TAC Transportation Intelligence

Pavements (voir aussi Chaussées)

Reclaimed Asphalt Pavement in Asphalt Mixtures: State of the Practice
Recycling asphalt pavement creates a cycle of reusing materials that optimizes the use of natural resources. Reclaimed asphalt pavement (RAP) is a useful alternative to virgin materials because it reduces the need to use virgin aggregate, which is a scarce commodity in some areas of the United States. It also reduces the amount of costly new asphalt binder required in the production of asphalt paving mixtures. This report informs practitioners about the state of the practice for RAP use in the United States as well as best practices for increasing the use of RAP in asphalt pavement mixtures while maintaining high-quality pavement infrastructures. Based on an evaluation of pavements containing 30 percent RAP through the Long-Term Pavement Performance (LTPP) program, it has been determined that the performance of pavements containing up to 30 percent RAP is similar to that of pavements constructed from virgin materials with no RAP. This report is of interest to engineers, contractors, and others involved in the specification and design of asphalt mixtures for flexible pavements, as well as those involved in promoting the optimal use of RAP. (US Federal Highway Administration report FHWA-HRT-11-021, April 2011, 60p.)

Performance Monitoring of Mechanistically-Designed Pavements - 2010 Data Collection
In order to verify its mechanistic pavement design procedures and review and update the life-cycle cost models used in the pavement selection process, the Illinois Department of Transportation (IDOT) conducted pavement performance monitoring. IDOT’s Bureau of Materials and Physical Research (BMPR) initially conducted performance monitoring on mechanistically-designed pavement contracts in the 1990s. In 2000, this effort was halted as BMPR experienced staffing shortages. BMPR resumed monitoring the performance of mechanistically-designed pavements in 2010. Pavement performance monitoring involves tracking distresses as they occur over time, and identifying the maintenance and rehabilitation activities that are performed on the contract. A total of 105 contracts were monitored: 55 full-depth hot-mix asphalt (HMA) pavements, 24 jointed plain concrete pavements (JPCP), and 26 continuously reinforced concrete pavements (CRCP). Contracts were broken into sections depending on the number of lanes on the project and the number of different cross-sectional elements (i.e. thickness, joint spacing, etc.). Distress data, weighted average rut depth, weighted average ride quality, and weighted average traffic values are provided for each section. Historical patching quantities are also presented. Also, graphs of patching quantities and overlays are presented as a function of age for full-depth HMA pavements, JPCP, and CRCP. (Illinois Department of Transportation Physical Research Report No. 159, March 2011,332p.)

Evaluation of Cone Penetration Testing (CPT) for Use with Transportation Projects
Cone Penetration Testing (CPT) has many advantages as a means for subsurface investigation. CPT consists of pushing a steel cone into the ground and recording the penetration resistance using sensors. Pore pressure, shear wave velocity and other measurements can also be taken using CPT. Several states have incorporated CPT into their subsurface investigation programs and the Ohio Department of Transportation (ODOT) has funded this project as a first step toward routine use of CPT in Ohio. Guidelines for CPT machine operation and data analysis are presented. CPT is expected to become a useful tool for ODOT subsurface exploration work and provide considerable cost savings over the long term. (Ohio Department of Transportation report FHWA/OH-2011/7, April 2011, 124p.)

Studded Tire Wear Resistance of PCC Pavements with Special Mix Designs
The performance of portland cement concrete mixes with higher flexural strength, higher cement content, and with Hard-Cem additive, carpet drag finish, and tined finish were evaluated over a period of five years to determine their resistance to studded tire wear. None of the pavements with special mixes or, mixes with Hard-Cem additive were more resistant to studded tire wear than conventional pavement with a 650 psi flexural strength mix design. The wear resistance of the pavement could not be correlated to either the method used to finish the concrete or the concrete’s flexural strength. Finally, the carpet drag finishing method produced a pavement with acceptable friction resistance. (Washington State Department of Transportation report WA-RD 658.2, February 2011, 70p.)

Use of a Double Chip Seal to Correct a Flushing Hot Mix Asphalt Pavement in Washington State
A chip seal constructed on an existing flushed roadway has the potential to result in bleeding or flushing of the new chip seal. The excess binder, if not properly accounted for during design and construction, will migrate to the surface of the chip seal and fill the aggregate void spaces leaving a flushed surface. The Washington State Department of Transportation (WSDOT) elected to construct a double chip seal to mitigate a flushing section of pavement on SR 20. This report documents the design and construction of the double chip seal and provides information on its initial performance. The double chip seal will be monitored for up to five years at which a final report will be prepared including conclusions as to its success or failure. (Washington State Department of Transportation report WA-RD 760.1, April 2011, 36p.)

Traffic Control (voir aussi Gestion de la circulation)

Integrating Active Traffic and Travel Demand Management: A Holistic Approach to Congestion Management
The purpose of this primer is to introduce and define the active traffic management (ATM) and TDM concepts and show the need for and benefits of integrating the concepts into efforts to address congestion on the most affected facilities. The primer provides a conceptual framework, originally suggested by the Dutch Ministry of Transport, for understanding the difference between traffic management and travel demand management. The primer underscores the need to integrate the two concepts into a holistic approach to congestion management. Considered alone, each concept presented in this primer is neither new nor innovative. What is new and innovative is the call to consider an integrated approach from the earliest planning stages of efforts to address congestion in a given region, system, or corridor. (US Federal Highway Administration’s Office of International Programs report FHWA-PL-11-011, January 2011, 24p.)

An Agency Guide on How to Establish Localized Congestion Mitigation Programs
This document provides guidance to state and local transportation personnel who wish to develop a formal program for mitigating congestion using localized and low-cost bottleneck treatments. It presents several templates for developing a localized congestion mitigation program, including documenting alternative templates in use by state Departments of Transportation and Metropolitan Planning Organizations.This guidance document is intended to aid agencies in establishing either ad-hoc or annualized programs that address localized congestion, much in the same way that an annualized safety-spot program would address localized safety issues. (US Federal Highway Administration Office of Operations report FHWA-HOP-11-009, March 2011, 63p.)

Evaluation of the Effectiveness of a Variable Advisory Speed Systems on Queue Mitigation in Work Zones
Variable Advisory Speed Systems (VASS) provide drivers with advanced warning regarding traffic speeds downstream to help them make better decisions. The purpose of this study was to evaluate the effectiveness of a VASS at mitigating queues in work zone entrances. It was anticipated that by implementing a VASS that queues would be reduced and vehicle flow increased in work zone areas. Three objectives of this study are: (1) research VASS systems that can be tested, (2) select and deploy a VASS in Utah at a long-term work zone, (3) perform a statistical analysis on traffic flow characteristic data to evaluate the effectiveness of the VASS that was deployed. To determine if the system was effective at reducing queue the speed data were analyzed to come to statistical conclusions. It was concluded that the VASS investigated was effective on weekends during evening peak hours when there was traffic slow down. There was no statistical difference on any day of the week when there was no slow down. It was recommended, however, that further studies be conducted to evaluate more about the system. (Utah Department of Transportation report UT-11.04, April 2011, 75p.)

Slow zones: their impact on mode choices and travel behaviour
We created the term 'slow zone' treatment or programme to generically describe the aim of any programme that modified the physical road environment in such a way it would moderate driver behaviour, slow vehicle traffic, and/or improve the environment of the neighbourhood. Within this definition, slow zone treatments included: traffic calming (local area traffic management), 30km/h zones and limits, home zones, mixed priority routes, neighbourhood accessibility planning, road capacity reduction, shared space and complete streets. We hypothesised that the often dramatic and clearly visible changes to streets created by establishing slow zones could also have substantial impacts on aspects of travel behaviour, in particular mode choice and travel patterns. We proposed to examine international experience in the development, implementation and monitoring of slow zones to identify what types (if any) of slow zone treatments contributed to changes in mode use and/or travel behaviour, other than reducing driving speed. We wanted to take the 'best practice' slow zone treatment(s) and compare them with slow zone treatments in New Zealand, with a view to providing a sound method to test their cause-and-effect on a broader range of impacts, particularly mode use and travel behaviour. That is, we proposed to lay the foundations for progressing the evaluation of slow zones in New Zealand by completing a comprehensive 'evaluability assessment'. (New Zealand Transport Agency report 438, March 2011, 110p.)

Life Cycle and Economic Efficiency Analysis Phase II: Durable Pavement Markings
This report details the Phase II analysis of the life cycle and economic efficiency of inlaid tape and thermoplastic. Waterborne paint was included as a non-durable for comparison purposes only. In order to find the most economical product for specific traffic and weather conditions, the project examined the relationship between the pavement marking materials’ retroreflectivity and input variables. For three to four years, retroreflectivity data was collected from six locations in the state of Maryland. The sites were selected based on the amount of traffic and snowfall they received. Phase I of this study was done with one year of data, but that data collection period could not provide reasonable and reliable estimates of future retroreflectivity. As hoped, a two-year extension of the data collection period produced better estimates. Although inlaid tape’s estimated life cycle was longer than thermoplastic’s, thermoplastic’s lower cost made it the more economical material for all conditions. (Maryland State Highway Administration report MD-11-SP808B4P, April 2011, 52p.)

Life Expectancy Evaluation and Development of a Replacement Schedule for LED Traffic Signals
This research details a field study of LED traffic signals in Missouri and develops a replacement schedule based on key findings. Rates of degradation were statistically analyzed using Analysis of Variance (ANOVA). Results of this research will provide a methodology for engineering managers in state departments of transportation and local communities in identifying best practices and replacement standards for LED traffic signal technology. (Missouri Department of Transportation report OR11.015, March 2011, 75p.)

Safety (voir aussi Sécurité)

Intersection Safety: A Manual for Local Rural Road Owners
More than 20 percent of all traffic fatalities in the United States occur at intersections and over 80 percent of intersection-related fatalities in rural areas occur at unsignalized intersections. This document provides information on effectively identifying intersection safety issues in local areas, choosing the countermeasures that address them, and evaluating the benefits of those treatments. It is geared toward local road managers and other practitioners with responsibility for operating and maintaining their roads. It offers information on the procedures and processes to improve the safety of local rural unsignalized intersections and to reduce the potential for future crashes. (US Federal Highway Administration report FHWA-SA-11-08, January 2011, 60p.)

Roadway Departure Safety: A Manual for Local Rural Road Owners
Rural areas face a number of highway safety challenges due to the nature of their facilities. Roadway departure crashes are frequently severe and account for the majority of fatalities in rural areas. This document provides information on effectively identifying roadway departure safety issues in local areas, choosing the countermeasures that address them, and evaluating the benefits of those treatments. It is geared toward local road managers and other practitioners with responsibility for operating and maintaining their roads. This document offers information on the procedures and processes to improve the safety of local rural roadways and to reduce the potential for future roadway departure crashes. (US Federal Highway Administration Report FHWA-SA-11-09, January 2011, 68p.)

Safety Evaluation of the Safety Edge Treatment
Between periods of maintenance, pavement-edge drop-offs can form along the edge of highways. When a driver runs off the roadway, such drop-offs can hinder reentry and may lead to driver overcorrection, loss of control, or overturning on the roadway or roadside. The safety edge is a treatment that is implemented in conjunction with pavement resurfacing and is intended to help minimize drop-off-related crashes. This report examines the safety effects, costs, and benefits of this low-cost treatment for two-lane and multilane rural highways. The safety research was conducted as an observational before-after evaluation of treated sites using the empirical Bayes method. The economic appraisal consisted of a benefit-cost analysis. (US Federal Highway Administration report FHWA-HRT-11-024, March 2011, 100p.)

Safety Impacts of Highway Shoulder Attributes in Illinois
The single greatest category of highway vehicle crashes is run-off-the-road incidents. Significant material differences and elevation changes in shoulder edges pose a potential safety hazard when a vehicle leaves the travel way. Shoulder paving is recognized as a positive countermeasure to reduce a shoulder drop-off hazard. This report documents an in-depth analysis of safety impacts of shoulder attributes using data on Illinois statemaintained highways for period 2000-2006. The findings are expected to help Illinois Department of Transportation (DOT) update current design manuals. (Illinois Center for Transportation report FHWA-ICT-11-078, April 2011, 198p.)

Performance Analysis of Centerline Rumble Strips in Washington State
With a goal of reducing collisions, WSDOT implemented policy for installing centerline rumble strips on undivided highways and invested in funding strategies for those installations in 2006. There have been some limited studies on the effectiveness of those installations, but a more complete study is appropriate. This study evaluates the effectiveness of centerline rumble strips under a variety of traffic and geometric conditions. The findings will result in better guidance on when to use rumble strips to address various collision types. (Washington State Department of Transportation report WA-RD 768.1, March 2011, 96p.)

Evaluation of Pedestrian and Bicycle Engineering Countermeasures: Rectangular Rapid-Flashing Beacons, HAWKs, Sharrows, Crosswalk Markings, and the Development of an Evaluation Methods Report
This report documents a Federal Highway Administration (FHWA) project to quantify the effectiveness of selected engineering countermeasures to improve safety and operations for pedestrians and bicyclists. Through a combination of literature review, review of traffic control device experimental requests, practitioner panels, and meetings with FHWA, the research team identified four countermeasures for evaluation as well as the need for a handbook for practitioners conducting evaluations of traffic control devices. This report provides a brief summary of the evaluations of these four countermeasures and references to the full technical reports for each. (US Federal Highway Administration report FHWA-HRT-11-039, April 2011, 70p.)

Structures (voir aussi Ouvrages d'art)

Durability monitoring for improved service life predictions of concrete bridge decks in corrosive environments
The development of an effective strategy for the inspection and monitoring of the nation’s critical bridges has become necessary due to aging, increased traffic loads, changing environmental conditions, and advanced deterioration. This article presents the development of a probabilistic mechanistic modeling approach supported by durability monitoring to obtain improved predictions of service life of concrete bridge decks exposed to chlorides. The application and benefits of this approach are illustrated on a case study of a reinforced concrete barrier wall of a highway bridge monitored over 10 years. It is demonstrated that service life predictions using probabilistic models calibrated with selected monitored field data can provide more reliable assessments of the probabilities of reinforcement corrosion and corrosion-induced damage compared to using deterministic models based on standard data from the literature. Such calibrated probabilistic models can help decision makers optimize intervention strategies as to how and when to repair or rehabilitate a given structure, thus improving its life cycle performance, extending its service life and reducing its life cycle cost. (National Research Council of Canada Institute for Research in Construction paper NRCC-52708, April 2011, 42p.)

Evaluation of Bridge Scour Research: Pier Scour Processes and Predictions
This report evaluates the current state of knowledge regarding bridge-pier scour, assesses leading methods for reliable design estimates of scour depth, proposes a structured methodology for scour-depth estimation for design purposes, and indicates pier-scour aspects in need of further research. It focuses particularly on research information obtained since 1990, showing that this information provides considerable new insights that compel the need to change the design method currently recommended by the principal authoritative design guides (notably FHWA’s HEC-18 and AASHTO) and used widely by bridge-engineering practitioners. Additionally, it indicates that several important aspects of pier scour processes remain inadequately understood and not yet incorporated into design methods. (TRB National Cooperative Highway Research Program (NCHRP) Web-Only Document 175, March 2011, 195p.)

Environment (voir aussi Environnement)

Assessment of Urban Form and Pedestrian and Transit Improvements as an Integrated GHG Reduction Strategy
This study is one of the first to test the effect of sidewalks on travel patterns and the first we know of to relate sidewalk availability with VMT and GHG emissions. Recently, several large jurisdictions in King County have developed local sidewalk data layers, creating a new opportunity to look at pedestrian infrastructure alongside other investment and policy strategies associated with reduced VMT and CO2. The study used travel outcome data from the 2006 Puget Sound Regional Council (PSRC) Household Activity Survey. The household-level analysis was restricted to households in King County where sidewalk data was already available, and modeled the association of urban form, pedestrian infrastructure,, transit service and travel costs on VMT and CO2, while controlling for household characteristics known to influence travel. The results provide early evidence in the potential effectiveness of sidewalks to reduce CO2 and VMT, in addition to mixed land use pattern, shorter transit travel and wait times, lower transit fares and higher parking costs. However, the lack of ability to collect sidewalk data from across all of King County limited the study results. (Washington State Department of Transportation report WA-RD 765.1, April 2011, 117p.)

Oregon Department of Transportation Greenroads Pilot Project: US 97: Lava Butte–S. Century Drive Section
This project is a Greenroads Pilot Project on the Oregon Department of Transportation (ODOT) project “US 97: Lava Butte–S. Century Drive Section.” Greenroads is a sustainability rating system for roadway design and construction (a complete description of Greenroads and its development can be found in TransNow report TNW 2009-13 and/or the Greenroads Manual available at www.greenroads.us). A Greenroads Pilot Project uses the Greenroads Rating System on an existing or planned project to determine (1) how the project scored as it is/was designed and constructed, (2) what the project could have scored had it pursued a Greenroads rating, (3) where best to revise the Greenroads Rating System to make it more usable for project personnel, and (4) determine how the Greenroads Rating System could best be used by the project and owner agency in pursuit of their sustainability goals. (University of Washington Transportation Northwest Regional Center report TNW2010-12, February 2011, 94p.)

Urban (voir aussi Zones urbaines)

NACTO Urban Bikeway Design Guide
The purpose of the NACTO Urban Bikeway Design Guide (part of the Cities for Cycling initiative) is to provide cities with state-of-the-practice solutions that can help create complete streets that are safe and enjoyable for bicyclists. The intent of the Guide is to offer substantive guidance for cities seeking to improve bicycle transportation in places where competing demands for the use of the right of way present unique challenges. It is important to note that many urban situations are complex; treatments must be tailored to the individual situation. Good engineering judgment based on deep knowledge of bicycle transportation should be a part of bikeway design. Decisions should be thoroughly documented. (US National Association of City Transportation Officials (NACTO) web site, April 2011, 304p.)

Urban Distribution Centers – A Means to Reducing Freight Vehicle Miles Traveled
The present study examines the model of freight consolidation platforms, and urban distribution centers (UDCs) in particular, as a means to solve the last mile problem of urban freight while reducing vehicle miles traveled and associated environmental impacts. This paper attempts to identify the key characteristics that make UDCs successful and discuss under what contextual settings (e.g., institutional, policy) they work best. After an extensive review of UDC cases already implemented in other countries, the study examined three UDCs cases with potential applicability to the New York metropolitan region, discussing models and relevant features and elements that may be transferred to the New York context. (New York State Department of Transportation report C-08-23, February 2011, 121p.)

The Urban Partnership Agreement: A Comparative Study of Technology and Collaboration in Transportation Policy Implementation
The problems faced by today's public managers are often too large to be solved by a single entity and require collaboration across government, nonprofit, and business sectors. As new technologies and systematic approaches transform the transportation field, cross-sector collaboration has become an increasingly important policy development and implementation approach. Particularly within the transportation field, an assemblage of technologies is often critical to implementing system-wide strategies aimed at, for example, mitigating traffic congestion. In many cases, designers and implementers of effective transportation policies must combine a variety of technologies with deft relationship building and management. Through the development of comparative case studies of three of the Urban Partnership Agreement initiatives, this research study will examine how technology and collaborative processes may be combined to achieve important transportation goals and create public value more generally. (University of Minnesota. Humphrey School of Public Affairs report, April 2011, 74p.)

Transportation Intelligence

Volume 9 Number 4

Français

August 2011

Planning

Pavements

Traffic Control

Safety

Structures

Environment

Urban

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2011 Canadian Surface Transportation Research Survey

Planning (voir aussi Planification)