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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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    <item>
      <title>Development of Crash Modification Factors and Functions for Widening Shoulder Width on Rural Two-Lane Roadways</title>
      <link>https://trid.trb.org/View/1522959</link>
      <description><![CDATA[This study assesses the safety effectiveness of widening shoulder width in reducing crashes on roadway segments. Generally, a crash modification factor (CMF) represents the overall safety performance of specific treatment in a single value. Although many researchers have estimated CMFs for various treatments (or countermeasures), there is a lack of prior studies that explored the variation of CMFs with different roadway characteristics among treated sites. Therefore, the study develops crash modification functions (CMFunctions) to determine the relationship between safety effects and different roadway characteristics among treated sites. This study first evaluates the CMFs for widening shoulder width using the observational before-after with empirical Bayes (EB) method to check overall safety effects. Secondly, the CMFs were calculated for each treated site based on different roadway characteristics such as original shoulder width of treated sites in before period and actual widened width. Lastly, the variation of CMFs was determined through developing CMFunctions. Crash and roadway characteristic data was collected for rural two-lane roadways in Florida, and the Florida-specific full SPFs for different crash types and severity levels were developed and used for the observational before-after with EB estimation.]]></description>
      <pubDate>Thu, 26 Jul 2018 14:42:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/1522959</guid>
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    <item>
      <title>Daily Changes in Roughness on LTPP SPS-2 Test Sections</title>
      <link>https://trid.trb.org/View/1337468</link>
      <description><![CDATA[The Long Term Pavement Performance (LTPP) program collected 140 sets of 5 repeat profile measurements on nine of the remaining 13 Special Pavement Studies (SPS-2) test sections to evaluate the change in daily roughness on the SPS-2 test sections which are plain jointed, doweled pavements with 15 ft joint spacing. Profile measurements were obtained at three intervals during the day ranging in duration between 8 hrs and 14 hrs. The average daily change in roughness (MRI) was 12 in./mi with extremes to 38 in./mi. The design feature which had the greatest impact on daily roughness change was flexural strength. The higher flexural strength produced a 30% higher average daily change. The Permeable Asphalt Treated Base (PATB) provided the best mitigation to daily roughness changes and it appears there may be some benefit to the widened shoulder concept for controlling daily roughness changes.]]></description>
      <pubDate>Sat, 24 Jan 2015 17:08:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/1337468</guid>
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      <title>A revised technical foundation for cross section for rural roads in Queensland</title>
      <link>https://trid.trb.org/View/1223422</link>
      <description><![CDATA[Transport and Main Roads (TMR) has traditionally used narrower cross sections than Austroads, but with fully sealed shoulders. In 2003, Austroads shoulder widths were &lsquo;rationalised&rsquo; via a conservative interpretation of the range of widths. These were not adopted by TMR. Since the Austroads Guide to Road Design (2009) was published, TMR have moved to adopting national standards as far as practical. However some TMR regional staff again believe that the rural two-lane, two-way cross section widths of Austroads are too conservative (i.e. too wide) in order to be affordable in Queensland. They believe that these widths do not offer good value for money as a narrower cross section would allow them to build or upgrade longer lengths of road. Rather than simply retaining current TMR practice without question, it was decided to see if a more rigorous technical foundation could be developed for rural two-lane, two-way cross section widths and in particular, incorporate safety relationships that supported any new design criteria. Interviews were also conducted with construction staff to understand and confirm the affordability and construction impacts. The conclusion of this paper makes recommendations about the rural cross section dimensions for use in Queensland, based on a more rigorous technical foundation that includes safety, affordability and constructability. The new criteria also take into account TMR cycling policy.]]></description>
      <pubDate>Tue, 27 Nov 2012 15:52:46 GMT</pubDate>
      <guid>https://trid.trb.org/View/1223422</guid>
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    <item>
      <title>Correlation of Accident Rates and Roadway Factors</title>
      <link>https://trid.trb.org/View/1219452</link>
      <description><![CDATA[The primary purpose of this study was to investigate the correlation between motor vehicle accidents and roadway  factors in the State of Indiana. The roadway factors evaluated were annual average daily traffic volume, capacity, congestion index, number of lanes, lane shoulder width, horizontal alignment, and number of entrances per mile. The factor of number of lanes, however, was eliminated early in the study because of the predominant mileage of two-lane highways. The accident rates used in the study were number of fatalities per mile, number of non-fatal accidents per mile, total number of accidents per mile and total number of accidents per one million vehicle miles on the State Rural Primary System for the two-year period 1954 and 1955. Only non-intersectional accidents were used. The results of the analysis revealed that there were positive and linear relationships between annual average daily traffic volume, congestion index, lane width and total number of entrances per mile with total number of accidents per roadway mile for the two year period of 1954 and 1955. A regression equation was also developed in an attempt to predict the number of accidents per mile by the use of the significant factors.]]></description>
      <pubDate>Tue, 20 Nov 2012 13:02:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/1219452</guid>
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    <item>
      <title>Design and maintenance strategies for a rural road system</title>
      <link>https://trid.trb.org/View/1194288</link>
      <description><![CDATA[Australian state road authorities are confronted with the problem of upgrading and strengthening an ageing existing road system and concurrently extending the system, at a time when the funds available for road construction are very limited.  The road planner's dilemma is one of obtaining a balance between demands, standards and funds with respect to the system as a whole and individual lengths of the system, taking into consideration present and future costs and funding levels.  This note discusses the financial implications of various alternative designs and maintenance strategies considered for the rural road system by the main roads department, Queensland.  It is concluded that pavements should be designed for longer rather than shorter design lives. In certain circumstances, measures other than increasing pavement thickness may be the most cost effective way of extending pavement life (a).]]></description>
      <pubDate>Fri, 24 Aug 2012 13:49:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/1194288</guid>
    </item>
    <item>
      <title>Design and maintenance strategies for a rural road system</title>
      <link>https://trid.trb.org/View/1193511</link>
      <description><![CDATA[Various design and maintenance strategies for the Queensland state rural road system have been examined.  It is concluded that pavements should be designed for longer rather than shorter design lives.  In certain circumstances, measures other than increasing pavement thickness may be the most cost effective way of extending the pavement life.  It is preferable to achieve economies in the width of construction rather than the depth of pavement.  Tolerable geometric standards need to be developed so as to ensure the greatest possible use of existing construction when strengthening or rehabilitating existing roads.]]></description>
      <pubDate>Fri, 24 Aug 2012 13:21:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/1193511</guid>
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      <title>Analysis of accident experience vs shoulder width</title>
      <link>https://trid.trb.org/View/1181389</link>
      <description><![CDATA[]]></description>
      <pubDate>Fri, 24 Aug 2012 03:24:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/1181389</guid>
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    <item>
      <title>Analysis of accidents of vehicles leaving the road</title>
      <link>https://trid.trb.org/View/1163793</link>
      <description><![CDATA[]]></description>
      <pubDate>Thu, 23 Aug 2012 14:25:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/1163793</guid>
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    <item>
      <title>Relating roadside collisions to highway clear zone width</title>
      <link>https://trid.trb.org/View/1154739</link>
      <description><![CDATA[This paper provides a quantification of the relationship between clear zone width and collision reduction that should provide key input into the process of selecting highway design standards.  The results show that single-vehicle run-off-road collision rates are reduced by approximately 40 per cent when the clear zone is increased from less than 6 metres to between 6 and 10 metres.  When the clear zone was extended to greater than 10 metres the collision rate was reduced by over 60 per cent.]]></description>
      <pubDate>Wed, 22 Aug 2012 21:57:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/1154739</guid>
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    <item>
      <title>Utilizing Automated Data Collection Vehicle Measurements in Determining the
Fore Slopes of Shoulders</title>
      <link>https://trid.trb.org/View/1143042</link>
      <description><![CDATA[The Wyoming Department of Transportation has an interest in collecting automated data on pavement shoulders. Such data would include shoulder width, type, as well as slope. Pathway Services Inc. has been collecting Pavement Management Systems (PMS) data on roadways in Wyoming, and indicated they had the ability to measure the transverse profile of ten to twenty feet from the white strip shoulder marking. Pathway Services has offered to provide measurements on test sections in Wyoming since they had not collected such data for any other states, so it was important to them to determine the limitations or potential of the system. The test sections included seventy miles of Wyoming highways with shoulder widths varying from zero to ten feet in two foot increments. Vegetation observations were made by researchers from the Wyoming Technology Transfer Center-Local Technical Assistance Program on the same day when Pathway’s data was collected to ensure identical conditions. It was found that the section with no shoulder had the most vegetation and the most varied slope measurements. It was concluded that vegetation does affect the accuracy of the sensor and that the sensor could not read past the pavement taper. In addition, the manually collected slope measurements and the automated slope measurements were statistically different on most of the sections included in the experiment.]]></description>
      <pubDate>Fri, 20 Jul 2012 15:21:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/1143042</guid>
    </item>
    <item>
      <title>Development of Accident Modification Factors for Rural Frontage Road Segments in Texas Using Generalized Additive Models</title>
      <link>https://trid.trb.org/View/1090350</link>
      <description><![CDATA[The objective of this study consists of assessing the application of generalized additive models (GAMs) for estimating accident modification factors (AMFs). GAMs are a new type of model that has been recently introduced by the statistical community for modeling observed data. These models offer more flexible functional forms than traditional generalized linear models and allow for more adaptable variable interactions. As recently documented in the literature, variable interactions should be included in the development of AMFs. To accomplish the study objective, AMFs were derived from GAMs using data collected on rural frontage roads in Texas. The AMFs were then compared to the AMFs produced from a previous study using the same data set. The results of the study show that AMFs produced from GAMs are more flexible to characterize the safety effect of simultaneous changes in geometric and operational features (or variable interactions) than when independent AMFs are applied together. The results also show that GAMs indicated a nonlinear relationship between crash risk and changes in lane and shoulder widths for frontage roads in Texas.]]></description>
      <pubDate>Wed, 16 Feb 2011 13:41:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/1090350</guid>
    </item>
    <item>
      <title>Post–Soil Interactions on Guardrails Near the Crown of a Slope: Theoretical Aspects</title>
      <link>https://trid.trb.org/View/1089718</link>
      <description><![CDATA[Most highway departments are very concerned with the adequacy of highway guardrails. A common problem is a narrow road shoulder of 1.5 m to 0.5 m, or even less, combined with steep side slopes and a high embankment beside the road. Although numerous studies have measured the strength of different types of guardrail posts in various soils, a theoretical model does not exist that could be used to predict soil resistance to post movement. Such a theoretical model was constructed for level ground as well as close to an embankment slope. A mechanical model of a narrow vertical object moving soil with a level surface was modified to account for a ground slope that lies within the area of influence of soil failure. The model predicts that at any distance from a slope, the resistance of a post can be increased by installing it to a greater depth. Also, when soil adjacent to a post is compacted heavily, it results in approximately a fourfold increase in horizontal resistance compared with a lightly compacted soil. A rough surface post, such as concrete, gives almost double the horizontal resistance of a smooth surface post of the same dimensions. Using a post of 400 mm width rather than 100 mm results in a horizontal soil resistance force of only approximately 20% to 30%, for a post far away from or very close to the crown of a slope of 1 vertical/2 horizontal.]]></description>
      <pubDate>Mon, 31 Jan 2011 13:02:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/1089718</guid>
    </item>
    <item>
      <title>Effects of Horizontal Curvature on Single-Vehicle Motorcycle Crashes Along Rural Two-Lane Highways</title>
      <link>https://trid.trb.org/View/910123</link>
      <description><![CDATA[Motorcycle crashes and fatalities have been increasing rapidly during the past 12 years both in Ohio and across the rest of the United States. In response to these issues, various studies have examined aspects of motorcycle safety in recent years. However, there has been limited research on the effects of site-specific roadway geometry on the frequency of motorcycle crashes, particularly at nonintersection locations. Typically, researchers employ Poisson and negative binomial crash prediction modeling techniques in these types of studies. The research presented in this paper uses a negative binomial model, applying full Bayes methods to improve model performance and to assess the impacts of horizontal curvature and other geometric features on the frequency of single-vehicle motorcycle crashes along segments of rural two-lane highways. The data used in this study include crash records for the years 2002 through the spring of 2008, in combination with available geometric design information, for those curves maintained by the State of Ohio. The analysis data set includes 30,379 horizontal curves that experienced a total of 225 motorcycle crashes during the study period. The findings show that the radius and length of each horizontal curve significantly influence the frequency of motorcycle crashes, as do shoulder width, annual average daily traffic, and the location of the road segment in relation to the curve.]]></description>
      <pubDate>Wed, 31 Mar 2010 07:45:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/910123</guid>
    </item>
    <item>
      <title>Studies to Determine the Operational Effects of Shoulder and Centerline Rumble Strips on Two-Lane Undivided Roadways</title>
      <link>https://trid.trb.org/View/900768</link>
      <description><![CDATA[This report describes the methodology and results of analyses performed to (1) evaluate the impact of shoulder rumble strips (SRS) and centerline rumble strips (CRS) on the placement of vehicles in the travel lane of two-lane, undivided roadways and (2) determine the minimum shoulder width required for drivers to correct errant vehicle trajectories once alerted by passing over SRS. Field studies indicated that CRS on two-lane, undivided roadways with lane widths as narrow as 10 ft do not adversely impact the lateral placement of the vehicle in the travel lane. In fact, at locations with smaller shoulder widths (1 to 2 ft) drivers positioned the center of their vehicles closer to the center of the lane. Similar effects were found at locations with both edgeline rumble strips (ERS) and CRS. The impact of SRS located within 7 to 9 inches of the edgeline on the lateral placement of vehicles in the travel lane was less clear. However, it does appear that SRS located near the edgeline may shift vehicle travel paths closer to the centerline. In contrast, SRS located 35 inches from the edgeline did not seem to impact the lateral placement of vehicles in the travel lane. In addition, lateral offsets that position the center of 16-in. SRS in the middle of the shoulders at least 4-ft wide should provide enough remaining shoulder width for the 85th percentile distracted driver to correct their errant vehicle trajectory before leaving the paved roadway surface. Additional findings from all of the studies and detailed recommendations are discussed in the report.]]></description>
      <pubDate>Mon, 21 Sep 2009 08:44:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/900768</guid>
    </item>
    <item>
      <title>Safety Data, Analysis, and Evaluation 2009, Volume 2</title>
      <link>https://trid.trb.org/View/899331</link>
      <description><![CDATA[These 13 papers are concerned with safety data, analysis and evaluation.  Specific topics discussed include the following:  calibration of the Highway Safety Manual's accident prediction model for a secondary road network; speed and safety; accident modification functions; elementary units of exposure; identifying crash hot spots; safety of lane and shoulder width combinations on rural roads; effects of pavement marking retroreflectivity on traffic crash frequency; road data aggregation and sectioning for crash analysis; safety evaluation of curve delineation improvements; microsimulation to study a traffic signal incident reduction function; comparison of simulated freeway safety performance with observed crashes; traffic operation measures in the safety analysis of signalized intersections; and different parameterizations of the varying dispersion parameter as a function of segment length.]]></description>
      <pubDate>Fri, 28 Aug 2009 16:21:02 GMT</pubDate>
      <guid>https://trid.trb.org/View/899331</guid>
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