed by estimating trends in pavement deterioration in three jurisdictions (New South Wales, Queensland and Victoria) from a time series of observational data (supplied by the jurisdictions) using mostly iPave condition and deflection data. In order to assess the effectiveness of the various pavement maintenance treatments, a comparison of these observational trends with historical and predicted rates of deterioration was made. Comparisons of functional condition parameters (roughness, rutting and cracking) against the mean maximum deflection found that their deterioration rates were significantly influenced by pavement strength. The effect of traffic and climate on deterioration was not as strong as pavement strength.

Kátyúk megelőzése és innovatív javítása

Pothole Prevention and Innovative Repair

Szerzők: Ghosh, M. Turos, M. Hartman, R. Milavitz, J.L. Le, M. Marasteanu (University of Minnesota USA)

Terjedelem: 129 oldal

Kivonat:

Pothole repairs continue to be a major maintenance problem for many highway agencies. There is a critical need for finding long-lasting, cost-effective materials and construction technologies for repairing potholes. This research effort investigates critical components associated with pothole formation and pothole repair and proposes solutions to reduce the occurrence of potholes and increase the durability of pothole repairs. The components include investigating and documenting pavement preservation activities, experimental work on traditional repair materials as well as innovative materials and technologies for pothole repairs, stress analysis of pothole repairs to identify whether certain geometric configurations are more beneficial than others, evaluating cost analyses to determine the effectiveness of various repair methods. A number of conclusions and recommendations were made. Potholes are mainly caused by the delayed response to timely fixing common pavement distresses. The state of Minnesota has a number of preservation strategies that are available and have been successfully used. Recommendations are made to improve these strategies using documents made available as part of new Every Day Counts, EDC-4, initiative. Currently, there are no required specifications for patching materials. Mechanical testing can be used to select patching materials based on the estimated durability of the pothole repair, such as short-, medium-, and long-term. A number of new materials and technologies are available for more durable solutions for winter pothole repairs, however, they require additional heat source and are more expensive.

A forgalom sebességével mérő behajlásmérő értékelése Louisiana államban az útpályaszerkezet vizsgálatához

Assessment of the Traffic Speed Deflectometer in Louisiana for Pavement Structural Evaluation

Szerzők: M.A. Elseifi, Z.U.A. Zihan (Louisiana State University USA)

Terjedelem: 120 oldal

Kivonat:

Many state agencies have recognized the importance of incorporating pavement structural conditions in the selection of maintenance and rehabilitation (M&R) strategies along with functional indices. The Traffic Speed Deflectometer (TSD) has emerged as a continuous pavement deflection-measuring device as it operates at traffic speed and reduces lane closure and user delays. The objective of this study was to assess the feasibility of using TSD measurements at the network-level for pavement conditions structural evaluation in Louisiana and in backcalculation analysis. To achieve the objectives of the study, TSD and FWD measurements were collected in District 05 of Louisiana and data were available from experimental programs conducted at the MnROAD research test facility and in Idaho. Based on the results of the analysis, it is concluded that the deflection reported by both FWD and TSD for the same locations are statistically different, which was expected given the differences in loading characteristics and load type between the two devices. It is also concluded that surface roughness has a notable effect on TSD field measured deflections. The present study successfully developed a model to predict in-service Structural Number (SN) based on TSD deflections at 0.01-mile interval of a road section. The model was successfully developed and validated with SN calculated based on TSD and FWD deflection data obtained from two contrasting data sets from

Louisiana and Idaho. Furthermore, the estimated percentage loss in structural capacity from the model was in good agreement with the percentage loss calculated from FWD. The importance of considering structural indices along with functional indices was demonstrated based on statistical analysis and extracted cores. Core samples showed that the sections that were predicted to be structurally deficient suffered from asphalt stripping and debonding problems. Yet, some of these sections were in very good functional conditions. A methodology was developed to incorporate TSD measurements in the backcalculation analysis and for predicting pavement layer moduli. The proposed Artificial Neural Network (ANN) model showed acceptable accuracy in predicting the corresponding FWD deflections

(TSD*) from TSD deflection measurements with a coefficient of determination of 0.90. In addition, the backcalculated moduli from FWD and TSD* deflection measurements were in good agreement. The ANN model was also validated by comparing the critical pavement responses, number of cycles for fatigue failure, and Structural Health Index (SHI) calculated from FWD and TSD* measurements.