Transportation Intelligence

Volume 7 Number 1

February 2009

Safety

Administration

Concrete

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Safety
Vaccines for Roads: The new iRAP tools and their pilot application
It has been known for over half a century that low-cost engineering improvements to the safety of roads can save lives quickly and affordably. The methodology, however, has not been available to inspect existing roads systematically and then target programmes where they can save the most lives. Even new roads often fail to improve overall safety, particularly for p edestrians. This report from the International Road Assessment Programme (iRAP) describes the work done to invest in practical new tools for low and middle income countries and then pilot their application in four countries around the globe. (International Road Assessment Programme (iRAP) report, July 2008, 28 p.)

Climate Change
Anticipating the impact of climate change on road earthworks
Climate change and its consequences are one of the main preoccupations of the beginning of the 21st century. The first part of the report presents, as an example, regional scenarios of the climate evolution for Quebec and Switzerland. The second part focuses on water: lack or excess of water and its state. It deals with the cases of embankments, natural slopes, rise of sea level, modifications of the permafrost, and the increase of the wind force. Various examples are presented in the third part. They show, more particularly, failures of embankments and slope slides, due to the presence of a large quantity of water. If they are not the result of climate change, the frequency of such damages is likely to increase in the future. (PIARC Report 2008R12, 2008, 69 p.)

Safety

Two Low-Cost Safety Concepts for Two-Way Stop-Controlled, Rural Intersections on High-Speed Two-Lane, Two-Way Roadways
The Federal Highway Administration (FHWA) Office of Safety has identified intersections as one of its safety focus areas. As part of the FHWA efforts to reduce intersection crashes and the related injuries and fatalities, two concepts have been identified: (1) rumble strips on outside shoulders and in a painted yellow median island on major road approaches and (2) channelizing separator islands on side road approaches with supplemental STOP signs. Specifically, the strategies are low-cost countermeasures for intersections at two-lane, twoway roadways with two-way STOP-control (TWSC). The lane narrowing concept (concept 1) features the introduction of rumble strips on the outside shoulders and in a painted yellow median island on the major road approaches (figures 1 and 2).The objective of this first concept is to induce drivers on major roads to reduce approach speeds at intersections by effectively reducing the lane width. The minor road splitter island concept (concept 2) features channelizing separator islands on the side road approaches on which supplemental STOP signs are installed (figures 3 and 4). The objective of the second concept is to provide redundancy of the STOP sign and increase driver-compliance with the STOP sign. A third concept includes the combination of concepts 1 and 2 (figure 5). The concepts have greater potential for effectiveness on intersections of high-speed roadways. However, they can also be applied to intersections with lower posted speed limits. With the cooperation of several transportation agencies, these two strategies were deployed at a limited number of sites in the United States. This paper documents an evaluation of the operational and safety effectiveness of these strategies. (US Federal Highway Administration Summary Report FHWA-HRT-08-063, September 2008, 24 p.)

Best Practices for Low-Cost Safety Improvements on Iowa’s Local Roads
Many good maintenance practices are done routinely to ensure safe travel on low-volume local roads. In addition, there are many specific treatments that may go beyond the point of routine maintenance and in fact provide additional safety benefits with a relatively low price tag. The purpose of this publication is to try to assemble many of these treatments that are currently practiced in Iowa by local agencies into one, easy-to-reference handbook that not only provides some clarity to each treatment with photos and narrative, but also features references to agencies currently using that technique. Some strategies that are utilized by Iowa, other states, and are topics of research have also been included to allow the user more information about possible options. Even though some areas overlap, the strategies presented have been grouped together in the following areas: Signing and Delineation, Traffic “Calming,” Pavement Marking and RumbleStrips/Stripes, Roadside and Clear Zone, Guardrail and Barriers, Lighting, Pavements and Shoulders, Intersections, Railroad Crossings, Bridges and Culverts, and Miscellaneous. Our intention is to make this a “living” document, which will continue to be updated and expanded periodically as other existing practices are recognized or new practices come into being. (Iowa Center for Transportation Research and Education project 08-338, December 2008, 109 p.)

Warning Efficacy of Active Versus Passive Warnings for Unsignalized Intersection and Mid-Block Pedestrian Crosswalks
This study evaluated the efficacy of active versus passive warnings at uncontrolled pedestrian (ped) crosswalks (Xwalks), by comparing how these two warnings types influenced behavior of drivers approaching such Xwalks. Vehicle-Xwalk interactions were observed at 18 sites with passive, continuously flashing, or ped-activated warnings, yielding 7,305 no ped present and 596 ped present interactions. Vehicle velocities and accelerations were averaged for each interaction. Findings show no significant effect of warning type on overall velocities for either interaction type. With peds present only, for average velocities at successive 5m distances from the Xwalk, a downward trend in velocities from 25 to 5m is observed for passive and active warning sites, but not for pedactivated warning sites. Various lines of evidence point to a number of sources of ambiguity regarding the salience of uncontrolled Xwalk warnings, resulting in behavioral uncertainty by drivers interacting with such warnings. Mixed findings on effects of warning type in this study point to the need for further analysis of this problem area. (Minnesota Department of Transportation Report MN/RC 2009-03, January 2009, 141 p.)

Usability and Safety of Audio Tactile Profiled Road Markings
Audio Tactile Profiled (ATP) road markings (also known by road users as rumble strips) have been used at selected locations on New Zealand roads in recent years. However, a recent Land Transport Research report established that more extensive use of these markings over a wider range of traffic volumes and roadway situations would result in cost-effective crash reductions.
Based largely on consultation, the report provides an overview of practice and technology currently applied to the use of ATP road markings in New Zealand. It recommends best practice guidelines and changes to decision making processes, technical standards and some further research. The project provides information needed by highway managers and ATP road marking installation contractors. The recommendations inform the development of changes to rules and decision making procedures and, when adopted, should result in significantly increased usage of ATP road markings and a corresponding increase in crash savings. (New Zealand Transport Agency Research Report 365, February 2009, 70 p.)

Crashes in the Vicinity of Major Crossroads
Major crossroads are designed to facilitate the conflicting movements of numerous vehicles in a manner that is both safe and efficient. Accesses located within the functional areas of major crossroads add complication to intersection activity. In this research, the impact of accesses on crashes within major crossroad functional areas was analyzed. The statistical analyses show that the existence of accesses within the functional areas was correlated with increased crashes and crash severity costs. In particular, an increase in commercial access density was associated with increases in crash totals, crash rates, and rear-end crashes in intersection functional areas. The analyses also showed that study site intersections meeting Utah Department of Transportation (UDOT) corner clearance standards exhibited fewer right-angle crashes and lower crash severity costs. Finally, intersections that prohibited all unsignalized access had lower crash totals, crash rates, right-angle crash totals, and rear-end crash totals than intersections that allowed some unsignalized access. (Utah Department of Transportation Report UT-08.25, December 2008, 207 p.)

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Urban

Clear Zone - A Synthesis of Practice and an Evaluation of the Benefits of Meeting the 10 ft Clear Zone Goal on Urban Streets
This report presents research on the effects of the clear zone on urban curbed streets. The research was conducted in two phases. The first phase involved a synthesis of practice that included a literature review and a survey of practices in jurisdictions that have developmental and historical patterns similar to those of Iowa. The second phase involved investigating the benefits of a 10 ft clear zone, which included examining urban corridors in Iowa that meet or do not meet the 10 ft clear zone goal. The results of this study indicate that a consistent fixed object offset results in a reduction in the number of fixed object crashes, a 5 ft clear zone is most effective when the goal is to minimize the number of fixed object crashes, and a 3 ft clear zone is most effective when the goal is to minimize the cost of fixed object crashes. (Midwest Transportation Consortium Project 2006-05, Novemeber 2008, 158 p.)

Optimized thin layers – urban roads - the Kastrupvej experiment
This paper examines two new types of bridges, namely under-deck cable-stayed bridges and combined cable-stayed bridges, for prestressed concrete road bridges with single-spans of medium length. Both bridge types offer many advantages over conventional schemes in several aspects, such as structural efficiency, enhanced construction possibilities, and both economic and aesthetical considerations. They are very slender structural types with a very high structural efficiency, for which the materials used in the deck are reduced to one third of that in conventional bridges without stay cables. In this paper, the most important aspects of the structural behaviour of these bridge types are set out through the description of a careful selection from an extensive collection of bridges designed and analysed by the authors in a previous research project. In addition, a detailed set of design criteria for these bridge types is presented, based on the results of the extensive parametric study undertaken in the aforementioned research project. (Danish Road Institute Technical Note 66, February 2008, 78 p.)

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Administration

Asset Management Practice
Road Asset Management is a more developed approach to the task of steadily improving the satisfaction of road stakeholders. It enables road administrations to better optimise outcomes. It also incorporates the concept of business excellence in relation to both results and enablers. The objective of this report is to help road administrations with implementation of the Asset Management approach for management of road networks. (PIARC Report 2008R11, 2008, 163 p.)

Lessons Learned From International Experience in Congestion Pricing
France, Norway, Sweden, Germany, Switzerland, Singapore and Australia over the past three decades. Additionally, congestion pricing has been analyzed and evaluated through numerous studies in nearly all EU member countries, in Southeast Asia, Canada, Australia and New Zealand.
To further understanding of international pricing, “Lessons Learned from International Experience in Congestion Pricing” provides a summary of selected operational areawide congestion pricing projects outside of the U.S. The report draws lessons from a sample of projects with the richest and most relevant experience, focusing on three comprehensive area wide projects: Singapore, London and Stockholm. Each received in depth attention during planning, design, implementation and operational phases and have been monitored and evaluated carefully. These projects should be of particular interest now that several U.S. cities are beginning to examine similar area wide pricing strategies to address congestion, environmental, energy and funding problems in heavily congested downtown areas. (US Federal Highway Administration Report FHWA-HOP-08-047, August 2008, 85 p.)

Economic Competitiveness: Performance Measures for Transportation
The New York State Department of Transportation (NYSDOT) is developing a comprehensive set of measures that link investments in transport a tion to the general economic performance of the New York State Economy. The agency would like to understand in particular how NYSDOT investments singularly or in concert with investments by State and Local governments and Public Agencies/Authorities could improve economic competitiveness.
To establish the national and international best practices in terms of establishing the economic value of transportation network , the authors conducted two basic forms of research. Our first method was to review the existing literature concerning the relationship of transportation on economic development. Our second method was to conduct a survey of the State Departments of Transportation across the United States to request information on their use of economic performance metrics and reporting standards regarding the economic benefits of transportation investments. (University Transportation Research Center - New York, November 2008, 19 p.)

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Concrete

Revêtements drainants en pavés de béton (Permeable concrete roadway pavers)
The steady increase in the amount of paved surfaces has created a significant obstacle to the natural infiltration and drainage of precipitations and surface water. This causes ever greater volumes of runoff water to be channelled through stormwater sewer systems and watercourses. During heavy rainfall occurrences, these systems can become totally saturated, causing stormwater catchment facilities and local streams and rivers to overflow, and flooded roadways. The use of permeable concrete pavers provides a new solution to precipitation-related drainage issues.
The use of permeable concrete pavers for roadway surfaces provides on-site infiltration and filtration. The water is temporarily stored in the roadway foundation, and subsequently released into the soil. This alleviates pressure on sewer systems and assists in replenishing rapidly depleting water tables.
Permeable concrete pavers provide an effective drainage solution, in addition to responding to the public’s increasing commitment to environmental protection. (Dossier - Centre de recherches routières (Belge), Oct-Nov-Déc 2008, 20 p.)

Alternate Mitigation Materials for Alkali-Silica Reaction (ASR) in Concrete
Contractors are finding it difficult to obtain Class F fly ash for concrete paving projects, but CDOT specifications do not currently allow Class N fly ash to be substituted for Class F fly ash. The purpose of this study was to determine the effectiveness of Class N fly ash and other pozzolans for mitigating alkali-silica reaction (ASR) and resisting sulfate attack. First, a literature review was performed to find research on Class N fly ash. Second, other state departments of transportation (DOTs) were contacted to determine if Class N fly ash is used and how it is specified. Third, laboratory tests were conducted to determine the effectiveness of Class N fly ash and other materials in mitigating ASR when compared to Class F fly ash. Using one source of Class F fly ash, one source of Class N, and one source of reactive aggregate (fine and course), the effectiveness of Class N was determined by testing each combination in accordance to Colorado Procedures CP-L 4201 and CP-L 4202. Class N fly ash was found to be effective in mitigating ASR. Once the effectiveness of Class N and other products tested was determined, further testing on Class D mix design was performed for potential effects on fresh and hardened concrete. Testing included entrained air on plastic concrete, rapid chloride permeability (ASTM C1202-05), and compressive strength at 7, 28, and 56 days. (Colorado Department of Transportation Report CDOT-2008-10, November 2008, 74 p.)

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