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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <language>en-us</language>
    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Evaluating the impact of self-luminous road markings on driver behavior at unsignalized intersections: A simulator study</title>
      <link>https://trid.trb.org/View/2517271</link>
      <description><![CDATA[Unsignalized intersections are accident-prone locations due to numerous conflict points and unclear right-of-way. This issue is exacerbated at night when road markings become less visible, leading to increased accident rates. Self-luminous road markings, a new type of proactive traffic safety control facility, have garnered increasing attention and are being gradually promoted due to their intelligent, stable brightness and variable characteristics. To explore the warning effect of self-luminous road markings at unsignalized intersections at night, this study designed three types of warning schemes: continuous-illuminating pedestrian crosswalk advance warning marking (CPWM), continuous-illuminating yield text advance warning marking (CYWM), and transition-illuminating pedestrian crosswalk advance warning marking (TPWM). Based on previous research, nine indicators were selected for comprehensive evaluation from the perspectives of driver’s operating, visual characteristics, and psychology. Finally, an entropy-based matter-element model was constructed to comprehensively evaluate the warning effect. The results show that the CYWM and CPWM schemes can help drivers effectively reduce the mean speed and potential lateral conflict risk at intersections, enhancing drivers’ awareness of road environment information. However, the TPWM scheme had adverse effects due to greater visual stimulation. The effectiveness of the three schemes ranks from high to low as CYWM, CPWM, and TPWM. This study confirms that self-luminous road markings are effective at intersections, providing new insights for infrastructure upgrades and offering a general framework for evaluating the effectiveness of traffic safety facilities.]]></description>
      <pubDate>Tue, 08 Apr 2025 09:17:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2517271</guid>
    </item>
    <item>
      <title>Mesopic conditions optimise the detection of visual function loss in drivers with simulated media opacity</title>
      <link>https://trid.trb.org/View/2006286</link>
      <description><![CDATA[Drivers have different visual demands across varying contrast and luminance conditions. However, vision assessments for driving are typically conducted under photopic conditions. This study investigated the sensitivity of photopic and mesopic conditions to detect contrast sensitivity (CS) loss in drivers with simulated media opacities. CS was measured in forty-seven healthy drivers aged 18-50 years (mean +/- SD: 25.5 +/- 6.5) under photopic and mesopic-adapted luminance levels with the Pelli-Robson chart and the Mesotest II (without glare). Media opacities were simulated using white-opacity containing Lee Fog filters (1-5) and CS measured in a randomized order. A significant (p < 0.001) reduction in photopic CS (logCS) was measured with the Pelli-Robson chart only when media opacity was simulated with Fog filter 5 (1.53 +/- 0.15, 2.8 triplets reduction) compared to baseline (1.95 +/- 0.03). Mean mesopic CS demonstrated a significant (all p < 0.001) reduction from baseline (1.67 +/- 0.14) for Fog filters 3 (1.4 triplets, 1.45 +/- 0.16), 4 (2.4 triplets, 1.31 +/- 0.14) and 5 (4.3 triplets, 1.02 +/- 0.15). For Mesotest II, only Fog filter 5 produced a significant reduction (0.10 +/- 0.09; p < 0.001) in mean mesopic CS from baseline (0.30 +/- 0.01). Mesopic CS is more vulnerable to different levels of simulated media opacity, hence should be considered clinically when assessing visual function in older drivers at risk of media opacity.]]></description>
      <pubDate>Fri, 14 Oct 2022 08:53:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2006286</guid>
    </item>
    <item>
      <title>Independent Component Analysis of Combustion Images in Optically Accessible Gasoline and Diesel Engines</title>
      <link>https://trid.trb.org/View/1828858</link>
      <description><![CDATA[Flame luminosity fields can nowadays be collected from optically accessible engines, with high spatial and temporal resolution, and constitute a very powerful investigation means for the transient combustion phenomena taking place in the engine chamber. Interpretation of the impressive amount of collected data can be quite challenging, mainly due to the variety of coupled phenomena involved. Application of Independent Component Analysis (ICA) aims here at separating spatial structures related to different combustion events, and is coupled with the analysis of the statistics of the coefficients of the independent components, and of the measured in-cylinder parameters. This paper reports on the comparison of the application of ICA to 2D images of combustion-related luminosity collected from two different optically accessible engines: Diesel and spark ignition. Independent components and their coefficients are first extracted from sets of luminosity images, and then used to identify leading structures and to study the transient behavior of the combustion process. The two components identified from the single Diesel cycle appear to be clearly related to early combustion along the fuel jets and later combustion near the bowl walls, respectively; quantitative analysis of coefficient statistics confirms the lower variability of the jet flames with respect to combustion near the chamber walls. The same can be said of the results of the analysis for SI combustion images, which are separated in early, median and final luminous combustion. The analysis is fast and reliable and can be prospectively applied to many different optical engine configurations.]]></description>
      <pubDate>Fri, 15 Apr 2022 17:16:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/1828858</guid>
    </item>
    <item>
      <title>Two-Colour Pyrometry Measurements of Low-Temperature Combustion using Borescopic Imaging</title>
      <link>https://trid.trb.org/View/1847678</link>
      <description><![CDATA[Low temperature combustion (LTC) of diesel fuel offers a path to low engine emissions of nitrogen oxides (NOᵪ) and particulate matter (PM), especially at low loads. Borescopic optical imaging offers insight into key aspects of the combustion process without significantly disrupting the engine geometry. To assess LTC combustion, two-colour pyrometry can be used to quantify local temperatures and soot concentrations (KL factor). High sensitivity photo-multiplier tubes (PMTs) can resolve natural luminosity down to low temperatures with adequate signal-to-noise ratios. In this work the authors present the calibration and implementation of a borescope-based system for evaluating low luminosity LTC using spatially resolved visible flame imaging and high-sensitivity PMT data to quantify the luminous-area average temperature and soot concentration for temperatures from 1350-2600 K. The visible flame area is used to adjust the PMT measurements to account for sooting area (i.e., the fraction of the region of interest that contains discernible flame/natural luminosity). The validity of the approach is assessed using spatially resolved temperature and soot concentration data collected from a full optical single-cylinder engine operating using non-premixed natural gas combustion, with soot concentrations similar to those seen in the LTC data. The high sensitivity and low noise of the PMTs, combined with the broad field of view of the borescope, and the proposed sooting area correction method, provide robust measurement of flame temperature and KL factor in low temperature and low-sooting combustion conditions. Whilst the sooting area correction is found to have only a small effect on the measured temperature, it is shown to be important to provide soot concentrations that are representative of spatially resolved results. This work provides new insights into the use of relatively low-cost, high sensitivity PMTs to assess advanced and low-emission combustion systems.]]></description>
      <pubDate>Tue, 26 Oct 2021 14:30:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/1847678</guid>
    </item>
    <item>
      <title>Luminosity and Thermal Energy Measurement and Comparison of a Dielectric Barrier Discharge in an Optical Pressure-Based Calorimeter at Engine Relevant Conditions</title>
      <link>https://trid.trb.org/View/1847679</link>
      <description><![CDATA[The amount of the thermal energy released in a gas mixture is crucial to characterize the igniter capability to start a robust ignition in internal combustion engines, especially in challenging operating conditions as high EGR dilution or very lean mixture. Nevertheless, the thermal energy measurement can be performed only in controlled environments, such as constant volume vessels, while it is not feasible in metal engines. This work proposes to find a correlation between the released thermal energy and the luminosity generated by the same discharge event in an optical vessel. This correlation implies that energy information could be indirectly obtained through feasible optical measurements in optical engines, and even in metal engines via low-cost diagnostic tools such as borescopes. The experimental campaign is carried out with a non-equilibrium plasma igniter, a dielectric-barrier discharge igniter (BDI). This choice is due to the inherent igniter features (i.e., the development of a volumetric discharge and the capability to modulate the discharge intensity) that makes it suitable for the purpose of the proposed campaign. Pure nitrogen, at engine-relevant pressure, is used as medium inside the vessel. The electrode voltage is varied from inception to the highest value allowed; a sweep of discharge duration is performed as well.]]></description>
      <pubDate>Wed, 20 Oct 2021 09:25:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/1847679</guid>
    </item>
    <item>
      <title>The impact of intake pressure on high exhaust gas recirculation low-temperature compression ignition engine combustion using borescopic imaging</title>
      <link>https://trid.trb.org/View/1861091</link>
      <description><![CDATA[In diesel engines, high levels of exhaust gas recirculation can be used to achieve low-temperature combustion, resulting in low emission levels of both nitrogen oxides (NOₓ) and particulate matter. This work studied the effects of varying the intake manifold pressure on in-cylinder combustion processes and engine-out emissions from a light-duty single cylinder diesel engine under conventional and high exhaust gas recirculation low-temperature combustion regimes. The work was conducted at a part-load cruise condition of 1500 r/min and at an indicated mean effective pressure of approximately 600 kPa. Exhaust gas recirculation rates were varied between 0% and 65% at absolute intake pressures of 100–150 kPa. Very low NOₓ  emissions were achieved (<10 ppm, ∼0.05 g/kW h) for intake oxygen mass fractions below about 11%, independent of boost pressure. Smoke emission levels were lower than for non–exhaust gas recirculation combustion at oxygen mass fractions below ∼9%, depending on the boost pressure. High intake pressures reduced fuel consumption by 15% and combustion by-product emissions by 50%–60% compared to low boost. For the low intake boost case, little visible flame was apparent through borescope imaging. At higher boost pressures, intense flame luminosity was observed within the piston bowl early in the expansion stroke. Spatially averaged soot luminosity based on photomultiplier tube data showed that peak soot luminosity was five times greater and occurred 8 °CA earlier for high boost. This work demonstrates how the combination of appropriate boost pressures and exhaust gas recirculation rates can be used to mitigate the emissions and thermal efficiency penalties of high-dilution low-temperature combustion to achieve near-zero NOₓ operation.]]></description>
      <pubDate>Fri, 27 Aug 2021 14:58:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/1861091</guid>
    </item>
    <item>
      <title>Bright Investments: Measuring the Impact of Transport Infrastructure Using Luminosity Data in Haiti</title>
      <link>https://trid.trb.org/View/1727176</link>
      <description><![CDATA[This paper quantifies the impacts of transport infrastructure investments on economic activity in Haiti, using satellite night-light luminosity as a proxy measure. The authors' identification strategy exploits the differential timing of rehabilitation projects across various road segments of the primary road network. The authors combine multiple sources of non-traditional data and carefully address concerns related to unobserved heterogeneity. The results obtained across multiple specifications consistently indicate that receiving a road rehabilitation project leads to an increase in luminosity values of between 6% and 26% at the communal section level. Taking into account the national level elasticity between luminosity values and GDP, the authors approximate that these interventions translate into communal section-GDP increases of between 0.5% and 2.1%, for communal sections benefited by a transport infrastructure project. They observe temporal and spatial variation in results, and crucially that the larger impacts appear once projects are completed and are concentrated within 2 km buffers around the intervened roads. Neither the richest or the poorest communities reap the benefits from road improvements, with gains accruing to those in the middle of the ranking of communal sections, based on unsatisfied basic needs. The authors' findings provide novel evidence on the role of transport investments in promoting economic activity in developing countries.]]></description>
      <pubDate>Tue, 22 Sep 2020 14:27:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/1727176</guid>
    </item>
    <item>
      <title>Correlation of nanoparticle size distribution features to spatiotemporal flame luminosity in gasoline direct injection engines</title>
      <link>https://trid.trb.org/View/1723407</link>
      <description><![CDATA[Particle size distribution measured by mobility instruments is a common diagnostic used to characterize ultrafine and nanoparticle emissions in engine exhaust; however, some features of particle size distribution data are poorly correlated to in-cylinder combustion phenomena. In this work, in-cylinder spatiotemporal flame luminosity is quantitatively correlated to features in the solid particle size distribution measured in the exhaust of a gasoline direct injection engine operating in lean and stoichiometric combustion modes. A multi-channel optical sensor was used to measure diffusion flame light intensity in different areas of the combustion chamber. Total solid particle number and particle size distribution in the exhaust were measured using a scanning mobility particle sizer after a catalytic stripper that removed semi-volatile compounds. Results of the experiments showed that different flame phenomenon resulted in distinct particle size distribution characteristics. A large accumulation mode (particles with diameter of 50–100 nm) in the particle size distribution from stoichiometric engine operation with early injection resulted from anomalous diffusion flames like piston-top pool fires. In lean operation incorporating a secondary fuel injection, particle emissions were dominated by flame propagation through fuel-rich regions of the combustion chamber resulting in a comparatively broad particle size distribution. More generally, this work illustrates how particle size distribution data can be more accurately used to diagnose soot formation in gasoline direct injection engines.]]></description>
      <pubDate>Mon, 24 Aug 2020 09:28:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/1723407</guid>
    </item>
    <item>
      <title>LED Traffic Signal Luminosity Study</title>
      <link>https://trid.trb.org/View/1704620</link>
      <description><![CDATA[The objective of this study is to conduct a life-cycle analysis and reconnaissance of the “degradation rate” of light emitting diode (LED) traffic signal heads in Alaska. Project includes literature review, data collection, data analysis, reporting, and recommendations for optimizing LED signal head replacement.]]></description>
      <pubDate>Mon, 04 May 2020 15:49:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/1704620</guid>
    </item>
    <item>
      <title>Natural Flame Luminosity and Emission Spectra of Diesel Spray Flame under Oxygen-Enriched Condition in an Optical Constant Volume Vessel</title>
      <link>https://trid.trb.org/View/1562090</link>
      <description><![CDATA[The application of oxygen-enriched or oxy-fuel combustion coupled with carbon capture and storage technology has zero carbon dioxide emission potential in the boiler and gas turbine of the power plant. However, the oxygen-enriched combustion with high oxygen level has few studies in internal combustion engines. The fundamental issues and challenges of high oxygen level are the great differences in the physical properties and chemical effects compared with the combustion in air condition. As a consequence, the diesel spray combustion characteristics at high oxygen level were investigated in an optical constant volume vessel. The oxygen volume fraction of tested gas was from 21% to 70%, buffered with argon. The high-speed color camera was used to record the natural flame luminosity. It is found that with the rising of oxygen level, the period from the start of injection to the end of combustion shortened, the luminosity intensity in the flame core increased and the shape of the spray flame was shortened and narrowed. Meanwhile, an obviously blue region appeared at the tip of flame when the oxygen level was up to 60% or higher. To study the interesting blue region, the one-dimensionally resolved diesel spray flame emission spectra were investigated along the vertical axis of the spray. Results show that the transition point of the flame configuration was around 70 mm from the nozzle tip. Soot radiation dominated the flame natural luminosity in the range of 0-70 mm from the nozzle, while the chemiluminescence of carbon monoxide oxidation dominated in the range of 70-100 mm. For further consideration, in high oxygen level, the soot existing region is shortened and CO as well as UHC is oxidized more completely. Meantime, there is no NOx emission from the fuel combustion in nitrogen-free environment. Therefore, oxygen-enriched combustion will help to achieve the improvement of high efficiency and low emissions in internal combustion engines.       ]]></description>
      <pubDate>Tue, 25 Jun 2019 09:57:20 GMT</pubDate>
      <guid>https://trid.trb.org/View/1562090</guid>
    </item>
    <item>
      <title>Diffuse Back-Illuminated Extinction Imaging of Soot: Effects of Beam Steering and Flame Luminosity</title>
      <link>https://trid.trb.org/View/1580289</link>
      <description><![CDATA[This study presents diagnostic development of diffuse back-illuminated extinction imaging of soot. The method provides high temporal and spatial resolution of the line-of-sight optical density of soot (KL) in compression-ignited fuel sprays relevant to automotive applications. The method is subjected to two major sources of error, beam steering effects and broadband flame luminosity effects. These were investigated in detail in a direct injection combustion chamber with diesel fuel, under high and low sooting conditions. A new method for correcting flame luminosity effects is presented and involves measuring the flame luminosity using a separate high-speed camera via a beam splitter. The new method and existing methods are applied and the resulting flame luminosity correction errors are compared. The new method yields 50% lower errors than the most promising method (optical flow method). The impact on KL was investigated, showing that the KL uncertainty when using the optical flow method is unbounded for KL values above 2.7, while the new method has an uncertainty of 0.5 for the maximum KL value of 3.8. The new method yields overall lower uncertainties and is more suited to measuring KL in optical thick conditions. Large refractive index gradients in the path of the incident light cause false attenuation, resulting in ambiguity of the measured KL, referred to as beam steering. A detailed investigation of the beam steering effects caused by the non-uniformities in the diffused light source was performed. A beam steering model was made and qualitatively validated from experiments. The results from the beam steering model showed the importance of having a large collection angle, in order to average out small-scale non-uniformities in the light source. The model also showed that large-scale non-uniformities in the light source could affect the measurement even if the collection angle is large.       ]]></description>
      <pubDate>Fri, 22 Feb 2019 17:08:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/1580289</guid>
    </item>
    <item>
      <title>Guidelines for Interpreting Soot Luminosity Imaging</title>
      <link>https://trid.trb.org/View/1461418</link>
      <description><![CDATA[One way to develop an understanding of soot formation and oxidation processes that occur during direct injection and combustion in an internal combustion engine is to image the natural luminosity from soot over time. Imaging is possible when there is optical access to the combustion chamber. After the images are acquired, the next challenge is to properly interpret the luminous distributions that have been captured on the images. A major focus of this paper is to provide guidance on interpretation of experimental images of soot luminosity by explaining how radiation from soot is predicted to change as it is transmitted through the combustion chamber and to the imaging. The interpretations are only limited by the scope of the models that have been developed for this purpose.         The end-goal of imaging radiation from soot is to estimate the amount of soot that is present. The method selected for making such estimates is to model the combustion and sooting events with computational fluid dynamics (CFD), post-process the CFD results to generate 3D distributions of the soot-radiation field, model the transformation of the 3D distribution to a 2D distribution that is representative of luminosity captured by the camera, derive a relationship between the projected 2D luminosity and the amount of CFD-predicted in-cylinder soot, and finally, apply that relationship to experimental images thus giving an estimate of actual amount of in- cylinder soot that is present. Model descriptions, how the models are implemented and results of their application are included in this paper.       ]]></description>
      <pubDate>Wed, 28 Jun 2017 14:39:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/1461418</guid>
    </item>
    <item>
      <title>Simultaneous Measurement of Natural Flame Luminosity and Emission Spectra in a RCCI Engine under Different Fuel Stratification Degrees</title>
      <link>https://trid.trb.org/View/1461416</link>
      <description><![CDATA[Reactivity controlled compression ignition (RCCI) is a potential combustion strategy to achieve high engine efficiency with ultra-low NOx and soot emissions. Fuel stratification can be used to control the heat release rate of RCCI combustion. But the in-cylinder combustion process of the RCCI under different fuel stratification degrees has not been well understood, especially at a higher engine load. In this paper, simultaneous measurement of natural flame luminosity and emission spectra was carried out on a light-duty optical RCCI engine under different fuel stratification degrees. The engine was run at 1200 revolutions per minute under a load about 7 bar indicated mean effective pressure (IMEP). In order to form fuel stratification degrees from low to high, the common-rail injection timing of n-heptane was changed from -180° CA after top dead center (ATDC) to -10° CA ATDC, while the iso-octane delivered in the intake stroke was fixed. The natural luminosity imaging results indicated that, when n-heptane was injected at -180° ATDC, the combustion process looked like HCCI combustion at first with uniform blue flames all over the combustion chamber, but bright soot spots emerged later on. With retarding n-heptane injection timing, combustion regions with higher natural luminosity moved to the edge of the combustion chamber, and the natural flame luminosity got more stratified, showing more signs of soot radiation. The flame emission spectra from RCCI combustion under different fuel stratification degrees showed band spectra of OH, CH, CH2O and C2, as well as continuous spectra of CO oxidation and soot radiation. Band spectra of OH, CH (431.4 nm) and C2 (516.5 nm)/CH2O (422-424 nm and 434.5 nm) became more distinct and appeared successively with the retarding of n-heptane injection timing from -180° ATDC to -10° ATDC.       ]]></description>
      <pubDate>Wed, 28 Jun 2017 14:39:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/1461416</guid>
    </item>
    <item>
      <title>Visual Functions of Older People and Visibility of Traffic Signs</title>
      <link>https://trid.trb.org/View/839535</link>
      <description><![CDATA[This article reports on a study in which two age-related changes of visual functions such as luminous efficiency and visual acuity were investigated in relation to visibility of traffic signs.  The loss of luminous efficiency in the short-wave region (blue lights) and the decrease of visual acuity in nearsight are the predominant changes of visual functions with aging.  The author quantitatively evaluated the visibility change of visual signs associated with these changes.]]></description>
      <pubDate>Wed, 31 Oct 2007 06:39:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/839535</guid>
    </item>
    <item>
      <title>PROPOSED AMERICAN NATIONAL STANDARD PRACTICE FOR ROADWAY LIGHTING</title>
      <link>https://trid.trb.org/View/196131</link>
      <description><![CDATA[This "American National Standard Practice for Roadway Lighting" has been approved under the rules of procedure of the American National Standards Institute and under the sponsorship of the Illuminating Engineering Society of North America (IES).  This document has been revised from the 1977 Standard Practice to include, in addition to an illuminance method for design, a luminance method that incorporates veiling luminance.  Although the luminance method is preferred for most situations, illuminance is regarded as an acceptable alternative.  Design and calculations are now specified in metric units.  Changes in the Appendices (which are not part of the Standard Practice but are provided as supplemental information) include a new Appendix on visibility and one containing metric conversion tables.]]></description>
      <pubDate>Thu, 30 Nov 2000 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/196131</guid>
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