Nemzetközi szemle: Október
Átereszek és a talaj-szerkezet kölcsönhatás. 50 év változásai és 20 éves előretekintés
Culverts and Soil – Structure Interaction. Fifty Years of Change and a Twenty-Year Projection
Szerző(k): T.J. McGrath, M.G. Katona, L. Janusz, J. Vaslestad, A. Miglio, J. Goddard, (Transportation Research Board USA)
Terjedelem: 57 oldal
Kivonat:
This E-Circular was developed from presentations made during the 93rd Annual Meeting of the Transportation Research Board, in a session titled “Fifty Years of Culverts and Soil–Structure Interaction: What Have We Learned and What Does the Future Hold?” sewer, sanitary sewer, and drainage pipe industry, is largely unchanged and unchanging. Yet the past 40 to 50 years have seen significant changes in the pipe industry in terms of materials used, structure sizes, shapes, and joint capabilities. Design methodologies have become far more sophisticated, primarily through the use of load resistance factor design (LRFD) and computer-aided design such as the finite element method (FEM). The structure of the industry itself has changed as well, with new companies coming into the marketplace, consolidation of companies, and spin-offs by larger companies of specific pipe producing units.
Kisforgalmú burkolt utak burkolatgazdálkodási rendszerét támogató és javító legjobb gyakorlat
Best Practices to Support and Improve Pavement Management Systems for Low-volume Paved Roads
Szerző(k): Hafez, K. Ksaibati, R. Atadero (Colorado State University USA)
Terjedelem: 205 oldal
Kivonat:
The Colorado Department of Transportation (CDOT) has been trying to identify the most effective methods for managing low-volume roads (LVRs). These roads are facing multiple challenges including: reductions in maintenance budgets, impact of industrial activities, and potentially not receiving the most cost effective treatments. Considerable savings can be secured by implementing an effective and informed management system for all LVRs engineering issues, including: planning, design, and maintenance. This report documents current national and local practices and investigates treatment policies that are in place on LVRs by summarizing the results of multiple surveys. Four online surveys were sent to the TRB low-volume roads committee, eight state DOTs, local governments in Colorado, and the material advisory committee in the CDOT. Seventy-one transportation agencies and individuals responded to the survey. The findings of this study provide CDOT and transportation agencies nationwide with comprehensive guidelines and state-of-the-practice information for managing LVRs. These guidelines include information about defining low-volume paved roads and types of PMS data recommended on these roads. It also gives insight about the effectiveness of some of treatment strategies applied to LVRs by different states at different management levels. The participants emphasized the need for some innovative maintenance activities for LVRs and integrating optimization techniques. A comprehensive literature review is introduced showing the most commonly applied treatments and new technologies for maintaining LVRs. This report is a useful reference to present key planning, design, and maintenance that are successfully meeting LVRs management needs. The results of this synthesis report are used to inform the second phase of the project studying CDOT maintenance strategies for low-volume roads.
Colorado állam kisforgalmú burkolt útjain elvégzett fenntartási beavatkozások átfogó értékelése
Szerző(k): Hafez, K. Ksaibati, R. Atadero (Colorado State University USA)
Terjedelem: 172 oldal
Kivonat:
The primary objective of this report is to document the effectiveness of low-cost treatments applied to low-volume roads (LVRs) in Colorado. By analyzing historical pavement performance data and treatment records, the effectiveness of each treatment type was determined. It was concluded that some surface maintenance strategies are effective long-term treatments for fatigue, longitudinal, and transverse cracking. However, the effectiveness of these treatments depends mainly on the initial condition index. An alternative maintenance strategy was proposed for CDOT considering a light rehabilitation technique with a surface treatment for poor roads. A long-term analysis of road maintenance and costs was conducted on a case study in Colorado. The results show the impact of both current and proposed maintenance strategies on the future of pavement condition. It was found that the proposed strategy would enhance the effectiveness of current policies followed by CDOT. This report also investigates the badly deteriorated LVRs in Colorado considering a specific characteristic of marginal pavement conditions. Different treatment strategies were evaluated to explore how reliable applying more pavement maintenance techniques is on these roads. The analysis of funding needs shows that marginal roads can be improved effectively within a maintenance capital improvement plan of five years from 2016 to 2020.
Visszanyert aszfalt darabok hatása az aszfalt kötőanyag teljesítményére
Impact of Recycled Asphalt Shingles (RAS) on Asphalt Binder Performance
Szerző(k): Roque, Y. Yan, G. Lopp (University of Florida, USA)
Terjedelem: 132 oldal
Kivonat:
This study evaluated the effect of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) on virgin binder true grade and fracture energy density (FED). A mortar approach, which avoids the need for binder extraction, was adopted to quantify the RAP/RAS effect on virgin binder true grades by using the grade change rate (GCR) parameter. The existing data analysis method was found to yield unreliable RAP/RAS GCR results, and an alternative method was developed to predict the properties of RAP/RAS blended binders for GCR determination. The enhanced mortar approach successfully captured the stiffening effect of RAP/RAS: (1) RAS had greater GCR at high and low temperatures than the RAP; (2) the stiffest RAP had greater GCR than the other two RAPs; and (3) tear-off (TO) shingles exhibited greater high temperature GCR and slightly lower temperature GCR than the manufacture waste shingles. Results also revealed that RAP GCR is independent of RAP binder replacement rate, but RAS GCR increases exponentially with increased RAS binder replacement rate. Use of soft virgin binders appeared to effectively compensate for the stiffening effect of RAP/RAS, in terms of Superpave binder true grades. The limit of RAS content was found to be approximately half of the allowable RAP content for a given virgin binder. However, whereas RAP binder increased the FED of virgin unmodified binders, the opposite trend was observed for RAS binder, especially for the TO shingles which caused significant reductions in virgin binder FED. This is an important finding because decreased binder FED indicates deteriorated binder fracture tolerance. In addition, great caution should be exercised when polymer-modified asphalt (PMA) binders are used in RAP/RAS mixtures because both RAP and RAS decreased the PMA binder FED, with the RAS effect being much more pronounced. A follow-up study is recommended to extend the research efforts to mixture evaluation since mixture performance is governed by factors other than binder performance, such as RAP/RAS gradation and mixture gradation.
A sebesség, a sebesség előírások és a biztonság közösségi értékelésének jobb megértése felé
Szerző(k): Douma, F. Alarcon (University of Minnesota, USA)
Terjedelem: 33 oldal
Kivonat:
Speed continues to be a leading factor contributing to traffic fatalities in the U.S., implicated in over 9,500 deaths in 2015. Despite this, in recent years, some states have moved toward more lenient speed enforcement regimes. A public choice problem may be to blame: voters may not be demanding effective speed enforcement regimes of their elected officials. To explore this dilemma, this project attempts to ascertain whether there is a relationship between state speed laws, roadway fatality rates, and public perceptions of speed. Better data are needed for definitive conclusions to be made regarding a possible relationship between these three bodies of knowledge. This report suggests that by improving data on the role of speed in crashes and public perceptions regarding speed, developing a standard measurement of speed law enforcement in each state, and adopting more consistent speed laws across states, a virtuous cycle can be initiated that helps dismantle the public choice problem, thus enabling the establishment of more effective speed enforcement regimes throughout the U.S.
Az Austroads hosszú távú burkolat megfigyelési program összefoglalása 2016-17
Austroads LTPP/LTPPM Study – Summary Report 2016–17
(ingyenes regisztráció szükséges)
Szerző(k): Martin, L. Choummanivong (Austroads, Australia)
Terjedelem: 36 oldal
Kivonat:
The report provides a summary of works undertaken during the period 2016–17 for the Austroads project AT1064 – Long-term pavement performance (LTPP). Austroads has funded the long-term pavement performance study since late 1994. The project monitors the structural and functional performance of in-service pavement test sites across Australia. The report also presents a summary of the LTPP/LTPPM current conditions and historical performance trends over the entire monitoring period and a brief summary of results of a survey on future directions of the project.
Önvezető közúti járművek és a városok és régiók
Road Vehicle Automation and Cities and Regions
Szerző(k): Hoadley (POLIS EU)
Terjedelem: 16 oldal
Kivonat:
Polis is concerned about the optimism bias conveyed by the media and literature about the introduction of AVs, especially automated cars which appear to be the focus. Expectations are being created that self-driving cars will be there tomorrow, will always operate perfectly and will solve congestion and eliminate accidents. While automated cars may bring some benefits, there is also the possibility that their widespread introduction in urban areas could lead to increased congestion, negative environmental impacts (unless all AVs are electric and/or powered by renewables) and negative health impacts, if walking and cycling are discouraged. Their introduction therefore needs to be carefully managed in the context of sustainable urban mobility objectives. In other words, even if they prove to be technically and commercially viable, it might be necessary to limit the use of AVs for policy reasons.
A csomóponti látótávolság biztonsági hatásainak értékelési útmutatója
Guidance for Evaluating the Safety Impacts of Intersection Sight Distance
Szerző(k): Eccles, S. Himes, K. Peach, F. Gross, R.J. Porter, T.J. Gates, C.M. Monsere (VHB, Michigan State University, Portland State University USA)
Terjedelem: 46 oldal
Kivonat:
Most multiple-vehicle crashes at three- and four-leg intersections with stop control on the minor road can be classified as either gap-acceptance crashes or traffic control device violations (e.g., stop sign violations), with gap-acceptance crashes generally occurring more frequently. Gap-acceptance crashes include several crossing-path crash types: right turn into path, left turn into path, left turn across path, and straight crossing path. Intersection sight distance (ISD) is a key design element at intersections. It contributes to the ability of drivers on the minor road to identify an appropriate gap for departing from the intersection and entering or crossing the major road. Designs that provide adequate ISD also allow drivers on the major-road approach to see stopped vehicles on the minor-road approach so that they can be more aware and prepare to slow or stop if needed.
A csomóponti látótávolság biztonsági hatásai
Safety Impacts of Intersection Sight Distance
Szerző(k): Eccles, S. Himes, K. Peach, F. Gross, R.J. Porter, T.J. Gates, C.M. Monsere (VHB, Michigan State University, Portland State University USA)
Terjedelem: 119 oldal
Kivonat:
This report documents the methodology and presents the results of a study aimed at estimating the safety effects of intersection sight distance (ISD) at stop-controlled intersections. To establish the relationship between ISD and safety at stop-controlled intersections, crash, traffic, and geometric data were collected for 832 intersection approaches with minor road stop control in North Carolina, Ohio, and Washington. These intersections represented a range of traffic volumes and major road cross section geometrics (e.g., two-lane, undivided; four-lane, undivided; four-lane, divided) in both urban and rural areas. Sites were selected for data collection without considering historic crash frequencies and severities. The data collection included field-measured ISD as a continuous variable using a standardized method as well as an exploratory measure of ISD quality. A cross-sectional study design with count regression modeling was used to quantify the relationship between safety and ISD. Target crashes were defined as those where a vehicle on the minor road collided with a vehicle on the major road. Target crash counts were associated with specific, measured values of an approach level ISD
(i.e., one observation of target crash frequency in the database represents the target crash frequency for one minor road and major road approach combination). The results suggest that the expected numbers of target crashes and target fatal and injury crashes are associated with available ISD. Target crash frequencies increase as available ISD decreases. ISD quality may also impact safety performance, but it was not included in ISD crash modification functions (CMFunctions) that were created as part of this research. Results also suggest that ISD is associated with the expected number of target crashes in a non-linear fashion. The sensitivity of the expected number of target crashes to changes in ISD is highest when ISD is shorter, and decreases as ISD increases (i.e., the safety benefit of increasing ISD from 300 to 600 feet is substantially larger than the safety benefit of increasing ISD from 1,000 to 1,300 feet). Moreover, the results suggest that the impact of ISD on target crashes and target fatal and injury crashes varies as a function of the major road two-way annual average daily traffic (AADT) and the major road speed limit. The sensitivity of the expected number of target crashes to changes in ISD increases as both major road traffic volume and speed limit increase.
Az automatizált gépvezérlés alkalmazása a közlekedési kivitelező iparban
Use of Automated Machine Guidance within the Transportation Industry
Szerző(k): White, C. Jahren, P. Vennapusa, C. Westort, A. Alhasan, Y. Turkan, F. Guo, J. Hannon, A. Dubree, T. Sulbaran (Iowa State University, The University of Southern Mississippi, University of Texas at Austin USA)
Terjedelem: 538 oldal
Kivonat:
Automated machine guidance (AMG) links sophisticated design software with construction equipment to direct the operations of construction machinery with a high level of precision, and improve the speed and accuracy of the construction process. AMG technology has the potential to improve the overall quality, safety, and efficiency of transportation project construction. This research project was undertaken to study AMG implementation barriers and develop strategies for effective implementation of AMG technology in construction operations. Early in the research effort, an expert contact group was established to obtain perspectives from agencies, contractors, designers, and equipment manufacturers. An AMG workshop was conducted to develop a list of capabilities that must exist and obstacles that must be overcome to facilitate seamless electronic data transfer—from the initial surveying, to the development of digital terrain models (DTMs), through design and construction, to final inspection and verification. The synthesis from the workshop helped provide a framework and content for completing the research. Summarized here are some of the key findings from this research project.