Showing papers in "Better Roads in 2002"

The quest for long-life asphalt pavement

Abstract: Perpetual pavement is a long-life asphalt pavement consisting of a three-layer hot-mix asphalt pavement intended to provide a life span of 50 years or more. The asphalt industry sought to combat the existing notion that asphalt is short lived and designed perpetual pavement to compete with portland cement concrete. The design of perpetual pavement includes flexible bottom layers that prevent distress, confining it to surface course. The three asphalt layers include a durable fatigue-resistant base layer, a rut-resistant and durable intermediate layer, and a rut-resistant, impermeable, and wear-resistant surface layer. The first placement of perpetual pavement was along a 2.5 mile stretch of I-710 in Long Beach, California.

Highway safety barrier system will cut accident rates

Abstract: Attempting to prevent crossover collisions, a new safety barrier has been installed on a seven-mile length of State Highway 74 (Lake Hefner Parkway) near Oklahoma City, Oklahoma. The wire cable barrier system, known as the Brifen Safety fence, consists of 3,333 posts supporting 140,424 feet of cable at a total cost of $1.3 million. The four-strand safety fence is the first of its design to be implemented in the United States.

Tree sap helps hold roadside shoulders together

Abstract: Lignosulfonates, or lignins, are starting to replace traditional oils and brines as binders and stabilizers for road applications. They are the "glue" that holds trees together and are a byproduct of pulping and sold in 50% suspended solution. A new application in New York State is using them on shoulders. An experiment in Murray, NY, used aggregate mixed with lignins for a three-ft.-wide shoulder at a depth of 4 inches. Previous, untreated gravel shoulders needed almost yearly replenishment. The lignin mix is still performing well after two and a half years. They are also on the state's list of beneficial use items because lignins aren't toxic and cost less.

Good winter maintenance boosts road safety

Abstract: While plowing and salting to de-ice are still important in winter road maintenance, the reported use of anti-icing strategies is growing quickly. According to a survey sponsored by members of the Strategic Highway Research Program's Anti-Icing/RWIS Lead States Team, 86% of states responding to the survey planned to expand or start anti-icing. Between 1997 and 1999, the proportion of DOT vehicles equipped for anti-icing rose from one-in-10 to one-in-five. The number of lane miles treated jumped 50% in the same period. About 75% of the states responding to the survey used Road Weather Information Systems to help determine the need for anti-icing. All of the states were using embedded pavement sensors. Anti-icing was less popular in Canada, the survey indicated. Half of Canada's 10 provinces reported using anti- icing on a total of 2.3% of their lane miles. Meanwhile, researchers at Michigan Technological University's Institute of Snow Research are developing a new technology called Anti-Icing Smart Overlays. By gluing ground rock to the pavement with epoxy, engineers hope to create an overlay that soaks up de-icing chemicals so they won't need to be reapplied every time it snows. A likely first use is on highway bridges.

Deep rehab for distressed pavements

Abstract: Cold-in-place recycling (CIR) is useful for older roads with sound structure but pavement that is too deeply distressed, cracks two inches deep or more, for surface repairs such as hot-in-place recycling or overlays. Separate machines are used for each task in a "train," for milling; screening and crushing; and mixing. Most productive in open terrain and can be done rapidly, as much as two lane-miles in a day, and compact, from 1.25 to 1.5 lanes for equipment, reducing detour needs. The resulting pavement is more flexible, which makes it good for regions with extreme changes in temperature. Heavier rollers are required for the more viscous mix. New York's Fulton County and Ontario's County of Wellington are two experienced users reporting satisfactory results.

How to make street and road intersections safer

Abstract: About 44% of reported road accidents are intersection-related and account for 23% of road accident deaths. Intersection safety can be improved by better traffic control devices, geometric designs, identifying locations in need of improvement using crash statistics, larger signs, smoother flow with designs like roundabouts, intelligent controllers and detectors, and audible pedestrian warnings. Driver error contributes to 93% of intersection crashes. A before and after study at eight roundabout locations in Maryland show they cut the number and severity of crashes. Also included is a list of resources for intersection evaluations and upgrades from the Institute of Transportation Engineers (ITE) and the Association of American State Highway and Transportation Officials (AASHTO).

Sma : built for the long haul

Abstract: Stone matrix asphalt (SMA) is gaining favor as transportation agencies place higher value on durability and strength and are willing to pay a little more for major gains in those areas. European studies show that SMA mixes generally last 25% longer. Fiber stabilizers and polymer modifiers improve resistance to rutting. The success is due to stone- on-stone contact of the coarse aggregate. The fillers and additives cause costs to rise from 20-40%, but the durability is at least that much, and travelers aren't disrupted as often or for as long. Still, placement requires vigilance to achieve desired results. One way to standardize the mix is to use a material transfer device with re- mixing capability. Specific pavers that are best suited to this type of job are suggested.

How to solve cracking problems around manholes

Abstract: Frost heave cracks around manholes can be avoided with a technique developed by the National Research Council of Canada. It uses heat naturally generated from sanitary sewers. The heat is trapped in aggregate placed around the manhole in a structure called a bag. The tapered section at the top of the manhole has slots that make it a natural radiator that keeps soil around the manhole from freezing and thawing. The bag is about 1 yd. in diameter and costs $160 for materials and installation for a new manhole, more for retrofitting existing ones. Contained in the article is a cross-section of an installation.

Asphalt stability improved by using synthetic wax additives

Abstract: High traffic loadings are causing an increase in rutted stretches in asphalt pavement that can last miles. Using asphalt modifiers such as bitumens significantly increases pavement's resistance to rutting under all conditions. Bitumens, residues from distillation of crude oil, are not affected by how much wax they contain, research has found. But straight-run and air-blown bitumens may benefit from the addition of synthetic waxes produced by the Fischer-Tropsch process. In one test section using bitumens enhanced with synthetics in Hamburg, Germany, a road where ruts two to three inches deep appeared in two years experienced only shallow ruts (0.125 inches) after four years.

Agencies and contractors- working together

Abstract: As an alternative to the traditional low-bid method for choosing a contractor, state DOTs and transportation researchers are looking at ways that build in more cooperation and collaboration to speed the procurement and construction process and minimize delays and disputes over changes in designs and costs. Design-build is one method gaining in popularity. It uses a lump-sum bid and eliminates middlemen consultants between the agency and the contractor. It also joins the contractor to the designer. However, political and legal restraints to ensure against collusion and conflicts of interest need to be addressed in many cases. Other processes being tried out include A + B bidding, which rewards contractors for cutting down on projects' completion times; pre-qualification of contractors and consultants to speed acceptance of bids; and performance specification, which sets objectives and leaves their achievement to the contractor.

Frp improves bridge deck life : fiber-reinforced polymer shortened construction time and lengthened deck life in west virginia

Abstract: Fiber-reinforced polymer is becoming more attractive as an alternative way to extend the service life of structural bridge components, especially in colder climates where they are exposed to corrosive de- icing agents. They are also lighter and take less time to construct. Disadvantages include a low modulus of elasticity and higher installation costs. Many engineers and contractors are also not familiar with them. Describes the use of fiber-reinforced polymer in West Virginia. Designs included a deck panel with a dual-cavity beam with an adhesive bond to a mirrored unit. Describes technical decisions such as load tolerances, crown, girder spacing and connection techniques. In this example, the polymer bridge cost 2.4 times more to build than a nearby pre-stressed concrete box beam bridge, but it took less time and didn't require the curing time of the concrete structure. That would reduce user costs by the public, which are not calculated in the overall cost of building the structure.

Recycling as a life-extending maintenance tactic

Abstract: Hot-in-place recycling (HIR) is now an affordable shallow-depth maintenance method for use before asphalt shows distresses deeper than 2 in. Improvements in heating equipment and techniques, slower and more gradual heating, and more efficient capturing of emissions make it more attractive. The most cost-effective technique is remixing, at single or multiple stages. Repaving adds a hot-mix asphalt overlay with remixing. The Colorado Department of Transportation is among the biggest users of HIR. The Texas Department of Transportation uses it in metropolitan areas for its smoothness.

Building a better road for less money

Abstract: Full-depth reclamation (FDR) value engineering was used to rebuild a local road to carry traffic detoured from a nearby freeway. Starting with the base, a new stabilization layer made with lime kiln dust was built up to eight inches' depth and made the final road 21% stronger at about 90% of the cost of conventional methods. FDR techniques also allowed the job to be done in less time.

Sound approaches to roadside erosion control

Abstract: Erosion control is benefiting from some new technology, though a lot of it depends on basic road design. A New Zealand environmental group, Seafriends, discusses elements of successful erosion control on its Web site. Elements include whether a road cut is on a sun-facing side of a hill, whether it is located on the crest, and where and how deep ditches are. Check dams, as simple as a bag of cement or as complicated as a graded embankment, can also be effective. Culverts help, too, but only if they are spaced closely enough to carry the maximum amount of water. The article includes other design tips such as incorporating migration paths and being aware of the heat and wind effects of asphalt roads.

Managing municipal streets

Abstract: This article looks at the major issues facing city street managers. Focus is on funding, traffic congestion, partnering, and using new technologies. Various methods for increasing and maximizing municipal income are discussed. Some of these include making use of pavement management programs, technology transfer information from LTAP centers, switching to performance-guaranteed contracts, lobbying administrators for needed funds, establishing working relationships with pavement management coordinators, engineers, and contractors. In order to better deal with traffic congestion, the article offers suggestions such as the use of decision-making software to deal with budgetary issues, geographic information systems (GIS), facility condition information systems, facility equipment maintenance systems, and maintenance management systems for municipal operations. The concept of partnering with other agencies or cities to share costs is also suggested. The article concludes with a discussion of how safety management can be achieved in municipalities by using technologies such as traffic signal timing synchronization, high occupancy vehicle lanes, red light traffic cameras, and traffic calming devices.

Downed i-40 bridge opened in just 47 days

Abstract: This article describes the 24-hour work schedule and new technology used by the contractor who completed repairs of the knocked down I-40 bridge in Oklahoma in just 47 days. The original time estimate was 6 months, but the contract specified completion in 120 days because of user costs imposed by lengthy detours. Traffic had to be back on the bridge in 57 days. Recovery of the vehicles that plunged off the structure after it was hit by a barge was included in the contract for stabilizing the structure. Demolition and removal of the fallen span took just two weeks. The final reconstruction phase started before the removal was complete, as crews focused on the piers and supports. Early-strength concrete was used, and its hardening was monitored by new Versiflex elastomeric bearings. Steelflex modular expansion joints and strip seal expansion were also used.

30 years of research pays off

Abstract: Researchers from the United States Forest Service and Oregon State University have been working with geosynthetics, a material technique used in ancient construction that may improve the quality of transportation construction today The simplicity of reinforced soil technologies improves a project's longevity and earthquake tolerance at a lower cost through the combination of polymeric materials as tensile reinforcements Reinforced soil will improve the construction of retaining walls, improved foundations, rock fall barriers, bridge abutments, and more

The rubblization solution

Abstract: Rubblization is growing in popularity among states in need of rehabilitating their interstate highway pavements without creating the secondary problem of reflection cracking caused when underlying slabs or plates shift because of temperature changes or loads. They are reduced to smaller pieces, rubble, compacted and used to support an asphalt overlay. The article describes practices of Arkansas DOT, which is among the most active user of the technique. They use it instead of replacing pavement with concrete because asphalt takes less time and is ready sooner. Also, hauling costs and landfill costs are eliminated.

Zinc-mesh jacket system improves corrosion control

Abstract: A severely corroded bridge in Florida is given new life by encasing its pilings with a zinc jacket called a Lifejacket Cathodic Protection System. It is comprised of zinc mesh and a fiberglass form and is used for decay caused by chloride-induced corrosion. The jacket produces a galvanic cell that creates enough electrical current to prevent further corrosion of embedded steel. Cathodic protection is the only technique proven to stop corrosion in salt-contaminated materials. The galvanic approach is self-correcting and needs little maintenance versus the other method, impressed-current systems, which need continuous adjustments to respond to changing environmental conditions. Gives detailed explanation of the Florida installation, including photos and figures illustrating the mechanics of the system. The cost compares well with standard pile jacketing and grows more economical over time.

Software analyzes u.s. bridges and conditions

Abstract: New software offers a bridge information system to locate structures, find bridge information, and summarize data analysis. A majority of bridges in the United States are 25 to 50 years old, meaning state repair and replacement projects for bridges will increase dramatically over the next twenty years as many state bridges deteriorate. The information in the system, drawn from the National Bridge Inventory, contains bridge information for all states and may aid contractors or bridge designers working on bridge maintenance projects.