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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
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    <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>
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      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>A complexity perspective on logistics management : rethinking assumptions for the sustainability era</title>
      <link>https://trid.trb.org/View/1663782</link>
      <description><![CDATA[]]></description>
      <pubDate>Mon, 04 Nov 2019 11:17:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/1663782</guid>
    </item>
    <item>
      <title>Dimensionality reduction and identification of valid parameter bounds for the efficient calibration of automated driving functions</title>
      <link>https://trid.trb.org/View/1607073</link>
      <description><![CDATA[The industrialization of automated driving functions according to level 3 requires an efficient test and calibration concept to deal with an increased complexity, growing customer demands, and a larger vehicle fleet offered. Therefore, a method for a complexity reduction of the calibration parameter space is presented. In the two-step approach, a qualitative sensitivity analysis is used to identify valid regions in the search space and subsequently decrease dimensionality based on the parameter-specific global influences. The reduced parameter space and sensitivity information can then serve as a starting point for an efficient calibration process on the target hardware. To examine the method’s potential, the authors' approach is applied to the parameter space of an automated driving function. The results expose clear dependencies between parameters and driving scenarios and allow an exclusion of parameter space dimensions based on sensitivity values. The predefined search space can be narrowed down to valid regions using the parameter range identification approach. Finally, the findings are validated with a quantitative variance-based sensitivity analysis. The validation confirms that the authors' method provides equivalent results with a comparably smaller number of system evaluations.]]></description>
      <pubDate>Tue, 28 May 2019 16:50:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/1607073</guid>
    </item>
    <item>
      <title>Complexity as a Measure of the Difficulty of System Diagnosis in Next Generation Aircraft Health Monitoring System</title>
      <link>https://trid.trb.org/View/1595274</link>
      <description><![CDATA[To develop the Next Generation Aircraft Health Monitoring System (NGAHMS), complexity as a measure of the difficulty of diagnosis, or troubleshooting, of a system is explored in this paper. The results presented can be applied to significantly improve safety and human factor design as an important as aspect of risk engineering and management. This is accomplished in system architecture design by quantifying the system structure’s effect on system complexity as well as the number of components which make up the system. For developing the NGAHMS to make flying even safer, more fuel efficient, and more predictable, model-based safety assessment methods such as Fault Tree Analysis (FTA) and Dependency Diagram (DD) with updated descriptions in SAE ARP4761A and ARP4754B can be used to minimize the average number of airborne inspections to find the Minimal Cut Set (MCS) causing an aircraft failure. Since, based on previous research, this average number of airborne inspections is proven to be lower-bounded by the entropy of cut set importance, the system complexity measure can be used to efficiently estimate how difficult it is to find the actual MCS. This state-of-art safety technique facilitates diagnosing faults effectively, and thus obtain full flight envelope protection for the Next Generation of Air Transport. As a measure for system complexity, this entropy function presents an intrinsic feature of the system, providing the basis of establishing rigorous design principles to diagnose safety-critical faults and thus to cancel their effects systematically through NGAHMS.       ]]></description>
      <pubDate>Wed, 24 Apr 2019 09:30:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/1595274</guid>
    </item>
    <item>
      <title>Modeling the Effect of Task Complexity on Stated Choice Behavior Allowing for Differential Sensitivity: Comparison Between Utility and Regret Models</title>
      <link>https://trid.trb.org/View/1572619</link>
      <description><![CDATA[The aim of this paper is to better understand the effect of task complexity in experimental design on individual choice behavior. Although the scale factor in discrete choice models is generally normalized, studies have consistently pointed out that the imposed randomness on individual choice behavior varies as a function of task complexity. Therefore, several researchers incorporated the effect of task complexity by parameterizing the scale factor as an exponential function of task complexity. Consequently, choice behavior becomes more random with increased task complexity. Moreover, sensitivity to task complexity increases at an exponential rate with decreasing task complexity. In this paper, to relax these rigorous assumptions, the authors propose an alternative function that can be viewed as a generalization of the commonly used exponential function. The newly suggested approach is examined for both conventional utility-maximization and regret-minimization models. To assess the empirical performance of the proposed methodology, they designed a stated preference survey with seven task scenarios, differing in their degree of complexity. Estimation results evidence that the generalized parameterization of the scale factor as a function of task complexity better represents individuals’ stated choices in both utility and regret models.]]></description>
      <pubDate>Fri, 01 Mar 2019 15:51:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/1572619</guid>
    </item>
    <item>
      <title>Exploiting Shadowing Stationarity for Antenna Selection in V2V Communications</title>
      <link>https://trid.trb.org/View/1587070</link>
      <description><![CDATA[Antenna selection (AS) techniques are considered as ideal candidates for vehicle-to-vehicle communications, since they improve system's performance and simultaneously satisfy the hardware and signal processing constraints that exist in these systems. However, the achieved gain over single antenna links is affected by the fast varying wireless channel, since AS is frequently performed using outdated versions of the signal-to-noise ratio (SNR). In this paper, the authors propose an AS technique that exploits the stationarity of large-scale fading. In this context, by employing shadowing information as an AS criterion, the negative consequences of the outdated channel state information (CSI) can be alleviated, since large-scale fading varies more slowly than small-scale fading. The performance of the proposed technique is analyzed using the criteria of outage probability and average output SNR. It is shown that the proposed scheme outperforms the corresponding one that is based on outdated CSI, especially in scenarios with mild fading/shadowing channel conditions. Moreover, the influence of correlated shadowing on the system's performance has been also analytically investigated. The main results have been also verified by empirical data based on measurement campaigns in non-stationary communication conditions.]]></description>
      <pubDate>Thu, 28 Feb 2019 09:39:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/1587070</guid>
    </item>
    <item>
      <title>Toward 5G Wireless Interface Technology: Enabling Nonorthogonal Multiple Access in the Sparse Code Domain</title>
      <link>https://trid.trb.org/View/1569852</link>
      <description><![CDATA[Designers of fifth-generation (5G) wireless networks are focusing on enabling highly reliable low-latency communications that support a high data rate and allow massive connectivity. Nonorthogonal multiple access (NOMA), an essential enabling technology tailored to accommodate a wide range of communication requirements, shows potential as a tool for helping 5G networks to fulfill these promised capabilities. By coordinating connections for massive numbers of devices within the same resource block on power domain, frequency domain, or code domain, NOMA is superior to conventional orthogonal multiple access in terms of network connectivity, system throughputs, and other characteristics. Sparse code multiple access (SCMA) is a kind of multicarrier code-domain NOMA and has been studied extensively. The challenge in designing a high-quality SCMA system is crafting feasible encoding and decoding schemes to meet the desired requirements. In this article, the authors describe recent progress in designing multidimensional codebooks, a practical low-complexity decoder, and grant-free multiple access for SCMA systems. The authors' particular focus is on showing how the designs of the multidimensional constellation and factor graphs (FGs) have formed the foundation of SCMA codebooks. In addition, the authors review various lowcomplexity SCMA decoders with a special emphasis on sphere decoding. Also, they introduce SCMA grant-free transmission based on the framework of belief propagation (BP) and discuss the problem of collision resolution.]]></description>
      <pubDate>Wed, 05 Dec 2018 16:29:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/1569852</guid>
    </item>
    <item>
      <title>Cooperative OFDM-IM Relay Networks With Partial Relay Selection Under Imperfect CSI</title>
      <link>https://trid.trb.org/View/1564272</link>
      <description><![CDATA[In this paper, the authors investigate the performance of cooperative orthogonal frequency division multiplexing with index modulation (OFDM-IM) with the low complexity greedy detection (GD). In particular, the authors propose a novel partial relay selection scheme whose search criteria are designed to exploit the IM subcarriers. To provide low-complexity receiver, the authors further examine the energy-sensing based GD design for the cooperative OFDM-IM. For the performance analysis, the authors derive novel upper bound and approximate closed form solutions for both the average index error probability and the average symbol error probability over Nakagami-m fading channels with imperfect channel state information (CSI) at the relays and destination. Unlike the information theoretical works, in presence of positive detection error in the relays, the derived expressions provide a useful insight into the error performance of cooperative OFDM-IM under various fading conditions. The numerical and simulation results clearly present that the proposed scheme harmonizing partially selected relays and their IM subcarriers with GD can outperform the benchmark schemes, under uncertain CSI, at reduced complexity.]]></description>
      <pubDate>Tue, 20 Nov 2018 10:17:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/1564272</guid>
    </item>
    <item>
      <title>Influence of Task Complexity in Shaping Environmental Review and Engineering Design Durations</title>
      <link>https://trid.trb.org/View/1537302</link>
      <description><![CDATA[Timely completion of environmental reviews for transportation projects has been highlighted as a sore point for performance management by public agencies and industry alike. However, despite its importance, few academic studies investigate project-level performance during the environmental review and engineering design or examine which factors influence it significantly. In this study, the authors observed 560 transportation projects that the Georgia Department of Transportation completed from 2011 to 2015. They modeled distinct processes for three National Environmental Policy Act document types—programmatic categorical exclusion, categorical exclusion, and environmental assessment—and investigated detailed durations for environmental review activities associated with regulatory agency relation management, consultant relation management, and internal project management. Adopting task complexity theories, the authors then examined the influence of four dimensions of task complexity on project performance, measured by the overall durations of the environmental review and engineering design. By investigating performance empirically, this study contributes to methodological advancement and theory development in studies on environmental review. This research contributes to the body of knowledge through the creation of task complexity models to empirically examine the effects of different dimensions of task complexity on environmental review and engineering design durations.]]></description>
      <pubDate>Wed, 31 Oct 2018 09:15:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/1537302</guid>
    </item>
    <item>
      <title>Surrounding traffic complexity analysis for efficient and stable conflict resolution</title>
      <link>https://trid.trb.org/View/1528579</link>
      <description><![CDATA[The constant increase in air traffic demand increases a probability of the separation minima infringements in certain areas as a consequence of increased traffic density. The Annual Safety Report 2016 reports that in recent years the number of infringements, measured per million flight hours, had been increased at a lower rate (Eurocontrol, 2018). However, this level of infringements still generates a continuous pressure on the air traffic control (ATC) system and seeks for more control resources ready to tactically solve potential conflicts, while increasing at the same time the operational costs. Considering present air traffic management (ATM) trade-off criteria: increased airspace capacity and traffic efficiency but reducing the cost while preserving safety, new services must be designed to distribute the separation management ATC task loads among other actors. Based on the Single European Sky Air Traffic Management Research and Next Generation Air Transportation System initiatives, this paper proposes an innovative separation management service to shift the completely centralized tactical ATC interventions to more efficient decentralized tactical operations relying on an advanced surrounding traffic analysis tool, to preserve the safety indicators while considering the operational efficiency. A developed methodology for the proposed service is an application-oriented, trying to respond to characteristics and requirements of the current operational environment. The paper further analysis the traffic complexity taking into consideration the so-called domino effect, i.e. a number of the surrounding aircraft causally involved in the separation management service by the means of identification of the spatiotemporal interdependencies between them and the conflicting aircraft. This complexity is driven by the interdependencies structure and expressed as a time-criticality in quantifying the total number of the system solutions, that varies over time as the aircraft are approaching to each other. The results from two randomly selected ecosystem scenarios, extracted from a simulated traffic, illustrate different avoidance capacities for a given look-ahead time and the system solutions counts, that in discrete moments reach zero value.]]></description>
      <pubDate>Thu, 23 Aug 2018 15:43:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/1528579</guid>
    </item>
    <item>
      <title>A knowledge-transfer-based learning framework for airspace operation complexity evaluation</title>
      <link>https://trid.trb.org/View/1526436</link>
      <description><![CDATA[A sector is a component airspace whose operation is allocated to an air traffic controller. The operation complexity of a sector plays a critical role in the current Air Traffic Management system, e.g. it determines the workload volume of air traffic controllers and serves as a reliable index for airspace configuration and traffic flow management. Therefore, accurately evaluating the sector operation complexity is a problem of paramount importance in both practice and research. Due to numerous interacting factors, traditional methods based on only one single complexity indicator fail to accurately reflect the true complexity, especially when these factors are nonlinearly correlated. In light of these, the attempt to use machine learning models to mine the complex factor-complexity relationship has prevailed recently. The performance of these models however relies heavily on sufficient samples. The high cost of collecting ample data often results in a small training set, adversely impacting on the performance that these machine learning models can achieve. To overcome this problem, this paper for the first time proposes a new sector operation complexity evaluation framework based on knowledge transfer specifically for small-training-sample environment. The proposed framework is able to effectively mine knowledge hidden within the samples of the target sector, i.e. the sector undergoes evaluation, as well as other sectors, i.e. non-target sectors. Moreover, the framework can properly handle the integration between the knowledge derived from different sectors. Extensive experiments on real data of 6 sectors in China illustrate that the authors' proposed framework can achieve promising performance on complexity evaluation when only a small training set of the target sector is available.]]></description>
      <pubDate>Thu, 16 Aug 2018 09:44:34 GMT</pubDate>
      <guid>https://trid.trb.org/View/1526436</guid>
    </item>
    <item>
      <title>A Decision Support Framework for Assessing the Contextual Factors for Complex Highway Projects</title>
      <link>https://trid.trb.org/View/1494619</link>
      <description><![CDATA[Traditional strategies for highway projects during the 1950s and 1960s focused on three dimensions of project management: cost, schedule, and technical (scope). Recently, with the focus shifting towards reconstruction/rehabilitation projects, project management strategies have shifted to include other project management dimensions. The Second Strategic Highway Research Program (SHRP2) project R-10 examined the best practices for managing complex renewal projects. The primary outcome of the study was a recommendation to utilize a five-dimensional project management planning (5DPM) model that added context and financing as two new dimensions to the traditional dimensions of cost, schedule, and technical. Pilot testing of the 5DPM implementation suggested that the most complicated dimension to assess during the project management planning phase for a complex project is the context dimension. Currently there is no efficient, structured process for evaluating the context dimension on complex projects within the 5DPM framework. Given this, the objective of this study is to develop a decision support framework which can be used by different transportation agencies when assessing contextual factors and assigning complexity rating scores. The framework uses a structured analytical process as opposed to the more subjective scoring used during the 5DPM workshops. As a major part of its methodology, this research uses a multiple-criteria decision-making tool called analytical hierarchy process in developing the framework. The paper presents two implementation examples which demonstrate the feasibility of the developed framework for a rebuild project and an expansion project.]]></description>
      <pubDate>Tue, 27 Mar 2018 11:15:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/1494619</guid>
    </item>
    <item>
      <title>Symbol Cyclic Shift Equalization PAM-OFDM—A Low Complexity CP-Free OFDM Scheme</title>
      <link>https://trid.trb.org/View/1475286</link>
      <description><![CDATA[In traditional orthogonal frequency division multiplexing (OFDM) systems, a cyclic prefix (CP) must be used in every block for intersymbol interference (ISI) suppression in time-dispersive channels at a price of severely impaired spectrum efficiency. To deal with this issue, the symbol cyclic shift equalization (SCSE) algorithm was proposed to implement a CP-free OFDM system. In this paper, the authors aim to further reduce the computational complexity of the SCSE algorithm. In particular, a pulse amplitude modulation (PAM) is used at a transmitter to construct conjugate symmetric OFDM blocks, while only partial samples in an OFDM block are involved in the SCSE algorithm at the receiver side, leading to a significantly reduced implementation complexity if compared to an SCSE quadratic-amplitude modulation(QAM)/phase-shift keying (PSK)-OFDM system, where all samples in an OFDM block must be involved in the detection process. The performance of the proposed SCSE PAM-OFDM scheme is analyzed and compared to traditional OFDM systems. The results obtained from this paper verify the effectiveness of the proposed scheme.]]></description>
      <pubDate>Fri, 22 Sep 2017 16:45:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/1475286</guid>
    </item>
    <item>
      <title>Antenna Selection in RF-Chain-Limited MIMO Interference Networks Under Interference Alignment</title>
      <link>https://trid.trb.org/View/1467397</link>
      <description><![CDATA[In multiple-input multiple-output (MIMO) systems, the deployment of multiple radio-frequency (RF) chains is much more expensive than that of multiple antennas. Antenna selection (AS) is a low-cost low-complexity method to exploit the diversity gain in MIMO systems with sufficient antennas but limited RF chains. Among the AS algorithms, decremental AS has been shown to be near-optimal compared with exhaustive search. In this paper, the authors study AS in MIMO interference networks applying the interference alignment (IA) scheme. IA aligns and zero-forces the interference via transmitter–receiver beamforming and achieves a maximum degree of freedom. The feasibility and alignment topology of IA is dependent on the active antenna configuration. For users in tightly feasible systems, IA can be resumed after AS by adapting the beamformers locally, and the exact transmission rate can be known. For users in superfeasible systems, the authors derive the expected rate under IA conditioned on local channel state information (CSI). Adopting the rate or expected rate as selection criterion, the authors propose the decremental AS algorithms achieving a twofold complexity reduction. Simulation results and complexity analysis show that the algorithms achieve near-optimal performance at low complexity.]]></description>
      <pubDate>Fri, 23 Jun 2017 11:40:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/1467397</guid>
    </item>
    <item>
      <title>Factors Influencing Visual Search in Complex Driving Environments</title>
      <link>https://trid.trb.org/View/1467515</link>
      <description><![CDATA[The objective of this study was to describe and model the effects of varied roadway environment factors on drivers’ perceived complexity, with the goal of further understanding conditions for optimal driver behavior and performance. This was investigated by obtaining self-reported ratings of complexity from several participant populations across an array of static and dynamic roadway environments. Descriptive and predictive models of perceived complexity were developed for varied driver demographic groups and roadway environment types. Environmental conditions, urban arterial environments, and the presence of roadside restrictions were seen to significantly increase perceived complexity of static roadway environments; and drivers with fewer than 12 months following licensure tended to rate environments as less complex than drivers with more experience. Results from the dynamic roadway environments experiment indicated that traffic had the greatest effect on perceived complexity; and work zones with lower path guidance (drums) interacted with lane configuration and roadside objects to have increased effects on perceived complexity. Understanding the effects of roadway factors on drivers’ perceived complexity could inform enhanced roadway design and guidance for all transportation system users, guide road safety audits, and provide a foundation for factors that should be examined in future research studies.]]></description>
      <pubDate>Mon, 05 Jun 2017 11:45:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/1467515</guid>
    </item>
    <item>
      <title>Pattern Division Multiple Access—A Novel Nonorthogonal Multiple Access for Fifth-Generation Radio Networks</title>
      <link>https://trid.trb.org/View/1465613</link>
      <description><![CDATA[In this paper, pattern division multiple access (PDMA), which is a novel nonorthogonal multiple access scheme, is proposed for fifth-generation (5G) radio networks. The PDMA pattern defines the mapping of transmitted data to a resource group that can consist of time, frequency, and spatial resources or any combination of these resources. The pattern is introduced to differentiate signals of users sharing the same resources, and the pattern is designed with disparate diversity order and sparsity so that PDMA can take the advantage of the joint design of transmitter and receiver to improve system performance while maintaining detection complexity to a reasonable level. System level simulation results show that PDMA can support six times simultaneous connections than that of conventional and at least 30% improvement in spectrum efficiency over orthogonal frequency division multiple access.]]></description>
      <pubDate>Fri, 02 Jun 2017 12:49:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/1465613</guid>
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