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    <title>Transport Research International Documentation (TRID)</title>
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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>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Numerical Study with Field Data for Macroscopic Continuum Modelling of Indian Traffic</title>
      <link>https://trid.trb.org/View/1644766</link>
      <description><![CDATA[Heterogeneous traffic as observed in several south Asian countries is characterized by complex interactions of widely varying vehicle types that do not follow lanes and with smaller vehicles filling any gaps available. This paper discusses on four main components of macroscopic simulation of traffic flow in the Indian traffic context. One of the prime component, namely the traffic flow model, is discussed in detail with respect to the continuum modelling approach.]]></description>
      <pubDate>Thu, 19 Sep 2019 15:07:34 GMT</pubDate>
      <guid>https://trid.trb.org/View/1644766</guid>
    </item>
    <item>
      <title>Assessment of post-disaster reentry traffic in megaregions using agent-based simulation</title>
      <link>https://trid.trb.org/View/1639599</link>
      <description><![CDATA[Transportation personnel, assets, and systems play important roles during emergencies. Of particular note is the critical function of road networks as lifelines for evacuations, then, after such events, to facilitate the rapid inflow of support personnel and resources needed to assess and repair damage. They also provide access for the safe and rapid return of evacuees. Despite the importance of reentry and repopulation, the role of transportation systems for them has been a relatively lightly researched topic. This paper describes research to analyze the traffic processes associated with post-evacuation reentry and its associated travel time and delay. To examine the most extreme of conditions; this effort also focused on repopulation and reentry after mass evacuations in megaregions. Among the findings of this work were that, as expected, reentry traffic processes generally behave similar to, but in the reverse direction, of evacuations. However, contrary to commonly held belief, they are not identically opposite. Rather, network performance during reentry may often be better than that of evacuation. Another broad finding of the research was that the spatial heterogeneity of traffic distribution across available roadways is a primary factor in determining network performance, meaning the more uniform the spread of on all links, the more efficient the network will operate. A third significant finding of this research was also the importance of the temporal spreading of returnee departure times on network efficiency.]]></description>
      <pubDate>Wed, 07 Aug 2019 09:19:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/1639599</guid>
    </item>
    <item>
      <title>Determinants of time headway in staggered car-following conditions</title>
      <link>https://trid.trb.org/View/1637745</link>
      <description><![CDATA[Precise understanding of the factors affecting the choice of following time headway in staggered car-following conditions is essential  on the part of traffic  modelers to provide a detailed representation of traffic flow, which has a predominant role in microsimulation model development, safety evaluation, capacity estimation and evaluation of traffic management strategies. Using trajectory data from video recordings, an evaluation of the impact of a number of factors (i.e. road width,  centerline separation, lead vehicle type) on the following headway of a driver is undertaken in this study. A seemingly unrelated regression (SUR) model for time headways is also developed to examine the correlation of headways with different determinants and speeds of following vehicles. Results of the study suggest that though there is a direct relationship between speed and headway, the extent of off-centeredness between the interacting pair and vehicle type-specific interactions need to be considered to develop mixed-traffic microsimulation models.]]></description>
      <pubDate>Wed, 24 Jul 2019 09:35:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1637745</guid>
    </item>
    <item>
      <title>H-CTM for simulating non-lane-based heterogeneous traffic</title>
      <link>https://trid.trb.org/View/1632685</link>
      <description><![CDATA[This paper developed a first-order deterministic macroscopic model H-CTM (heterogeneous cell transmission model) based on basic cell transmission model (CTM). The methodological calibration of the model considers the aggregate behavior of heterogeneous traffic under weak lane discipline. H-CTM incorporates a nonlinear fundamental diagram (FD), modeled for non-lane-based heterogeneous traffic, instead of traditional piecewise linear FD. For validating the model performance, high resolution traffic data were collected from a major arterial roadway (N3-Highway) of Dhaka city covering both peak and off-peak periods. Subsequently, the calibrated FD parameters were incorporated in the newly developed H-CTM to simulate the traffic. The estimated traffic states by the proposed model were then compared with basic model of CTM. Model performances, calculated in terms of mean absolute error based on ground truth values show that the H-CTM can be used to describe the traffic dynamics in the stated traffic system better than the basic model.]]></description>
      <pubDate>Fri, 12 Jul 2019 16:58:38 GMT</pubDate>
      <guid>https://trid.trb.org/View/1632685</guid>
    </item>
    <item>
      <title>Modeling of lateral gap maintaining behavior of vehicles in heterogeneous traffic stream</title>
      <link>https://trid.trb.org/View/1632684</link>
      <description><![CDATA[Vehicular movement in heterogeneous traffic stream with no-lane-disciplined is not only influenced by the characteristics of the leading vehicle but also by the presence of the adjacent vehicles. In such scenario, lateral gap maintaining behavior plays a significant role in the vehicular movement. Field data analyses show that there is a wide variation in the total lateral gaps, even for a particular combination of passing/overtaking vehicle and both the adjacent vehicles. Speed and type of the passing/overtaking vehicle and the speed and type of both the adjacent vehicles were found to be having a significant influence on the total lateral gaps. The variability in the critical total lateral gaps has been explained using the variables such as the speed and type of the subject vehicle, as well as the adjacent vehicles. Developed models were found to be statistically significant in replicating the field observed total lateral gaps corresponding to various types of vehicles. The impact of different lateral gap models has been studied using a CA-based simulation model and found that the gap maintaining behavior significantly influences the flows close to capacity.]]></description>
      <pubDate>Fri, 12 Jul 2019 16:58:38 GMT</pubDate>
      <guid>https://trid.trb.org/View/1632684</guid>
    </item>
    <item>
      <title>Preferred time headway of drivers on two-lane highways with heterogeneous traffic</title>
      <link>https://trid.trb.org/View/1593661</link>
      <description><![CDATA[This paper presents an investigation on the adequacy of one of the major performance indicators for two-lane highways, the percent-time-spent-following (PTSF) under changing driver’s behavior in choosing headways. Field study was conducted on a two-lane highway in India that exhibits heterogeneity in its traffic composition and a wide range of flow levels was covered while collecting data. The appropriate headway distributions were selected based on goodness-of-fit test. Exponential or Erlang distributions exhibit their aptness in describing headways up to a volume to capacity ratio of 0.3 and gamma and exponential distributions were compatible for headway data corresponding to a volume to capacity ratio of 0.4 and above. Around 40% drivers were observed to adopt headways 2 s or less at heavy flow when a car-following situation prevails; these headways are considered unsafe in several instances. Further, speed–headway relationships were established to assess a headway threshold beyond which vehicles could be considered free. Empirical investigation indicates a value of about 6 s under such traffic unlike 3 s as considered in PTSF estimation. Another major implication on PTSF is a few drivers move in a platoon by choice even if they have a gap of more than 6 s and passing opportunities.]]></description>
      <pubDate>Fri, 29 Mar 2019 10:15:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/1593661</guid>
    </item>
    <item>
      <title>Resilient Mixed Integer Linear Programming Formulation for Heterogeneous Traffic Signal Priority Scheduling Problem</title>
      <link>https://trid.trb.org/View/1573359</link>
      <description><![CDATA[Traffic signal priority (TSP) is a common operation at signalized intersections to accommodate the green requests from special vehicles like buses or ambulance as well as emerging connected automated vehicles (CAV). The special vehicles requiring the TSP service can be classified into two categories: high-priority special vehicles such as fire trucks, ambulances or trains and low-priority special vehicles like buses or trams, etc. The high-priority TSP requests are hardly deniable because the incurred delay otherwise may result in loss of lives or fatal crashes whereas the low-priority TSP requests can be declined or postponed if certain conditions cannot be met. While most TSP strategies today allow for placing the TSP requests only 20 to 30 seconds away, special vehicles or CAVs can transmit TSP requests via mobile computing technique minutes before they arrive at the downstream intersections. This new feature offers additional flexibilities in the TSP scheduling problem. In this paper, the authors present a resilient optimization framework for heterogeneous TSP scheduling based on a recently developed phase-time network model. The heterogeneous priorities of TSP requests is interpreted as various lengths of TSP time windows in the phase-time network. As a result, scheduling heterogeneous TSP requests over time is viewed as a vehicle routing problem with pickup time windows (VRPTW). Unlike most ad-hoc green-extension or red-truncation-based TSP strategies, this new method will not break the existing traffic signal control configuration and therefore will minimize the negative impact on the mobility of background traffic. Two mathematical programming formulations are developed: (i) Mixed Integer Linear Programming (MILP) formulation and resilient MILP formulation (R-MILP). The R-MILP formulation is modified from the basic phase-time work model in such a way that the mathematical solver can always reach a mathematically feasible solution but the solution is not necessarily feasible in the real world. This features enable the authors to identify those infeasible conditions for the TSP scheduling. Four numerical experiments are conducted to validate and examine the robustness of the proposed approach.]]></description>
      <pubDate>Fri, 01 Mar 2019 15:51:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/1573359</guid>
    </item>
    <item>
      <title>Traffic flow estimation at error prone locations using dynamic traffic flow modeling</title>
      <link>https://trid.trb.org/View/1566595</link>
      <description><![CDATA[Macroscopic model-based schemes are appropriate for real-time estimation of traffic density, which is an important congestion indicator. Conservation of vehicles equation is one of the basic equations used in any macroscopic model-based analysis. However, to apply the conservation equation, accurate flow/count data should be available, which can be achieved only if suitable traffic sensors are available. In reality, automated traffic sensors are prone to measurement errors, especially under heterogeneous, less lane-disciplined and congested traffic conditions. Use of this erroneous data can lead to wrong estimation of traffic variables. This study proposes a lumped parameter macroscopic model-based scheme for the estimation of flow at error-prone locations. The estimation scheme was designed based on the extended Kalman filter. The performance of the proposed scheme was evaluated for density estimation by comparing the results using accurate flow data collected manually, using automated sensor data and flow estimated using the proposed methodology. The results showed that with the proposed scheme, average error in estimated density for the sections under consideration was around 20.8%, whereas it was found to be 30% with direct use of automated sensor data. This shows that at error prone locations, the proposed model is a viable alternative to the direct use of erroneous automated data.]]></description>
      <pubDate>Tue, 20 Nov 2018 10:11:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/1566595</guid>
    </item>
    <item>
      <title>Effect of traffic composition and emergency lane on capacity: a case study of intercity expressway in India</title>
      <link>https://trid.trb.org/View/1540994</link>
      <description><![CDATA[The study is intended to investigate the effect of traffic composition and the use of a paved emergency lane on capacity. Ahmedabad–Vadodara four-lane divided intercity expressway (Mahatma Gandhi expressway, designated as NE-1) which has an emergency lane on either side is taken as a case study. For modeling traffic flow on expressway, a microscopic simulation technique is employed in this study. The simulation model was developed, calibrated, and validated for rendering as well as replicating the real traffic conditions. Results of the study show that the capacity is greatly influenced by emergency lanes and traffic composition. The result of the present study is expected to highlight the ongoing national-level efforts of developing guidelines for Indo-Highway Capacity Manual.]]></description>
      <pubDate>Thu, 27 Sep 2018 16:10:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/1540994</guid>
    </item>
    <item>
      <title>Passenger Car Equivalents for the Heterogeneous Traffic on Divided Rural Highways Based on Simulation Model</title>
      <link>https://trid.trb.org/View/1532735</link>
      <description><![CDATA[Passenger car equivalent (PCE) values are necessary for representing a traffic stream composing of different vehicle types in terms of a passenger car equivalent stream. For no lane-based heterogeneous traffic streams observed in India, previous studies mostly have suggested the vehicle-specific PCE values that vary dynamically with the flow rate and the traffic composition. The objective of this paper is to estimate and analyze the implications of the vehicle-specific PCE values that do not vary with the LOS and certain range of traffic composition, for the four-lane and the six-lane divided rural roads. Besides, the present study has also estimated the aggregate PCEs for the four-lane and the six-lane divided roads. The PCE values were estimated based on the macroscopic relationships generated for the base and the heterogeneous traffic streams. For defining the level of service, a new performance measure termed as the speed drop was chosen and it was found that it provides a relatively more accurate PCEs. Results show that for a particular traffic mix, constant PCEs can be used across different levels of service without much loss of accuracy. Aggregate PCEs for a particular traffic mix vary with the speed drop markedly at lower flow rates.]]></description>
      <pubDate>Mon, 17 Sep 2018 10:32:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/1532735</guid>
    </item>
    <item>
      <title>Effect of the car-following combinations on the instability of heterogeneous traffic flow</title>
      <link>https://trid.trb.org/View/1509270</link>
      <description><![CDATA[Heterogeneous traffic flow contains the mixed operation of the different vehicle classes such as cars, trucks and buses. Previous study has indicated that the overall stability of the heterogeneous traffic flow is governed by a weighted mean of stability parameters corresponding to each vehicle class and is not affected by the order in which a vehicle class is put into the system, for example either car or truck. However, it has been recently reported that the effect of mixed composition on traffic flow dynamics is also determined by the car-following vehicle type, that is either car following a car or car following a truck. This paper aims at investigating analytically how different car-following combinations (i.e. the following type) influence the overall stability of heterogeneous traffic flow dynamics. More specifically, the authors will consider the four types of car-following behaviour such as car–car, car–truck, truck–car, and truck–truck. The effect of such car-following types on the overall linear stability condition of the heterogeneous traffic flow will be studied using a generalised multi-class car-following model in which the optimal speed function is not only dependent on the the space headway between two consecutive vehicles as in previous study of Mason and Woods [1997. “Car-following Model of Multispecies Systems of Road Traffic.” Physical Review E: 2203–2214] but also on the and the relative speed between those two consecutive vehicles.]]></description>
      <pubDate>Thu, 17 May 2018 14:46:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/1509270</guid>
    </item>
    <item>
      <title>A vehicle type-dependent visual imaging model for analysing the heterogeneous car-following dynamics</title>
      <link>https://trid.trb.org/View/1509282</link>
      <description><![CDATA[Heterogeneity is an essential characteristic in car-following behaviours, which can be defined as the differences between the car-following behaviours of driver/vehicle combination under comparable conditions. This paper proposes a visual imaging model (VIM) with relaxed assumption on (1) a driver's perfect perception for the states of the neighbouring vehicles (e.g. spacing, velocity, etc.) and (2) uniform reaction to vehicles with different sizes in most existing car-following models. VIM utilises the visual imaging information subtended by the preceding vehicle as the stimuli drivers react to, and can generate greater stimuli from the preceding vehicle with larger apparent size (i.e. vehicle width × vehicle height) under short gap distance with the follower, but less change in stimuli from the distant leading vehicle under various apparent sizes. The NGSIM data containing vehicle type/size information is used to evaluate VIM at different levels. At the level of single trajectory pair, the calibrated VIM occupies the well capability of reproducing the trajectory of the follower, and can also reproduce statistical results from the field data, that is, the gap distance for car-following truck (C-T) is greater than that for car-following car (C-C). At the level of vehicle type, the calibration results also show the promising performance of VIM in describing heterogeneous car-following behaviours with the simple model formulation and limited model parameters compared with other six reference models.]]></description>
      <pubDate>Thu, 17 May 2018 14:46:08 GMT</pubDate>
      <guid>https://trid.trb.org/View/1509282</guid>
    </item>
    <item>
      <title>Investigation of Information Quality and User Response to Real-Time Traffic Information Under Heterogeneous Traffic Conditions</title>
      <link>https://trid.trb.org/View/1509162</link>
      <description><![CDATA[Advanced Traveler Information Systems (ATIS) are extensively employed to tackle the increasing traffic congestion problems. The success of ATIS depends on their ability to influence the user responses in the desired direction. Due to the limited implementations in India and lack of systematic and rigorous studies on user response to real-time traffic information from ATIS, the impact of ATIS in mixed traffic are not well understood. This study aims to bridge some of these gaps. The objectives of this study are: (1) to investigate the user response to ATIS under heterogeneous traffic conditions, and (2) to evaluate the quality of information provided through different ATIS. The study focuses on the impacts of a prototypical ATIS project which provides dynamic traffic information on a study corridor in Chennai. The information is provided to the user through a web portal and Variable Message Sign boards (VMS) at six locations on the study corridor. While the VMS provides travel time information on alternate routes, the web-based information includes travel times and alternate routes, congestion maps, speed and delay maps, and live traffic images. A survey of users’ actual response to traveler information revealed that the users’ experience and attitude towards ATIS are favorable and positive. Users perceived the information as accurate and majority were satisfied with the information provided. The findings from this study establishes the necessity of an ATIS evaluation scheme specific to heterogeneous traffic conditions.]]></description>
      <pubDate>Thu, 17 May 2018 14:45:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/1509162</guid>
    </item>
    <item>
      <title>Estimation of PCE values for hill roads in heterogeneous traffic conditions</title>
      <link>https://trid.trb.org/View/1507924</link>
      <description><![CDATA[The traffic operations of hill roads are an important aspect that needs to be understood. In order to ascertain the traffic performance, estimating the passenger car equivalent (PCE) values and capacities are critical. PCE values are dynamic and vary with small change in any of the influencing characteristics. These values and roadway capacities vary with the estimation method adopted in the analysis. This study aims to understand the influencing factors for estimation and eventually estimating the PCE values of different vehicle types on hill roads. This study includes a review of various methods for estimating PCEs followed by data collection on hill roads of the northeastern state of India (Meghalaya state). PCE values are estimated based on the three important methods identified. These are, (i) Speed-area method, (ii) modified density method, and (iii) area occupancy method. For the data sets analyzed under the prevailing traffic mix, the volumes were very low and the vehicles are predominantly cars, SUVs and trucks with negligible proportion of two wheelers. PCE values obtained from speed-area method are on the higher side for heavy vehicles and on lower side for motorized two wheelers compared with the modified density method and area occupancy methods. Modified density method and area occupancy methods show different PCE values yet these two methods confirm that in hilly terrains having low level of traffic volume, range of PCE values for heavy vehicles and motorized two wheelers decreases by a considerable extent.]]></description>
      <pubDate>Thu, 26 Apr 2018 09:13:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/1507924</guid>
    </item>
    <item>
      <title>Development of Safety Performance Functions: Incorporating Unobserved Heterogeneity and Functional Form Analysis</title>
      <link>https://trid.trb.org/View/1493027</link>
      <description><![CDATA[To improve transportation safety, this study applies Highway Safety Manual (HSM) procedures to roadways while accounting for unobserved heterogeneity and exploring alternative functional forms for Safety Performance Functions (SPFs). Specifically, several functional forms are considered in Poisson and Poisson-gamma modeling frameworks. Using 5 years (2011–2015) of crash, traffic, and road inventory data for two-way, two-lane roads in Tennessee, fixed- and random-parameter count data models are calibrated. The models account for important methodological concerns of unobserved heterogeneity and omitted variable bias. With a validation dataset, the calibrated and uncalibrated HSM SPFs and eight new Tennessee-specific SPFs are compared for prediction accuracy. The results show that the statewide calibration factor is 2.48, suggesting rural two-lane, two-way road segment crashes are at least 1.48 times greater than what HSM SPF predicts. Significant variation in four different regions in Tennessee is observed with calibration factors ranging between 2.02 and 2.77. Among all the SPFs considered, fully specified Tennessee-specific random parameter Poisson SPF outperformed all competing SPFs in predicting out-of-sample crashes on these road segments. The best-fit random parameter SPF specification for crash frequency includes the following variables: annual average daily traffic, segment length, shoulder width, lane width, speed limit, and the presence of passing lanes. Significant heterogeneity is observed in the effects of traffic exposure-related variables on crash frequency. The study shows how heterogeneity-based models can be specified and used by practitioners for obtaining accurate crash predictions.]]></description>
      <pubDate>Thu, 12 Apr 2018 13:38:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/1493027</guid>
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