Nemzetközi szemle: Február
Hálózati szintű pályaszerkezet tesztelés forgalmi sebességgel mérő behajlásméréssel
Network Level Pavement Structural Testing with the Traffic Speed Deflectometer
Szerző(k): S.W. Katicha, S.S. Gerardo, W. Flintsch, B.K. Diefenderfer,
Virginia Tech Transportation Institute
Terjedelem: 44 oldal
This report describes research conducted to incorporate pavement structural condition information obtained from the Traffic Speed Deflectometer (TSD) into the Virginia Department of Transportation (VDOT) pavement management system decision making process for bituminous pavement sections. Testing was conducted on a 4,000-mile (1,500 interstate miles and 2,500 primary roads miles) subset of the VDOT network. The report showed that the pavement structural condition, as measured by the TSD, has an impact on the rate of deterioration of the pavement surface. In addition, for the set of collected data, the consistency between the TSD and Falling Weight Deflectometer (FWD) in identifying the same weak sections was found to be higher than the consistency between repeated sets of FWD measurements performed in the Bristol district. The consistency was defined as the percentage of structurally weak sections identified by both devices as a proportion of the number of weak sections. Also, the distribution of the effective structural number (SNeff) calculated from the TSD measurements on interstate roads was found to be similar to that obtained from the FWD measurements. The relatively good consistency between the TSD and FWD SNeff and the similarities between the SNeff distributions suggest that the structural information derived from the TSD can be successfully used as an alternative to similar data derived from the FWD for VDOT network level pavement management applications. The resilient modulus (MR) based on FWD testing is a metric currently used by VDOT to characterize the subgrade strength. A number of TSD-based indices have been proposed in the literature to replace the FWD-based MR. In this study, all indices investigated that could be used to replace the FWD-based MR were also found to be highly correlated to the overall TSD-based structural properties of the pavement and not very highly correlated to the FWD based MR. Thus, adding a TSD-based measure of the subgrade strength was not recommended at this time. Although the reasons for this lack of correlation between TSD-based and FWD-based subgrade strength measurements are not clear, they likely include unquantified differences in subgrade moisture conditions between measurements from the two devices and also possible limitations of the TSD technology in capturing very small deflections far away from the load application.
Látható fény kommunikációs keretrendszer intelligens közlekedési alkalmazásokhoz
A Visible Light Communications Framework for Intelligent Transportation Systems
Szerző(k): H. Kulhandjian
Mineta Transportation Institute USA
Terjedelem: 36 oldal
In this work, we developed a visible light communication (VLC) framework that can be used for Intelligent Transportation Systems (ITS). ITS has been motivated by the need for reducing traffic congestion and offering better user experience in navigation and location-specific services. Recently, VLC has drawn a great deal of attention in the research community, including the development of new applications for ITS. It would be of great use to enable the traffic lights to be able to talk to the vehicles in their proximity and convey important information about the traffic condition. In this project, we developed a framework that can potentially support infrastructure-to-vehicle (I2V) and vehicle-to-infrastructure (V2I) communication. (In our context the infrastructure refers to traffic lights using VLC.) Specifically, traffic lights will be used to not only to order traffic flow, but also to share some important information to the cars. The developed smart traffic light system can provide information about the traffic conditions several blocks down the road and, in case of accidents, this information would be useful for the driver to detour their original route to help reduce congestion and save time. In order to do that we have developed a transmitter circuitry that is composed of an embedded system and optical electronics. In addition, we have developed the receiver circuitry in which the photodiode along with other circuitry is used for detecting and decoding the VLC signal coming from the traffic lights. We have also developed and experimented in a laboratory with a novel optical code-division multiple-access (CDMA) scheme for overloaded optical CDMA transmission in which the optical codes are uniquely decodable. This new coding system could potentially provide higher data rate in the VLC protocol establishment.
A stopvonal hatékonyságának értékelése a biztonság növelésére stop szabályozású csomópontokban
Evaluation of the Effectiveness of Stop Lines in Increasing the Safety of Stop-Controlled Intersections
Szerző(k): M. Duhn, P. Dirks, A. Loutfi, J. Hourdos, G. Davis
University of Minnesota USA
Terjedelem: 200 oldal
Stop lines are ubiquitous, but do they really impact intersection safety? Prior to this project, no long-term studies on intersection safety with stop lines had been completed. This project was developed with two parallel research efforts: a safety study and an observational study. The safety study was developed to address stop lines’ effects over the long term and used crash data from five cities’ stop-controlled intersections to perform regression and see if stop lines actually influenced safety. The observational study was developed to determine if stop lines have an effect on driver behavior at intersections and to look at where drivers were stopping. Video was collected at 16 different intersections before and after a stop line was painted. The safety study and observational study showed that stop lines did not have a significant impact on driver behavior or intersection safety, but other factors like speed limits and sight distance did. Implications for practice include carefully examining sight distance at the intended stopping point to ensure drivers have adequate sight distance in both directions. If sight distance is not adequate, moving the intended stop location or reconsidering whether the intersection should have signage — stop or yield — or be uncontrolled could yield better driver compliance and safety.
Zord időjárás index
Severe Weather Index
Szerző(k): Laura Fay, Natalie Villwock-Witte, PhD, Karalyn Clouser, David Veneziano
Montana State University, Iowa State University USA
Terjedelem: 248 oldal
A severe weather index (SWI) was developed and tested using RWIS (Road Weather Information System) data from 2012 to 2020. The developed SWI model has an overall adjusted R2 = 0.67. The severity bounds are defined as low (0 to 1.2), moderate (1.2 to 8), and severe (greater than 8). The SWI model was tested quantitively and qualitatively using 2019-2020 winter weather data and input from maintenance managers. The SWI was found to perform well at identifying low and severe storms. Future work calibrating the SWI will help to better define lower and upper bounds of the moderate severity category. Key outcomes of this effort outside of the development of the SWI model include the identification of locations where blowing and drifting snow impacts the road network, the identification of future sites for RWIS stations, survey results describing RWIS use by MDOT SHA maintenance crews, and a detailed review of the RWIS network and data. In addition to the development of the SWI, extensive recommendations have been made that aim at improving the SWI and overall winter maintenance operations.
A közúti hidak állapota – a Kongresszus figyelmébe
Highway Bridge Conditions: Issues for Congress
Szerző(k): R.S. Kirk, W.J. Mallett
Congressional Research Service USA
Terjedelem: 19 oldal
Of the 617,000 public road bridges in the United States, about 46,000 (7.5%) were classified as in poor condition in 2019. These data, along with some highly publicized incidents involving highway bridges, have led to claims that the United States is experiencing a crisis with respect to bridge condition. Federal data do not substantiate this assertion. The number of bridges classified as poor has consistently fallen over the past decade, totaling about 15,000 fewer bridges in poor condition in 2019 than in 2009. Although improvements have been made in most states, there remain major differences in the share of bridges in poor condition. Congress may want to evaluate whether states are making sufficient progress in reducing the number of structurally deficient bridges and whether future laws should reestablish specific requirements for bridge spending.
Kompozit burkolat értékelése Virgínia államban – kísérleti szakasz az US 60 úton
Assessment of Composite Pavement in Virginia: A Trial Section on US 60
Szerző(k): M.S. Hossain, H. Nair, H.C. Ozyildirim, A.K. Moruza
Virginia Transportation Research Council
Terjedelem: 66 oldal
The Strategic Highway Research Program 2 (SHRP2) identified composite pavement as a “renewal solution” to support for implementation, and the Virginia Department of Transportation (VDOT) received funding to demonstrate its potential. In 2017, this funding was applied to support major rehabilitation of two westbound lanes of US 60 in Henrico County, Virginia, a project that essentially replaced 1.1 miles of deteriorated concrete pavement with a new composite system consisting of continuously reinforced concrete pavement (CRCP) overlaid with stone matrix asphalt (SMA). This new composite pavement was designed in accordance with the 1993 AASHTO Guide for Design of Pavement Structures and was constructed in accordance with VDOT specifications and standards existing at the time. During construction, material properties were characterized to enable mechanistic-empirical (ME) analysis, and AASHTOWare Pavement ME Design software was then used to analyze the pavement again using the “asphalt concrete overlay over CRCP” option as suggested in the SHRP2 research. Because of the low truck traffic count on US 60, the predicted distresses for a 30-year design life were found to be very low compared to an analysis that uses the Pavement ME Design software default criteria. Through-the-thickness temperature changes were also monitored and it was found that the asphalt overlay provides an insulating effect for the underlying concrete, hence reducing the curling and thermal stresses in the concrete pavement. SHRP2 researchers suggested that the thickness of the concrete portion of a composite pavement could usually be 1 to 3 in less than that of a plain (bare) concrete for comparable performance. Similar trends were observed for a higher truck traffic scenario in this study when a composite pavement (CRCP overlaid with SMA) was analyzed using the Pavement ME Design software. VDOT maintains more than 500 lane-miles of CRCP that has been overlaid with asphalt at an average age of 26 years. These pavements, now considered “composite” pavements, are still in service, often after multiple asphalt mill and replace operations, with some as old as 52 years. The average life of these overlays is 10 to 15 years, with the combination of CRCP and SMA often providing 16 to 23 years per cycle. The main distress mechanisms in a composite pavement are reflective cracking and rutting. The natural cracking and rut resistance of SMA therefore make it an ideal option for the asphalt component of a composite system. Such a design will protect the concrete base before any distresses have developed while also moderating thermal stresses (the insulating effect). The prospects for superior long-term service with low maintenance costs are excellent.
Burkolat repedések általános típusainak szabványos meghatározása
Standard Definitions for Common Types of Pavement Cracking
Szerző(k): K.C.P. Wang, J.Q. Li, G. Yang
Oklahoma State University
Terjedelem: 478 oldal
Pavements are a critical part of our nation’s transportation infrastructure. As reported by the American Society of Civil Engineers (ASCE), 21% of the nation’s highways had poor pavement condition in 2015; driving on roads in need of repair cost the United States (U.S.) motorists $120.5 billion in extra vehicle repairs and operating costs or $533 per driver (ASCE 2018). Therefore, road surface condition should be properly evaluated, along with accurate and timely defect detection. The objective of National Cooperative Highway Research Program (NCHRP) project 01-57A is to develop standard, discrete definitions for common cracking types for asphalt and concrete pavements. The new definitions will help pavement cracking survey providers and pavement engineers at SHAs conduct objective cracking measurements and encourage continuing technological innovations by researchers and vendors. The standard definitions shall be used to facilitate comparable measurement and interpretation of pavement cracking. The definitions shall be of sufficient details to serve as the basis to meet user and system requirements for developing automated cracking software, and for being compatible with both existing and emerging image based data collection technologies. The new definitions will be primarily tailored for network level surveys with the hope that successful implementations of the definitions will directly help the application of new technologies at the project level.
A megszakított forgalmi folyam elméletének javított útmutatója
Improved Guidance on Interrupted Traffic Flow Theory
Szerző(k): A. McGann
(letölthető ingyenes regisztrációval)
Terjedelem: 60 oldal
This report summarises activities undertaken to update guidance on interrupted traffic flow theory contained within the Austroads Guide to Traffic Management Part 2 and Part 3. The updates to the guidance will enable practitioners to improve their fundamental understanding of interrupted traffic flow theory and more effectively manage congestion on the road network. A literature review has been undertaken to identify new practices relating to interrupted traffic flow theory. Key areas identified for development in Part 2 and Part 3 include bottlenecks, travel time reliability, roundabout theory, analysis of signalised intersections, active transportation and demand management, multi-modal considerations and traffic flow impacts of heavy vehicles. Three case studies have been developed to demonstrate key theories and processes outlined in the guide. The case studies support the content provided within the guides and provide commentary to explain the decision making processes and interpretation of results.