| Abstract XII |
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| Johnson Creek |
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Johnson Creek Landslide Research Project, Lincoln County, Oregon
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.
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| Fee Impacts |
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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.
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.
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| Teen Licensing |
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Effectiveness of Oregon's Teen Licensing Program
Significant changes in Oregon’s teen licensing laws went into effect on March 1, 2000. The new laws expanded the provisional driving license program which had been in effect since October 1989 and established a graduated driver licensing (GDL) program for all drivers under age 18. The program is intended to reduce fatal and injury crashes among teen drivers and to promote safe driving.
Two studies were completed by research organizations that were designed to assess the impact of Oregon’s teen licensing laws. The National Highway Traffic Safety Administration (NHTSA) published a study, Evaluation of Oregon’s Graduated Driver Licensing Program, conducted by the Center for Applied Research, Inc. (CAR). The American Automobile Association financed a study, Reducing the Crash Risk for Young Drivers, which was conducted by the Traffic Research Injury Research Foundation (TIRF) to review not only Oregon’s graduated licensing program but also programs in Ontario and British Columbia, Canada. Analysis of driver records as well as surveys and focus group research were included in these studies.
The Oregon Department of Transportation (ODOT) has synthesized the results of these studies. This report provides background information, summarizes the key findings of the two reports and presents conclusions and recommendations based on the results. The results indicate that Oregon’s graduated driver license program has safety benefits and it should be continued.
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| MSE Retaining Walls |
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Evaluation of Corrosion of Metallic Reinforcements and Connections in MSE Retaining Walls
Mechanically Stabilized Earth (MSE) retaining walls have become the dominant retained wall system on ODOT projects. The permanent MSE walls constructed on ODOT projects, in recent years, use metallic reinforcements and facing connections buried directly in the backfill soil. Accelerated deterioration of these structural elements would have serious financial and safety impacts for the Department.
Classical MSE wall design incorporates an estimate of deterioration of reinforcement by corrosion. Monitoring of actual corrosion performance, however, is an important element of managing the current inventory of MSE walls. Monitoring could answer key questions that can provide for the best management of the existing walls, and provide feedback to the design process for future installations.
This report details a literature review of methods for estimating and measuring deterioration of structural reinforcing elements in both concrete and MSE walls. It also presents a selected history of metallic reinforcement design specification and utilization. A listing of the MSE walls that can be identified in the ODOT Bridge Data System is included.
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| Concrete Barrier |
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Concrete Barrier Distress in La Grande, Oregon
Several precast concrete barriers in eastern Oregon were noted to be deteriorating at an advanced rate. The ODOT Research Unit took several core samples from the barriers and conducted analyses. Petrographic evaluations determined that the strongest link between barrier deterioration and any one factor was the amount of entrained air. In general, older, poor-quality concrete, which was continually exposed to freeze-thaw events, exhibited advanced signs of distress.
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| Transportation and Environment |
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Transportation and the Environment: A Research Agenda for Oregon
In February 2006 Oregon State University hosted a workshop — Transportation and the Environment: Linking Researchers, Transportation Providers and Indust,y — attended by nearly 50 participants representing transportation providers, industry leaders, and academic researchers for the specific purpose of creating a transportation and the environment research agenda. The participants discussed needs and opportunities in the areas of ecology and natural systems, land-use, planning and performance measures, emerging technologies, and enviromnental and socioeconomic relationships, Key needs and opportunities were identified, and an attempt was made to categorize the needed research.
Among the needs and opportunities for transportation and the environment research, the following ideas rose to the top during the workshop:
• Developing integrated decision-support systems;
• Identifying, developing, and testing opportunities in green infrastructure (including the localization of industries, such as clustering transportation industries, construction material use, and use of recycled materials);
• Developing a process for systematically repairing or replacing culverts within watersheds or ecoregions; and
• Identifying opportunities to study the relationships between transportation and the environment within the context of the development of new cities and community developments in Central and Northern Oregon.
The authors recommend that the new Oregon University Transportation Center play a central role to continue and expand the momentum of this proposed research agenda, to help fulfill its potential, and to allow ii to be relined and matured as collaborative partnerships grow and needs and opportunities present themselves.
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| Geosynthetic Materials |
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Geosynthetic Materials in Reflective Crack Prevention
Reflective cracking due to shrinkage and brittleness in asphalt pavements can seriously degrade an asphalt overlay before it is near the end of its design life. Geosynthetics have been used to impede the reflection of existing transverse cracking to the new overlay. The geosynthetics are intended to minimize the tension transferred to the overlay from the existing pavement. The Oregon Department of Transportation (ODOT) installed a test section consisting of 98 transverse cracks treated with five different geosynthetic types, 22 transverse cracks treated with crack filling only and a control section of 20 untreated transverse cracks.
The test and control sections were monitored from 1999 to 2007. Each of the 140 test sites were revisited once each year to determine if the cracks had reflected, and if they had, measure their length and width. At the end of the study comparisons were made to determine if the geosynthetic materials were effective at controlling (by preventing or lessening the return of) reflective cracking.
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| Multi-Lane Roundabout |
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Adjustment of Driver Bahavior to an Urban Multi-Lane Roundabout
In the summer of 2006, the city of Springfield, Oregon installed the first urban multi-lane roundabout in the state. It was hypothesized that after installation, speed variability on approaches to the intersection would decrease from the values with the previous signalized intersection. It was also hypothesized that the initially observed high incidence of driving errors associated with specific areas of the roundabout would decrease over time. Before and after speed recordings of approach roads to the intersection revealed a significant increase in mean speed, but no consistent change in speed variability. Some design features caused initial confusion amongst drivers negotiating the roundabout, but the number of observed incidences of confused behavior declined over the first six months of operation at a rate that fit a classic logarithmic learning curve.
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| Driver Improvement Program |
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Evaluation of the Oregon DMV Driver Improvement Program
This report provides an evaluation of the Oregon Department of Transportation-Driver and Motor Vehicle (DMV) Services Driver Improvement Program (DIP), which was substantially changed in 2002. Prior to 2002, the DIP was organized around four progressive steps involving advisory letters, warning letters, probation, and suspension. The current program is organized around two steps: restriction and suspension. The timeline to the steps in the current program have also been shortened. To evaluate the current program, driver records of persons suspended between January and July of 2004 were examined in relation to a sample of Oregon’s driving population. The incidence of crashes and traffic offense convictions of DIP subjects in the 18-month period prior to suspension was compared to the incidence of these events among the driving population. A similar comparison was also made for the 18-month period following suspension. A substantial reduction in the relative incidence of crashes and convictions among DIP subjects following suspension was observed. This finding is subject to the effects of regression-to-the-mean. An approximation of regression-to-the-mean effects was made based on prior evaluations of Oregon’s DIP that employed a true experimental design. A regression analysis was also undertaken using driver record information from the period prior to suspension to estimate the likelihood of post-suspension crash and traffic offense conviction involvement. The estimated likelihood of post-suspension crash involvement was significantly affected by the frequency of pre-suspension crashes, but not by the frequency of pre-suspension convictions. Conversely, the estimated likelihood of post-suspension convictions was significantly affected by the frequency of pre-suspension convictions, but not by the frequency of pre-suspension crashes. Two changes in the DIP are suggested in the concluding section of the report. The first change involves re-instituting warning letters, given their demonstrated cost effectiveness in the driver improvement literature. The second change involves the assignment of greater weight to crashes in triggering license actions, based on the regression findings.
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| Incentive/Disincentive |
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Establishing Guidelines for Incentive/Disincentive Contracting at ODOT
This report describes the results of a research project which explored the use of Incentive / Disincentive (I/D) contracting at the Oregon Department of Transportation (ODOT). The research found that I/D contracting is a relatively rare practice within ODOT. When I/D contracting occurs, the special provisions and parameters (such as setting incentive amounts) are managed on a centralized basis by a small group of individuals. These individuals have used engineering judgment to develop these provisions and parameters in an environment of little historical data. Most of the knowledge of I/D contracting resides with these individuals, and there is little summarized written information that others could use to also develop similar provisions and parameters. Nationally, there is a wide mix in the use of I/D contracting amongst the various departments of transportation (DOTs). FHWA and NCHRP have published reports that compile these experiences and provide recommendations for I/D contracting. This work at the federal level is the basis for the development of an ODOT methodology for identifying project conditions that could lead to the use of I/D contracts. ODOT’s Office of Project Delivery uses Operational Notices to document and disseminate operational procedures. A draft I/D Operational Notice is included in this report as a potential tool for implementation of the findings. Significant in I/D contracting is the establishment of the amount of the incentive (and disincentive). Previously published articles recommend that the incentive be set more than the “lower boundary” of contractor’s cost of the acceleration (plus a reasonable profit), but less than the “upper boundary” of the cost of the delay to the public. This latter “upper boundary” value is usually established through the calculation of Road User Costs (RUCs), which calculation is commonly performed by DOTs, including ODOT. The research discovered, however, that there is a lack of working-level techniques to establish the “lower boundary” of the contractor’s cost of acceleration plus reasonable profit. This research proposes a method of economic analysis in determining the contractor’s costs for acceleration. A model is developed that establishes the “lower boundary” and “upper boundary” parameters based on evaluations of contractors’ costs and Road User Cost (RUC) cost techniques. These boundaries in turn provide a range within which incentive amounts would be effective. While the model is demonstrated in Microsoft Excel, the calculation methodology could be performed on a standard form, calculator or a different spread sheet program. The standardization of the process through defined methods and/or program templates provides a formal method and basis for determining effective values for incentives – leading to consistency and auditability.
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| LRFR Live Load |
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Calibration of LRFR Live Load Factors Using Weigh-In-Motion Data
The Load and Resistance Factor Rating (LRFR) code for load rating bridges is based on factors calibrated from structural load and resistance statistics to achieve a more uniform level of reliability for all bridges. The liveload factors in the LRFR code are based on load data thought to be representative of heavy truck traffic nationwide. However, the code allows for recalibrating liveload factors for a jurisdiction if weigh-in-motion data of sufficient quality and quantity are available. The Oregon Department of Transportation is implementing customized liveload factors based on the analysis described in this report. The relatively low liveload factors obtained in the Oregon calibration are a logical outcome of the regulatory and enforcement environment in Oregon.
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