Fleet Replacement Modeling
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This project focused on two interrelated areas in equipment replacement modeling for fleets. The first area was research-oriented and addressed a fundamental assumption in engineering economic replacement modeling that all assets providing a similar service are equally utilized. It is shown that if assets providing a similar service are not equally utilized, than overall operational costs of a fleet increases. The second area addressed the need of the Oregon Department of Transportation (ODOT) Fleet Services Section for a modern, user-friendly, well constructed and documented fleet condition model. The state-of-the-art in equipment replacement modeling and the research on effective prioritization measures computable from existing data is discussed. A new model is developed utilizing the highest value of (Age/Age standard)+(Usage/Use standard) as a measure to prioritize equipment. The model is described and it is shown through simulation that the prioritization measure utilized performs better than several other suggested measures. This project was conducted jointly with the ODOT Fleet Services Section and the ODOT Research Section.
Drainage Facility Management System
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This research project identified requirements for a drainage facility management system for the Oregon Department of Transportation. It also estimated the personnel resources needed to collect the inventory to populate such a system with data. A total of 213 data fields were identified and defined. A pilot data collection effort indicated that the time to gather and enter the information on one culvert was approximately 3 person-hours. Extrapolating the pilot project to the entire Oregon highway system indicates that there are between 23,000 and 25,000 culverts to be inventoried. Based in part on this research project, the drainage facility management system is under development and an inventory of all the culverts is underway.
Effectiveness of Cathodic Protection
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The report provides a summary of Oregon’s experience with cathodic protection of coastal reinforced concrete bridges.
Thermal-sprayed anodes, foil anodes with a conductive adhesive, and carbon painted anodes are effective in distributing current to the steel reinforcement in concrete bridges. A resistive layer develops at the anode-concrete interface with increasing electrochemical age, thereby increasing anode polarization. In impressed current cathodic protection (ICCP) systems this is reflected in a higher circuit resistance. In sacrificial anode cathodic protection (SACP) systems it results in lower current output. Periodic wetting of the anode by rain, fog, and dew is an important factor in reducing anode polarization.
Catalyzed thermal-sprayed titanium anodes under ICCP service develop no significant anode polarization with electrochemical age. They perform well in both low and high humidity environments, and exhibit stable long-term performance.
Humectants based on LiNO3 and LiBr promote more effective performance of new and aged anodes in CP systems than untreated anodes. In SACP tests, LiBr was more effective
than LiNO3. In accelerated ICCP, LiNO3 was more effective than LiBr.
In SACP service, zinc hydrogel anodes produce a stable protection current sufficient to protect reinforcing bar from corrosion. There was practically no effect of changing moisture conditions on current production and no evidence of aging effects in an Oregon DOT field trial.
Environmental Durability of Reinforced Concrete Deck Girders Strengthened for Shear w/Surface-Bonded
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This research investigated the durability of carbon fiber-reinforced polymer composites (CFRP) used for shear strengthening reinforced concrete deck girders. Large beams were used to avoid accounting for size effects in the data analysis. The effort included determining the role of freeze-thaw, moisture, and fatigue on structural performance and developing analytical design procedures that account for durability.
The results showed that moisture infiltration behind the CFRP, combined with freeze-thaw, was critical in reducing shear panel stiffness and shear capacity. Long-term moisture exposure alone produced only a minor decrease in shear capacity. Freeze-thaw, combined with fatigue, had little effect on shear capacity if water infiltration was minimized. Fatigue caused some debonding, but the debonding was not significant enough to affect capacity.
Use of ACI-318 with ACI 440 provided conservative predicted shear strengths after environmental exposure. However, the ACI approach did not provide uniform levels of safety because the observed conservatism was built into the prediction for the unstrengthened base specimens but not for the CFRP contribution. Consequently, a recommendation of the research is to apply the environmental exposure factor at the final design step to limit the effective CFRP stress/strain. For locations with very large numbers of wet freeze-thaw cycles and extended exposure to continuous moisture, the environmental reduction factors should be reduced even further. To better predict the CFRP bond strength demands that can occur due to shear-moment interaction, a further check of the design should be made beyond those required by ACI-440.
Development of a Decision Model for Selection of Appropriate Timely Delivery Techniques for Highway Projects
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This report describes Research Project SPR646 which explored the potential use and selection of various means for ensuring or increasing schedule performance of highway transportation projects at the Oregon Department of Transportation (ODOT).
Digital Image Rectification Tool for Metrification of Gusset Plate Connections to Steel Truss Bridges
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A method was developed to obtain dimensional data from photographs for analyzing steel truss gusset plate connections. The method relies on a software application to correct photographic distortion and to scale the photographs for analysis. The approach enables rapid and accurate collection of dimensional measurements compared to traditional methods. Users can quickly create AutoCAD drawings by collecting dimensional information about the gusset plates from the photographs. The rectified photographs provide a record of field conditions that can be compared with subsequent field inspection results to help identify and quantify long term changes in visual characteristics. The implementation procedure is straightforward and does not require specialized knowledge of photogrammetry. It can be practically employed under field conditions using current technology and personnel, and it reduces the likelihood of data entry errors. Dimensional measurements from the method provide results that are as good conventional field measurements and are within tolerances that most engineers would find reasonable for gusset plate connection capacity evaluations.
Animal-Vehicle Crash Mitigation Using Advanced Technology - Phase II: System Effectiveness and System Acceptance
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This project was initiated in the fall of 1999. The results through the fall of 2005 (Phase I) have been documented in detail in an earlier report. The accomplishments of Phase I included the following: the identification of existing animal detection system technologies and their vendors; the selection of two of these systems for field tests; the deployment of the two selected systems (one in Yellowstone National Park in Montana, and one in Pennsylvania); the documentation of the experiences with system installation; the testing of the reliability of the systems; and formulating advice for the future development and application, including cost-benefit analyses. One of the two experimental animal detection systems (Montana site) proved to be able to detect elk (Cervus elaphus) reliably. However, as a result of steep slopes and curves, the system had blind spots where large animals were able to approach the road undetected. Therefore the warning signs could not be attached, and the effectiveness of the system in reducing vehicle speed and in reducing the number of collisions with large wild animals could not be evaluated.
In Phase II of the project, subject of the current report, system modifications reduced the blind spots so that the warning signs could be attached. Speed measurements showed that passenger cars, pick-ups, vans, and trucks with two units or more all had lower vehicle speed with the warning signs activated compared to warning signs off. The number of collisions with large wild animals was 58-67% lower than expected, but because of the variability in the number of collisions and only one year of post installation collision data, the researchers could not test whether this reduction was significant. The opinions on and experiences of drivers with the system were documented in interviews. A majority would have liked to see the US Highway 191 system stay in place (59%), and thought animal detection systems were a good idea, in general (71%). In accordance with an agreement with Yellowstone National Park, the system was removed in fall 2008, due to high maintenance, lack of spare parts and concerns about landscape aesthetics,. Finally, this report includes a recommended step plan for agencies considering the installation of an animal detection system alongside a road and recommendations for future research and monitoring of the reliability and effectiveness of animal detection systems.
A Fitness-for-Purpose Evaluation of Fracture Critical Electro-Slag Welds
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A fitness-for-purpose evaluation was performed on the electro-slag flange welds of the West Fremont bridge approach superstructures, per the request of FHWA. This evaluation required gathering knowledge of the material properties, fabrication defects and service loads pertaining to the weldments in question. The serviceability of the weldments was assessed based on the fatigue and fracture performance. It was concluded that the welds have sufficient toughness and fatigue resistance to remain in service with no retrofitting.
Evaluation of the Oregon DMV Medically At-Risk Driver Program
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Oregon is one of six states with requirements for mandatory reporting of drivers with medical impairments. In 2003, the state’s mandatory reporting program, administered by Oregon Driver Motor Vehicles (DMV) Services, was revised to cover an extensive range of cognitive and functional impairments. This report examines the safety risk of persons treated in Oregon’s revised Medically At-Risk Driver program. The incidence of crashes and traffic offense convictions before and after license suspension is documented and compared to crash and conviction incidence of persons treated in the DMV’s voluntary medical reporting program. Comparisons are also made to a representative sample of the state’s driver population. Structured interviews of program stakeholders were also undertaken to identify issues related to the program’s performance. The safety analysis and interview findings provided a basis for recommendations made in the report.
Oregon's ACTs, Cross-Jurisdictional Collaboration, and Improved Transportation Planning
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The Oregon Transportation Commission (OTC) created Area Commissions on Transportation (ACTs) to improve coordination, help prioritize infrastructure investment, and provide input on statewide transportation issues. The structure of the ACTs is designed to provide a cross-section of input from the state, regional, local, private, and community sectors. A research project was initiated to: assess the role and experiences of ACTs, research comparative approaches in the state and nationally, and develop and assess options for improving coordination and increasing effectiveness. This study used interviews, an on-line survey, case studies from Oregon and comparative studies from three other states to assess ACTs and identify options. The findings reveal that ACTs have improved the state prioritization process and increased communication across the parties involved, but they face challenges in relation to cross-regional coordination, strategic investment decisions, and regional problems such as urban travelsheds. The study highlights a range of options for improving ACT functioning under its current structure, and more significant options that would require policy and structural changes.
Using Archived Data to Measure Operational Benefits of a System-Wide Adaptive Ramp Metering (SWARM)
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A System-Wide Adaptive Ramp Metering (SWARM) system has been implemented in the Portland, Oregon metropolitan area, replacing the previous pre-timed ramp-metering system that had been in operation since 1981. SWARM has been deployed on six major corridors and operates during the morning and afternoon peak hours. This report presents results of a “before” and “after” evaluation of the performance of two freeway corridors as part of ongoing efforts to measure the benefits of the new SWARM system, as compared to the pre-timed system. The study benefited from using the existing regional data, surveillance and communications infrastructure in addition to a regional data archive system. The evaluation revealed that the operation of the SWARM system, as currently configured in the Portland metropolitan region, produced mixed results when comparing the selected performance metrics to pre-timed operation. For the I-205 corridor, the results were generally positive. In the morning peak period, SWARM operation resulted in an 18.1% decrease in mainline delay and decreased variability in the delay. For the afternoon peak period, improvements were also found (a 7.9 % decrease in mainline delay) with the exception of moderately congested days which saw an 4.7% increase in mainline delay. On the OR-217, however, significant increases were found in overall average delay. In the morning peak period, delay increased 34.9% while in the afternoon period delay increased 55.0%. These conclusions, however, must be tempered because of lack of ramp demand data. If an assumption is made that ramp demand changes correspond with the measured freeway VMT changes, it is likely that ramp delay decreased under SWARM operation (i.e. more vehicles were allowed on the freeway which would equate to lower delay for vehicles on the ramps). Another important finding of this evaluation was that implementation of the SWARM algorithm resulted in significantly more data communication failures in the traffic management system. While this outcome is specific to the ODOT communication infrastructure and hardware, it was not anticipated. These communication failures have the potential to impact other traveler information programs that depend on the freeway surveillance data as well as the SWARM algorithm. Finally, one of the intentions of this research project was to encourage ongoing evaluation and continuous improvement of the ramp metering system and, in general, the overall freeway management system. It is clear from the analysis that meter activation times and rates are necessary to evaluate system performance. Incorporating additional logging capabilities into the SWARM system would make it easier to evaluate system operations on an on-going automated basis.
Dynamic Travel Time Estimation Using Regression Trees
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The report presents a methodology for travel time estimation by using regression trees. The dissemination of travel time information has become crucial for effective traffic management, especially under congested road conditions. In the absence of collected actual observations on travel time, the vehicle speed can be predicted by using regression trees, which in turn is used as a proxy to estimate the travel time. To maintain stable prediction ability in both free flow conditions and near-capacity flow conditions on freeways, the regression tree model developed for this study includes thirteen explanatory variables, categorized in four variable types: traffic flow, incident related, weather data, and time of day. A total of four characterization standards (outliers, weather, incidents, and weekday/weekend) are used to characterize the daily traffic data sets to determine the best regression tree model(s) to predict a day in certain characterization. The results show that not only do the regression tree models have accurate prediction ability of vehicle speed and promising ability to estimate travel time, but also the regression tree models built upon other characterizations are preferred to predict a certain characterization. The loop-detector data on PORTAL (Portland Oregon Regional Transportation Archive Listing) system, for the I5-I205 loop in Portland, Oregon, is used to demonstrate the applicability of regression trees in this report.
Evaluation of Bent Caps in Reinforced Concrete Deck Girder Bridges Part 1 & 2
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This report describes research conducted to enable evaluation of existing vintage bent cap beams in reinforced concrete deck girder bridges. The report is organized into two parts: 1) flexural anchorage capacity response and prediction of reduced development length due to beneficial column axial compression and 2) structural performance of bent cap systems and their analytical evaluation. Each of these parts including descriptions of the experimental specimens and results of analytical studies is described separately. The research results from both studies are combined and used in an example to demonstrate the rating of an actual 1950’s vintage RCDG bent cap beam for continuous and single trip permit loads.
Acoustic Emission Testing of In-Service Conventionally Reinforced Concrete Deck Girder Superstructures on Highway Bridges
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Three reports were produced from research sponsored by the Oregon Department of Transportation on acoustic emission (AE). The first describes the evaluation of AE techniques applied to two reinforced concrete (RC) bridge girders, which were loaded to mimic in-service conditions. The main goal was to get a thorough understanding of how AE methods can be used with RC and in what way these methods can assist in maintaining the state’s aging RC deck girder bridges. Recommended settings for data acquisition and processing were evaluated. In addition to the complex full-scale beam components, studies were performed on smaller test specimens that improved understanding of stress wave propagation through reinforced concrete and the response of acoustic emission sensors in detecting these waves. Some qualitative and quantitative assessment methodologies were described, and examples and limitations of the methods were presented. Source locations in three dimensions were performed, and strategies on how to best deploy sensors were evaluated using Monte Carlo Simulations.
Determining Effective Roadway Design Treatments for Transitioning from Rural to Urban Areas
This report reviews an Oregon research effort to identify ways to calm operating speeds as the vehicles transition into developed suburban/urban areas from rural roads. Drivers of vehicles approaching the urban environment have few visual cues to reduce their speeds until their vehicles are well into the more urban environment. This report specifically reviews a simulator study for rural-to-urban transitions. The study included two pilot studies and one full scale study. The scenarios evaluated were ones that either physically or perceptually narrow the road at these transition locations. The specific transition treatments included in the full scale simulation were:
Though all enhanced speed reductions were minimal, the scenarios with the most effective speed reduction results included the median treatments (particularly the medians in a series or the treatment combined with a gateway). The layered landscape treatment and the gateway with lane narrowing treatment did not result in statistically significant speed reductions. Back to Top
- Layered landscape
- Gateway with lane narrowing
- Median treatment only
- Median with gateway treatment
- Medians in series with no pedestrian crosswalks
- Medians in series with pedestrian crosswalks
Estimating Flow-Duration and Low-Flow Frequency Statistics for Unregulated Streams in Oregon
Flow statistical datasets, basin-characteristic datasets, and regression equations were developed to provide decision makers with surface-water information needed for activities such as water-quality regulation, water-rights adjudication, biological habitat assessment, infrastructure design, and water-supply planning and management. The flow statistics, which included annual and monthly period of record flow durations (5th, 10th, 25th, 50th, and 95th percent exceedances) and annual and monthly 7-day, 10-year (7Q10) and 7-day, 2-year (7Q2) low flows, were computed at 466 streamflow-gaging stations at sites with unregulated flow conditions throughout Oregon and adjacent areas of neighboring States. Regression equations, created from the flow statistics and basin characteristics of the stations, can be used to estimate flow statistics at ungaged stream sites in Oregon. The study area was divided into 10 regression modeling regions based on ecological, topographic, geologic, hydrologic, and climatic criteria. In total, 910 annual and monthly regression equations were created to predict the 7 flow statistics in the 10 regions. Equations to predict the five flow-duration exceedance percentages and the two low-flow frequency statistics were created with Ordinary Least Squares and Generalized Least Squares regression, respectively. The standard errors of estimate of the equations created to predict the 5th and 95th percent exceedances had medians of 42.4 and 64.4 percent, respectively. The standard errors of prediction of the equations created to predict the 7Q2 and 7Q10 low-flow statistics had medians of 51.7 and 61.2 percent, respectively. Standard errors for regression equations for sites in western Oregon were smaller than those in eastern Oregon partly because of a greater density of available streamflow-gaging stations in western Oregon than eastern Oregon. High-flow regression equations (such as the 5th and 10th percent exceedances) also generally were more accurate than the low-flow regression equations (such as the 95th percent exceedance and 7Q10 low-flow statistic).The regression equations predict unregulated flow conditions in Oregon. Flow estimates need to be adjusted if they are used at ungaged sites that are regulated by reservoirs or affected by water-supply and agricultural withdrawals if actual flow conditions are of interest. The regression equations are installed in the USGS StreamStats Web-based tool (http://water.usgs.gov/osw/streamstats/index.html, accessed July 16, 2008). StreamStats provides users with a set of annual and monthly flow-duration and low-flow frequency estimates for ungaged sites in Oregon in addition to the basin characteristics for the sites. Prediction intervals at the 90-percent confidence level also are automatically computed.
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Johnson Creek Landslide Research Project, Lincoln County, Oregon
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A five-year study indicates that the Johnson Creek landslide moves in response to intense rainfall that raises pore water pressure throughout the slide in the form of pulses of water pressure traveling from the headwall graben down the axis of the slide at rates of 1.4 to 2.5 m/hr. in the upper part and 3.5 m/hr. to virtually instantaneous in the middle part. Vertical arrays of piezometers measured infiltration at rates of only 50 mm/hr., so infiltration is too slow to affect saturated water pressure except in the headwall graben. The hydraulic gradient through the slide mass is small and groundwater flow appears to be nearly horizontal, roughly parallel to the slide plane. These observations and the rapidity of pressure
transmission are consistent with a high effective hydraulic conductivity throughout the slide mass. Westward slope of the piezometric surface is consistent with better drainage in the western part of the slide. Movement episodes proceed by en masse movement when threshold pore pressures are reached followed by faster and faster movement of the middle portion of the slide when pore water pressure there rises above ~9.4 to 10.8 m head above the slide plane. In January 2003, slide velocity increased by an order of magnitude when head above the slide plane at the middle observation site reached 11.4 m while the western site reached ~9 m, ~2 m above its maximum for the following four winter seasons. Antecedent rainfall correlating with this accelerated movement was mean precipitation of 0.84 m in the previous 60 days and 2.1 mm/hr. in the 62 hours immediately before the movement. Antecedent deformation correlating with the accelerated movement was extension of 1 cm in the lower part of the slide, possibly raising effective hydraulic conductivity there. This increased hydraulic conductivity may have caused a uniquely rapid pore pressure response in the lower part of the side and the unique 2-m increase in head. With respect to engineering solutions for slide mitigation, the reduction of water pressures at the headwall graben by dewatering (e.g., drains or pumps) should be effective given the inferred high hydraulic conductivity of
the slide and sensitivity to pressure change at the graben. Limit equilibrium stability analyses indicate that 3 m of erosion would destabilize the slide for most of the winter season. This finding suggests that buttressing the toe of the slide is an effective long-term remediation option.
Techniques for Assessing the Socio-Economic Effects of Vehicle Mileage Fees
The purpose of this study was to develop tools for assessing the distributional effects of alternative highway user fees for light vehicles in Oregon. The analysis focused on a change from the current gasoline tax to a VMT fee structure for collecting highway user fees. A static model and a regression model were developed and used to assess the impact of such a change on households by income and by location (rural/urban). A discrete-continuous choice model was explored for addressing the more complex issue of how the change in policy would affect vehicle choice decisions in the long run and the resultant distributional impacts.
Results confirmed the regressive nature of the gasoline tax and showed that a change to a revenue neutral VMT fee of 1.2 cents per mile would result in a very small increase in regressivity (less than one percent for the lowest income group) in contrast to the five percent increase in regressivity caused by the increase in the price of gasoline between 2001 and 2006. The impact of a change to a VMT fee on rural areas was found to be opposite to that suggested by conventional wisdom. On average a household in a rural location would pay less under the revenue neutral VMT fee than under the gasoline tax, whereas those in urban areas would pay slightly more. Findings from the static and OLS models suggested that a change to a VMT fee is not likely to create a significant disincentive to purchase more fuel efficient or hybrid vehicles. The discrete-continuous model offered an appealing approach from a theoretical point of view to further address this question; however, the authors were not able to refine it enough to produce robust results.
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Given that the impact on income groups was virtually identical in both the static and the more complex OLS regression models, it may be best for policymakers to use the simpler model, as it is easier to explain.