The goal of this research project is to evaluate the performance of the crumb rubber test sections compared with the conventional control section and depending on performance, develop Colorado-specific materials and construction specifications for ground tire modified asphalt pavements. Also, the research project aims to develop guidelines and best management practices for the construction of ground tire modified asphalt pavements. Transverse cracking began in the rubber modified sections after 22 months of service and longitudinal cracking began after 29 months. The control sections have no transverse cracking to date with longitudinal cracking beginning to appear after 56 months.
Pavement construction and maintenance problems due to the presence of sulfates in limestabilized subgrade soils have been widely reported in many transportation projects. In Colorado, problems associated with sulfate-induced distresses have been observed at the Denver International Airport and, more recently, at the U. S. Highway 287 Berthoud By-pass project. It would be desirable if CDOT engineers could count on alternative soil stabilization techniques that are not affected by the potential presence of sulfates.
Living snow fences (LSF) are designed plantings of trees and/or shrubs and native grasses along highways, roads and ditches that create a vegetative buffer that traps and controls blowing and drifting snow. These strategically placed fences have been shown to be cost effective in reducing highway maintenance associated with blowing and drifting snow conditions.
The study found that FAST systems have demonstrated the potential to reduce the number of crashes and reduce the cost of winter maintenance activities, if sited at appropriate locations (e.g., high-traffic-volume ice-prone ramps). However, improved installation techniques and involvement of maintenance crews during FAST installation are necessary to further increase the cost-effectiveness of a FAST system deployment. Extra effort will be made in sharing the information gained from this research study by focusing on CDOT personnel involved in planning, design, construction, operation and maintenance of FAST systems.
Chip seals are used extensively by CDOT for extending pavement life. Chip seals utilizing locally available and minimally processed aggregates should be a more economical pavement preservation treatment than chip seals constructed with higher quality, more expensive aggregates. Low traffic roadways may not demand such materials to perform acceptably. After four winters and three summers service both experimental chip seals are performing well. It appears that locally available, minimally processed aggregates can be successfully applied as chip seal aggregate on low volume roadways.
Crack sealing and filling on hot mix asphalt (HMA) pavements are cost-effective pavement preservation techniques that improve pavement performance and extend the life of existing pavements. If performed in a timely and effective manner, crack sealing can extend the life of HMA pavements. CDOT sponsored this study to update its procedures and guidelines for crack sealing and filling of HMA pavements. The draft Guidelines included in this report reflect CDOT experience, current state-of-the-practice, and the most recent research findings, and address where and when to perform crack sealing and filling, material selection, installation methods, construction inspection, and follow-up evaluation.
Due to budget challenges, Colorado is looking for alternative funding sources for the operation and maintenance of its interstate safety rest areas (SRAs). As CDOT continues to close rest areas due to tight budgets, it should look for alternatives to fund their operation and maintenance. These alternatives include small-scale strategies such selling tourism related items or lottery tickets, and a large-scale strategy that includes developing a commercialized rest area outside of the interstate right of way through a public-private partnership. In addition, CDOT could advocate for changes to federal law.
Asphalt overlays are one of the most common tools for rehabilitating existing asphalt and concrete pavements. However, the performance of new overlays is often jeopardized by the cracking distress in the existing pavement. This existing cracking propagates, or reflects, through the new overlay to the surface of the new overlay. The rate at which this reflection cracking propagates to the surface is a function of overlay thickness crack severity, traffic loading and subgrade or subbase support. Reducing the rate at which these reflection cracks propagate to the surface of the pavement is desirable in order to lengthen the time between rehabilitation projects or crack sealing operations.
This report develops a framework for organizing risk-based decisions about design, maintenance, and operation for the Colorado Department of Transportation (CDOT) applying to various types of facilities. It also provides illustrative examples for the use of the proposed framework. CDOT has an opportunity to be a national leader in assessing risks, vulnerabilities, consequences and outcomes through the implementation of a risk-based framework for facility design, operations and maintenance.
Colorado could pursue fees based on actual travel as an alternative to the fuel tax. Revenues from mileage-based user fees (MBUF) would not vary based on fleet fuel consumption and would instead return revenue in proportion to use of the roadway network. Too many operational and technological questions remain unanswered, and must be tested and evaluated before the state would be ready to commit to a statewide implementation of this strategy.
The reuse potential of tire chips as coarse aggregates in pavement concrete was examined in this research by investigating the effects of low- and high-volume tire chips on fresh and hardened concrete properties. One concrete control mixture was designed, which well exceeds CDOT Class P concrete requirements.
Thermal Mapping surveys were carried out on approximately 1000 miles of the Colorado Department of Transportations (CDOTs) roads. The purpose of these surveys was to identify road surface variations across the network to determine whether forecast Thermal Maps or the data from the surveys would be useful to decision-makers in the CDOT regions.
The objective of this project was to integrate the American Association of State Highway and Transportation Officials (AASHTO) Mechanistic-Empirical Pavement Design Guide, Interim Edition: A Manual of Practice and its accompanying software into the daily pavement design, evaluation, rehabilitation, management, and forensic analysis practices and operations of the Colorado Department of Transportation (CDOT).
The purpose of this study was to quantify the initial design life of a roadways pavement prior to rehabilitation and provide specific performance information through the analysis of pavement management data and historical experience. The analyzed data may be used to estimate the initial life of a pavement which can be incorporated into the LCCA within CDOTs M-E Pavement Design Guide. It will also provide guidance to CDOT and subcontractors in determining the cost-effectiveness of different pavement designs, construction and maintenance costs.
The objective of this study is to determine if the development of a standardized subset of bridge plans s feasible and cost effective. The past 30 years of successful Colorado Department of Transportation bridge design can be used as a starting point to create a standardized subset of bridge plans.
This report documents the results of a research project to support CDOT in the area of Safety Performance Function (SPF) development. The project involved collecting data and developing SPFs for ramp-freeway merge zones categorized as isolated, non-isolated and weave. For each of these three categories, data for the period 2007 to 2011 were collected at sites selected to ensure statewide geographical representation and coverage of the range of traffic volume and other variables in each category. Separate SPFs were developed for Total, fatal+injury (FI) and Property Damage Only (PDO) crashes.