Research Report Abstracts
Evaluation of the Safety Edge(SM) Application in Oregon
Back to Top
|This report summarizes a recent assessment of the Safety Edge SM that was performed to determine the feasibility of using this pavement edge treatment on Oregon construction projects. The report includes a review of research that has been published about the performance of the Safety Edge SM . The report also incorporates a state of practice review of the states currently using or considering the use of this treatment. Specifications, standard drawings, or technical documents developed by other agencies are included in the report appendix. |
ODOT performed one demonstration project and assessed the ease of use, time to train, and issues related to deploying the Safety Edge SM treatment in Oregon. It was found that the initial mounting of the shoe on the paving equipment was straightforward and could be done with limited training required. The site selected was free of guardrail and driveways, so the researchers could not assess functionality of the shoe at locations with obstructions.
As a result of this research effort, the research team developed draft language for a sample Oregon specification for the Safety Edge SM as well as a Technical Bulletin that addresses key issues related to benefits, cost, deployment, and similar for the Safety Edge SM. Though the Safety Edge SM will likely benefit most pavement projects, it should particularly be considered if the following conditions are present:
- A history of run-off-the-road crashes;
- Numerous sharp horizontal curves subjected to off-road tracking;
- Locations subject to roadside erosion; or
- Locations where vehicles can be expected to frequently exit and re-enter the active lane (i.e. rural mailbox clusters).
It should be acknowledged that the guidance included in the Technical Bulletin as well as the details given in the draft specification are based on the findings of the current research effort. As projects begin to incorporate use of the Safety Edge SM and ODOT staff and contractors become more familiar with the application process, it is expected that the specific guidance may be modified
Self Curing Admixture Performance Report
Back to Top
|The Oregon Department of Transportation (ODOT) has experienced early age cracking of newly placed high performance |
concrete (HPC) bridge decks. The silica fume contained in the HPC requires immediate and proper curing application after
placement to avoid early age cracks. Many construction contractors do not consistently apply adequate curing procedures,
and project sites may not have easy access to water. This problem led ODOT to investigate a self-curing admixture (SCA)
for bridge deck concrete mixes. The SCA reduces wet curing requirements by counteracting to some degree water loss due
to evaporation. An admixture in place of wet curing that allows HPC bridge deck concrete to cure properly without early
age cracking and without decreasing other performance requirements would provide another option for contractors. The
study showed that concrete with the SCA after a 3-day wet cure can produce similar results to standard HPC concrete with a
14-day wet cure. However, the concrete additives in the concrete must be compatible with the SCA
Evaluation of Alternative Pedestrian Control Devices
Back to Top
|A literature review, field study of Rectangular Rapid Flashing Beacon (RRFB) installations in Oregon, and a static survey |
on the sequencing of the Pedestrian Hybrid Beacon (PHB) were completed.
The field study conducted in this project was designed to compare side and overhead-mounted beacons and RRFBs. The
field study results indicated that the environment surrounding the crossing has an impact on compliance and that the
presence of a median can increase compliance.
The PHB study verified that drivers are confused about what these devices are and how they operate. For the first
deployment of a PHB in an area, a public education program is recommended during the early deployment of the PHB.
The Guidelines that have been developed as part of this project were based on the literature review and the Oregon field
study. The major recommendation is that RRFBs be installed on medians when side-mounted devices are considered and
at locations with posted speeds of 40 mph or less unless additional features such as stripping, signing , and advance
warning RRFBs are used. To reinforce the guidelines, a decision matrix was developed.
Should Oregon DMV Require a Knowledge Test at Renewal?
Back to Top
|Persons renewing their Oregon driver license do not need to take a knowledge test. Oregon DMV requested that ODOT Research Section review the testing practices of other states to determine what alternative approaches are taken to retesting adult drivers for their knowledge of driving practices and laws. A review of state driving laws and policies was completed. No state requires all driver license renewal applicants to take a knowledge test. Fourteen states require a knowledge test or traffic sign recognition test when renewing the driver license if the driver meets certain criteria. States with requirements primarily use criteria that relates to the driving record and license status. Typically it is suspended and/or revoked drivers that must take the knowledge test. In some cases the age of the driver is a consideration. |
It was also found that few states provide information on new traffic laws and safe driving tips that will be clearly visible to the driver accessing information on the website about driver license renewal.
Calibrating The Future Highway Safety Manual Predictive Methods For Oregon State Highways
Back to Top
The Highway Safety Manual
(HSM) was published by the American Association of State Highway and Transportation Officials (AASHTO) in the spring of 2010. Volume 2 (Part C) of the HSM includes safety predictive methods which can be used to quantitatively estimate the safety of a transportation facility. The resulting information can then be used to provide guidelines to identify opportunities to improve transportation safety. The safety performance functions (SPFs) included with this content, however, were developed for several states other than Oregon. Because there are differences in crash reporting procedures, driver population, animal populations, and weather conditions (to name a few), the State of Oregon needs to use calibrated SPFs when applying the HSM procedures to local Oregon facilities. Currently, the predictive methods have been developed for three facility types: rural two-lane two-way roads, rural multilane roads, and urban and suburban arterial roads. In this project, the research team calibrated SPFs for all three facility types based on their historic safety performance in Oregon. The report illustrates methods of site selection, the collection of crash and site-specific data, and analysis methods for calibration. Also, the report includes an evaluation of the crash severity distribution methods. With this information, Oregon agencies can use the calibrated HSM predictive methods to assess expected facility safety performance for Oregon conditions and facility alternatives.
Accelerated Bridge Construction (ABC) Decision Making and Economic Modeling Tool
Back to Top
|In this FHWA-sponsored pool funded study, a set of decision making tools, based on the Analytic Hierarchy Process (AHP) was developed. This tool set is prepared for transportation specialists and decision-makers to determine if ABC is more effective than traditional construction for a given bridge replacement or rehabilitation project. The tool set is user-friendly, flexible to accommodate a range of construction situations, transparent as to the method of calculation, and customizable to maintain future relevance. To accommodate this task, a comprehensive literature review on a number of relevant domains such as ABC construction techniques and decision making approaches, were completed. The findings were summarized into a decision model hierarchy that was also incorporated into the decision making software. The software was tested through evaluating a set of real-world construction projects. |
Pre and Post RRFB Installation
Assessment of Driver Yielding Rates Pre- and Post-RRFB Installation, Bend, Oregon
Back to Top
|The Oregon Department of Transportation improved two crosswalks on US 97 (Bend Parkway) near Bend, Oregon by installing Rectangular Rapid Flashing Beacons (RRFB), replacing signs, and enhancing pavement markings. At the location of the intersections where the RRFBs were installed the highway is a four-lane facility with a center median, bike lanes, and sidewalks. The posted speed is 45 miles per hour. At about the same time that the improvements were made at the two crosswalks on the Bend Parkway, RRFBs were installed at another nearby location in the City of Bend. As the use of RRFBs is considered experimental, particularly at locations with posted speeds in excess of 35 mph , an evaluation of driver compliance rates and conflicts at the three intersections was undertaken. |
Driver yielding rates increased significantly at all three intersections where RRFBs were installed. Prior to the installation of RRFBs, data was collected on a total of 159 crossings at the three intersections; following RRFB installation data was collected on a total of 211 crossings. The average yielding rate was 17.8%; following installation the average yielding rate more than tripled to 79.9%.
The conclusion of the study was that RRFBs should be considered for installation on high-speed facilities where there are posted speeds greater than 35 miles per hour if there are pedestrians and bicyclists using the facility and a history of crashes or the potential for them. The design of an RRFB installation needs to include features to improve the visibility of the crossing.
Back to Top
Inertial and Inclinometer Based Profiler Repeatability and Accuracy Using the IRI Model
Oregon DOT is transitioning to use the International Roughness Index (IRI) for an incentive\disincentive program for
pavement smoothness evaluation for newly paved roads. The IRI will typically be determined by contractors using inertial
profilers. This research evaluated the procedures, site, and equipment used for establishing a reference profile for a
certification process for inertial profilers. In a comparison of several profiling devices, the inclinometer-based profiler used
by Oregon DOT for the reference profile showed sufficient results in repeatability and accuracy in profile measurement and
calculation of IRI. However, the certification site shows significant variability in IRI across the site, which can lead to
lower accuracy scores when the exact path is not followed. Further, significant differences in IRI were observed during
repeat visits throughout the course of the study period.
This study also evaluated the use of a new technology, terrestrial laser scanning, for pavement analyses. At larger extents,
terrestrial laser scanning (TLS) was compared to several current techniques to measure road profiles including digital
levels, inclinometers, and inertial profilers. TLS is able to collect a large, dense set of data relatively quickly for the entire
roadway and surrounding areas; hence, the data can not only be used for evaluating the pavement roughness but also can be
used for other design parameters such as transverse and longitudinal slope. The results show that profiles derived from
TLS data determined accurate IRI values and cross-correlation with the reference profile. At a finer scale, micron
resolution 3D laser scanners can be utilized to determine the influence of predominant aggregate size on the texture of the
Naturally Occurring Hazardous Materials
Back to Top
The study of naturally occurring hazardous materials (NOHMs) was conceived as a proactive response to assure that the Oregon Department of Transportation (ODOT) maintenance and construction activities take the presence of NOHMs into account. The label of NOHM is given to certain elements, minerals, and materials of a varied geologic nature found in natural deposits or as contaminants that could have consequences on the well-being of those exposed to these earthy materials. Many elements, minerals (non-fuel and industrial minerals), and other rocks meet the NOHM criteria, particularly those that pose health hazards through their
physical properties (e.g., size, shape, dissolutions traits). It is when such an occurrence is disturbed, crushed, or exposed to natural weathering and erosion, or to human activities that create dust that a potential risk may arise and possibly pose a human health or environmental concern.
Out of 42 possible NOHMs, ODOT’s Technical Advisory Committee picked 16 for the project. Ten ODOT sites across Oregon were sampled for the presence (or absence) of any one of these NOHMs, from which 15 composited samples were collected. Of these, 4 samples were analyzed for multi-elements (35 analytes), 10 samples were examined for zeolite minerals with erionite being the mineral of interest, and 2 samples were examined for asbestos minerals. Five samples from four sites contained fibrous material in suspension. X-ray fluorescence diffraction (XRD) was unable to match the fibrous material with zeolite XRD pattern matching standards. However, Transmission Electron Microscopy (TEM) data of the fibrous material points to offretite’s chemistry field, a zeolite species closely associated with erionite or possibly a Mg-poor erionite. The incongruity between the XRD and TEM results tends to confound analytical interpretation and the results are unfortunately inconclusive. At two ODOT sites, multi-element analysis by ICP-AEA with trace Hg by Cold Vapor/AAS revealed elevated levels of As and other analytes. Anthophyllite and
chrysotile, both regulated asbestos minerals, were detected in two samples from the Chancellor quarry using NIOSH 9002 method (PLM/DS procedures).
A NOHM-GIS interpretative layer, called NGIL, is an important outcome of this project. It was developed to map where the 16 NOHMs picked for the project are likely to be encountered. To convey NOHM information to ODOT personnel, a relative NOHM
hazard potential was assigned to geologic unit polygons held in the Oregon Digital Geologic Compilation. The relative NOHM hazard potential is expressed in qualitative terms of ‘Most’, ‘Moderate’, or ‘Least’ likely. To arrive at a hazard classification, various data rules were devised based on geological factors, expert knowledge, and databases either developed or enhanced for the project. NGIL is also linked to a database of the characteristics, hazards, analytical methods, and precautions that are associated with each NOHM.
Development of a Guideline for Estimating Tsunami Forces on Bridge Superstructures
Back to Top
|The Pacific Northwest is vulnerable to seismic events in the Cascadia Subduction Zone (CSZ) that could generate a |
large tsunami that could devastate coastal infrastructure such as bridges. In this context, this paper describes the
development of a guideline for estimating tsunami forces on bridge superstructures along the Oregon Coast. A multiphysics
based numerical code is used to perform numerical modeling of tsunami impact on full-scaled bridge
superstructures of four selected bridges – Schooner Creek Bridge, Drift Creek Bridge, Millport Slough Bridge, and
Siletz River Bridge – located on Highway 101 in the Siletz Bay area on the Oregon Coast. Two different types of
bridge superstructure, deck-girder and box sections, are developed in the case of the Schooner Creek Bridge to study
the effect of geometry of bridge cross-section. The results show that tsunami forces on box section superstructures are
significantly higher than the forces on deck-girder sections; therefore, the box section design might not be appropriate
to be used in a tsunami run-up zone. Moreover, numerical simulation of a deck-girder bridge with rigid rails and with
open rail spacing, subjected to identical tsunami loads, was performed to examine the effect of rails on tsunami forces.
The results suggested that horizontal and vertical tsunami forces on bridges with rails are larger than those on bridges
with open rail spacing, up to 20% and 15%, respectively. These numerical results are finally incorporated into the
mathematical formulations from the existing literature to develop a simplified method for estimating tsunami forces on
bridge superstructures. Appropriate empirical coefficients for bridge superstructures under tsunami loads were
evaluated based on an average value of the scattering data from the numerical results. The developed guideline is
intended to be used as a preliminary guidance for design only as it did not account for uncertainties; thus, an
appropriate load factor must be included in the calculations. A previous analysis of tsunami forces on the Spencer
Creek Bridge on the Oregon Coast is revisited to examine the applicability of the guideline developed in the present
work. This paper also presents the results of a study on the optimal number of CPUs for running fluid-structure
interaction (FSI) numerical models of bridge superstructures using LS-DYNA on high-performance computing (HPC)
Replacing Thermal Sprayed Zinc Anodes on Cathodically Protected Steel Reinforced Concrete Bridges
Back to Top
|This research aimed to address questions underlying the replacement of arc-sprayed zinc anodes on cathodically |
protected steel reinforced concrete bridges and to develop a protocol to prepare the concrete surface for the new anode,
through a combination of literature review, practitioner surveys, laboratory studies, and field investigation (Pier 9 of the
Yaquina Bay Bridge, Oregon). Concrete with an equivalent electrochemical age of 5 to 45 years was found to have a
reaction layer of ~1 mm. To achieve strong initial bond strength of new zinc to the profiled concrete surface, the
current ODOT sandblasting operating configuration (#8 nozzle with high sand volume) is too aggressive and should be
changed to #6 nozzle with low sand volume to achieve target RMS macro-roughness of 1.2-2.1 centi-inches and microroughness
of 3.5-5 μm. It is recommended to adjust the anode removal and surface profiling based on the
electrochemical age of the existing concrete. Wherever possible, large aggregates (e.g., diameters ¾ in. and bigger)
should be avoided for exposure by surface profiling. For non-electrochemically aged concrete, the surface should be
profiled to achieve a RMS macro-roughness of 1.1-1.8 centi-inches and 5-36% exposed aggregates. For existing
concrete with relatively high electrochemical age (14 yrs), the surface should be profiled to achieve a RMS macroroughness
of 1.1-1.5 centi-inches and 44-55% exposed aggregates. The following recommendations were made for old
anode removal and surface preparation before new anode application: use a reasonably low air pressure and a
reasonably hard and dense abrasive material for sandblasting; have a reasonably thin coating per pass during arc-spray
operations; and have a slightly thinner overall Zn coating layer (15-17 mils vs. the currently used 17 mils). It is also
desirable to have concrete with good surface cohesion strength and a minimum of 150 psi initial bond strength. For
existing concrete with an equivalent electrochemical age of more than 8 years, the reaction layer should be completely
removed prior to profiling and arc spraying (e.g., 4 mm grinding).
Red Light Running Camera Assessment
Back to Top
|In the 2004-2007 period, the Mission Street SE and 25th Street SE intersection in Salem, Oregon showed relatively few crashes attributable to red light running (RLR) but, since a high number of RLR violations were observed, the intersection was identified as having a high crash potential. ODOT approved the installation of RLR cameras for a trial period to study the results of RLR cameras. Cameras were installed in February 2008 in the westbound and northbound directions. |
A before and after study of the crashes involving westbound and northbound drivers at the Mission and 25th intersection was completed. In the 50 months prior to the camera installation crashes averaged 0.62 per month. In the 21 months after installation, the average increased by 77.4% to 1.10 per month.
Crash cost estimates for different types of crashes make it possible to account for the expectation that RLR cameras are likely to result in fewer angle crashes, which are often severe, and more rear end crashes, for which injuries tend to be less severe. The estimated average monthly crash costs increased from $16,296 before the cameras were installed to $27,738 after the cameras were installed.
Crashes increased only slightly or not at all at two comparison intersections, whereas the crashes increased substantially at the Mission at 25th intersection. Since traffic volumes declined slightly from the pre- to post-installation periods, the crash data were not normalized.
After camera installation, violations decreased by 43 percent in the westbound direction and 23 percent in the northbound direction. At both the westbound and northbound approaches, left turning vehicles accounted for the overwhelming majority of the violations.
Fisheye and Image Stitching
Enhancements for Digital Imaging of Gusset Plate Connections: Fisheye and Image Stitching
Back to Top
|This report describes techniques to convert fisheye digital images of gusset plates to perspective images (defish). It also describes methods to stitch together partial images of a gusset plate into a composite of the complete gusset plate. The converted images can be used in rectification and metrification procedures to allow geometric measurements of the connection plates from the processed images. Software applications were written using Matlab to perform the image transformations. |
Assessment of Statewide Intersection Safety Performance
Back to Top
|This report summarizes the results of an analysis of the safety performance of Oregon’s intersections. Following a pilot study, a database of 500 intersections randomly sampled from around the state of Oregon in both urban and rural environments was assembled. These intersections were categorized into eight types based on number of legs (3 and 4), land use (urban or rural) and traffic control (signalized or minor stop-control). These categories were chosen to align with the intersection types in AASHTO’s recently released Highway Safety Manual (HSM). Geometric and traffic control elements were supplemented by compiling crash data and volumes on the major and minor approaches. The safety performance was analyzed by three primary methods. First, crash rates were calculated and analyzed for each of the intersection groups. Crash rates determined for Oregon intersections were generally well below rates found published for other states. Since it is unlikely that such a significant difference exists in the safety performance between states, it is more likely explanation is the different reporting thresholds and Oregon’s reliance on self-reporting. Second, crash patterns were tabulated for a number of crash and driver involved variables. These patterns, not before generated, will be very useful to improve identification of high crash intersection locations and improve diagnosis of these locations. Third, safety performance functions (SPFs) were created for intersections where sufficient data exist. For the purposes of this research SPFs were estimated for the rural 3-leg stop controlled and urban 4-leg signalized intersections. The SPFs developed in this modeling exercise were compared to the HSM base models calibrated to Oregon. The rural 3-leg stop models compare favorably. Within the volume range of the data used to generate the SPFs, the models compare well. The urban signalized intersection SPFs did not compare as well to the HSM base models. Further research is needed to investigate whether Oregon-specific SPFs have advantages over calibrated HSM models. The results of this analysis can be used to improve the diagnosis and identification of unusual safety performance at intersections in Oregon. The average rates are useful for peer comparisons and in calculation of critical rates. The crash patterns can be directly applied in diagnostic efforts to detect unusual patterns at intersections. The SPF modeling effort is the groundwork for further explorations and model development for Oregon facilities. |
Implementation Plan and Cost Analysis for Oregon's Online Crash Reporting System
Back to Top
|Federal, state and local transportation agencies, law enforcement, the legislature, consulting firms, safety advocates and the |
public use crash data to quantify emerging traffic safety issues and problems, determine priorities, support decision-making,
and target resources where they will be most effective. In most states, the primary source of crash data is a report completed
by police officers. Oregon is different in that it relies heavily on citizens to report crash data via the Oregon Traffic
Accident and Insurance (OTAI) paper-based report. Citizens are required to submit the OTAI report to the Driver and
Motor Vehicle Services (DMV) within 72 hours after the accident occurs.
The main objective of this project was to define the main features, functions, capabilities and system architectures that may
be incorporated into an online citizen crash reporting system to complement (and eventually replace) the paper-based OTAI
report. The implementation of an online citizen crash reporting system could translate into a number of potential benefits to
DMV and the Crash Analysis and Reporting (CAR) Unit. These benefits may include the collection of more accurate,
timely, uniform and complete traffic accident data. It is expected that the preliminary design work performed as part of this
project will aid the DMV and the CAR Unit in the future development and implementation of an online citizen crash
Open-Graded Wearing Courses in the Pacific Northwest
Back to Top
The Oregon Department of Transportation (ODOT) has been placing ¾-inch nominal maximum aggregate size (NMAS) open-graded wearing courses (OGWCs) in structural layers of two inches or more for about 30 years. Despite this, OGWC performance in the Pacific Northwest is not well understood. This study determines the use and performance of ODOT OGWCs with special attention given to ¾-inch open-graded HMA (previously referred to as “F-Mix”) and recommends guidelines for the future use of OGWCs.
The best estimated service life of ODOT ¾-inch open-graded HMA ranges from 14 years (< 5,000 ADT) down to 7 years (> 100,000 ADT), which is less than comparable dense-graded mixes. The primary mode of distress is raveling and studded tire wear. Reduced service life, along with uncertain and unquantified safety benefits and a possible greater risk of early failure lead to a recommendation to discontinue use of ¾-inch open-graded HMA in Oregon as a standard surface mix. OGWCs used elsewhere in the U.S. are not likely suited for ODOT use due to their susceptibility to studded tire wear and are not recommended for adoption. If ¾-inch open-graded HMA does continue in use, recommendations are: (1) quantify its benefits, (2) restrict its use to low traffic (< 30,000 ADT), (3) recalibrate PMS expected life to be more in line with observed historical life, and (4) require the use of a windrow pick-up machine or end-dump transfer machine when paving OGWC.
Assessment of the Socio-Economic Impacts of SB 1080 on Immigrant Groups
Back to Top
In July 2008, the State of Oregon implemented SB 1080, legislation that required all applicants for an Oregon Driver License or ID card to present proof of legal presence in the United States. In 2007, some 140,000 unauthorized immigrants were estimated to be living in Oregon, more than two-thirds of whom were estimated to be members of the labor force. Approximately 97% of Oregon’s unauthorized immigrants are thought to be Latino, nearly all of Mexican origin. This report includes a discussion of the social science findings on the situation of undocumented workers in the U.S and what is known about the uses of different forms of identification for Mexican nationals. It presents a statistical portrait of the Mexican-born population of Oregon, demonstrating their concentration in particular occupations, particularly agriculture, building and grounds maintenance, food preparation and construction. Given the magnitude of the ongoing recession, no economic impact of SB 1080 is yet discernible. In a full employment context, such as existed during 2007, and after all outstanding licenses held by undocumented immigrants have expired, SB 1080 might reduce state GDP by $160 million, or 0.1%, while raising wages by 0.16%. Economic impacts would be concentrated on those industries that particularly employ undocumented workers, notably agriculture and food service. Interviews with nearly 400 Spanish-speaking Oregon residents, conducted in the Summer of 2009, indicate distress and uncertainty in the Latino community, fear of deportation arising from a traffic stop, a significant number of people driving without a license and adjustments within households that reduce access to employment, education, medical and social services, church attendance and recreation. The full range and magnitudes of impacts cannot be known with certainty until SB 1080 is fully implemented in 2016, and the economy has recovered – and may be mitigated by immigration reform at the Federal level.
Factors for Improved Fish Passage Waterway Construction
Back to Top
|Streambeds are important fish passageways in Oregon; they provide for the necessary habitats and spawning cycles of a healthy fish population. Oregon state law requires that hydraulic structures located in water properly provide fish passage. Increasingly stringent state and federal regulations apply to these fish passageways, and designers must become more cognizant of conditions over a range of flows to accommodate fish movement and avoid expensive structural failure of these passageways. Fish passage structures are built when roads cross streambeds and may include culverts, or bridges. When these structures are built, the streambeds are re-created using a technique called “roughened channels”. Roughened channels are man-made stream channels utilized for re-creating the hydraulics necessary for adequate stream passage, and this may include new constructions or retrofits of older, inadequate structures. Mixtures of materials are used to construct the bed of roughened channels, ranging from fines such as sand, silt and gravel to coarse elements like cobbles and boulders. Fines are a critical element in limiting permeability of the constructed bed thus keeping stream flow at the surface of the roughened channel during low flow periods. This report discusses work of a research project designed to discover factors that are key to successful long-term implementation of fish passageways, especially focused on the construction process. |
Areas of inquiry postulated in this study are that failures experienced in actual installations may be due to inadequate range and/or mix of soil and rock material gradation; unexpected water velocity, especially during high flows; inadequate mixing of rock and soil materials during construction; and inadequate compaction of rock and soil materials during construction. This report suggests that several factors may be especially important considerations in fish passage success. These factors are the relationship of downstream slope to structure slope, well-graded fine soil materials in the channel fill (improved by choice of fill source), and frequent site visits. Improving fish passages for cost-efficient fish movement is a priority for government agencies such as Oregon Department of Transportation (ODOT) and Oregon Transportation Research and Education Consortium (OTREC).
Safety Evaluation of Curve Warning Speed Signs
Back to Top
|This report presents a review of a research effort to evaluate the safety implications of advisory speeds at horizontal curve locations on Oregon rural two-lane highways. The primary goals of this research effort were to characterize driving operations at rural two-lane highway curve locations where advisory speed signs were present, and to determine to what extent these signs play a role in enhancing safety. Placement of advisory speed signs at horizontal curve locations in the State of Oregon is a practice aided by unique and specific state-level policies and, as such, may vary from nationally accepted procedures. |
Speed data was collected at 16 sites and compliance with advisory speed signs determined. An evaluation of site crash data and how advisory speed relates to historic crash information is included along with a statistical model that identifies critical variables that are associated with the posted speed and how they ultimately relate to the expected crash frequency.
The research team developed a statistically based advisory speed model that assesses predicted crash outcomes based on a combination of geometric design, operations, and signage. The resulting advisory speed models were then contrasted to the expected advisory speeds based on the Oregon Policy as well as the 2009 MUTCD thresholds. They determined that the safety-based model actually predicted advisory speeds that are not as conservative as those recommended using the ball-bank thresholds in the 2009 MUTCD or those identified using the thresholds Oregon has been using.
Just prior to publication of this report, the Oregon Traffic Control Devices Committee (OTCDC) decided to adopt the 2009 MUTCD without making an exception to advisory speed posting guidelines. ODOT has begun to transition to the 2009 MUTCD advisory speed posting criteria. Actual adoption of the 2009 MUTCD is expected to occur in August 2011.