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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>
    <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>A HIGH-FLOW TRAFFIC-COUNTING DISTRIBUTION</title>
      <link>https://trid.trb.org/View/117046</link>
      <description><![CDATA[ALTHOUGH MANY OBSERVATIONS HAVE BEEN MADE ON INTERVEHICLE HEADWAYS AND TRAFFIC VOLUMES, IT IS IMPORTANT TO IMPROVE THE THEORETICAL BASES FOR PREDICTING A NUMBER OF FLOW AND DENSITY CHARACTERISTICS FROM A LIMITED NUMBER OF OBSERVATIONS. WHEREAS CONSIDERABLE ATTENTION HAS BEEN GIVEN TO THE THEORETICAL AND EXPERIMENTAL EVALUATION OF THE STATISTICAL DISTRIBUTIONS OF INTERVEHICLE SPACINGS, THERE HAS BEEN MUCH LESS INFORMATION AVAILABLE ABOUT THE DISCRETE COUNTING DISTRIBUTIONS. THE PRINCIPAL EFFORT HAS BEEN DEVOTED TO POISSON-LIKE COUNTING DISTRIBUTIONS. THE PURPOSE OF THIS PAPER IS TO REVIEW AND PRESENT COUNTING DISTRIBUTIONS WHICH TAKE INTO ACCOUNT TWO FUNDAMENTAL CHARACTERISTICS OF MEDIUM-AND HIGH-DENSITY TRAFFIC FLOWS: (1) PLATOONING OR BUNCHING, AND (2) MINIMUM SPACING, JAM- DENSITY OF THE SO-CALLED MAXIMUM-PACK SITUATIONS. THESE COUNTING DISTRIBUTIONS ARE DERIVED FROM INTERVEHICLE SPACING DISTRIBUTIONS, WHICH HAVE BEEN STUDIED BOTH THEORETICALLY AND EXPERIMENTALLY. IN THE LOW-DENSITY OR LOW-FLOW CASE IT IS SHOWN THAT THESE DISTRIBUTIONS HAVE THE LIMITS OF THE WELL-KNOWN POISSON CASE. /AUTHOR/]]></description>
      <pubDate>Fri, 13 Aug 2004 18:56:02 GMT</pubDate>
      <guid>https://trid.trb.org/View/117046</guid>
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    <item>
      <title>MICROSCOPIC MODELING OF TRAFFIC WITHIN FREEWAY LANES</title>
      <link>https://trid.trb.org/View/453103</link>
      <description><![CDATA[Microscopic models provide an understanding of traffic operations at the level of passage of individual vehicles. Roadway performance can be ascertained by understanding how vehicles interact with each other.  Cowan's M3 headway distribution models were calibrated for the curb and median lanes of two-lane mainline freeway segments, using data captured at 14 sites.  Calibration of the relationship among Cowan's M3 parameters, proportion of headways greater than a minimum of 1 sec, and flow rate yielded exponential decay equations for each lane.  The M3 models provide a source of vehicle arrivals for gap acceptance models, which may be used to quantify the ability of drivers to change lanes, for example.  It was found that the parameters calibrated for each lane are suitable for use at any mainline site, independent of site-specific conditions.  The proportion of small headways was found to be higher in the median lane than the curb, for all flow rates, and for both lanes lower than their respective equivalents on arterial roads with intersections.  The largest bunched headway was considered to be between 2 and 3 sec.  The models predicted bunching between 85% and 93% of median lane vehicles, and between 75% and 90% of curb lane vehicles, at capacity.  The lesser amount of curb lane bunching reflects its use as a slower vehicle lane with greater stream friction.]]></description>
      <pubDate>Fri, 19 Jan 1996 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/453103</guid>
    </item>
    <item>
      <title>PROBABILISTIC MODELS OF PASSENGERS SERVICE PROCESSES AT BUS STOPS</title>
      <link>https://trid.trb.org/View/371217</link>
      <description><![CDATA[Stop time variability in bus operation is known to be very often the dominant factor which influences bunching. The aim of this paper is to study in detail the main stochastic factors which affect the times spent by buses at stops. For this purpose various realistic random representations for main determinants of the parallel and series passengers service processes at bus stops are chosen. New analytical expressions for density functions and moments of the stop time random variable are derived. The results have been tested on data from a real bus route.]]></description>
      <pubDate>Wed, 27 Oct 1993 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/371217</guid>
    </item>
    <item>
      <title>THE CONSUL DISTRIBUTION AS A BUNCHING MODEL IN TRAFFIC FLOW</title>
      <link>https://trid.trb.org/View/359914</link>
      <description><![CDATA[The Consul distribution introduced by Consul and Shenton (1975), and modified by Islam and Consul (1990) is derived as a bunching model in traffic flow through the branching process and also through the birth-and-death process. Some applications of the model to vehicle bunch size data are also considered.]]></description>
      <pubDate>Sat, 30 Nov 1991 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/359914</guid>
    </item>
    <item>
      <title>DESIGN GUIDELINES FOR OVERTAKING LANES</title>
      <link>https://trid.trb.org/View/276580</link>
      <description><![CDATA[An overtaking lane is an auxiliary lane provided on a two-lane highway to enhance overtaking opportunities. Overtaking lanes offer a low-cost alternative to major reconstruction of two-lane roads or four-lane divided standards.  They are used by road authorities as an intermediate level of road improvement on roads which do not meet warrants for four-laning, but exhibit deteriorating level of service in terms of reduced speeds, increased time spent following in platoons, and a demand for overtaking which exceeds the available opportunities.  Although overtaking lane design guidelines have evolved independently in Canada and Australia there are a number of common elements.  These include:  advance notification of the overtaking lane; a keep left unless overtaking sign at the diverge point; advance notification of the merge and signs at the merge; and some indication for traffic in the opposing lane that they are facing an overtaking lane. There is general agreement that the provision of short overtaking lanes at regular spacing is more cost-effective than the provision of a few long ones, but Australian recommended lengths are shorter than those in Canada. Overly-restrictive barrier lines for the opposing lane, especially on low-volume roads where sight distance is adequate, can be counterproductive by causing platooning and driver frustration.  Bunching is suggested as the level of service measure best suited for determining the need for and evaluation of overtaking lanes.  Research needs for overtaking lanes are highlighted.  (Author/TRRL)]]></description>
      <pubDate>Wed, 31 Oct 1990 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/276580</guid>
    </item>
    <item>
      <title>USE OF TRAFFIC SIMULATION TO EVALUATE RURAL ROAD IMPROVEMENT ALTERNATIVES</title>
      <link>https://trid.trb.org/View/290136</link>
      <description><![CDATA[This paper describes a rural traffic simulation model called trarr version 3.0 developed at the Australian road research board.  The model can be used to simulate the traffic operations on a real road in some detail, and to investigate the effects of changes in road and traffic characteristics. By changing the road geometry characteristics, alternative road improvement strategies may be compared.  By changing the traffic characteristics, the user can investigate the effects of increased volumes, more heavy trucks, or long-term changes in vehicle size and power.  Observed traffic characteristics include speed, travel time, bunching, time spent following, overtaking rate and fuel consumption.  (TRRL)]]></description>
      <pubDate>Tue, 31 Jan 1989 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/290136</guid>
    </item>
    <item>
      <title>BUNCHING THEORY APPLIED TO MINIMIZE COST</title>
      <link>https://trid.trb.org/View/284156</link>
      <description><![CDATA[Bunching (Queue's) theory is developed into a quickly applicable set of curves.  When these curves are realistically applied, they assure the most economical match-up of hauler fleet size per loader.]]></description>
      <pubDate>Mon, 31 Aug 1987 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/284156</guid>
    </item>
    <item>
      <title>A MODEL FOR SIMULATING TRAFFIC ON TWO-LANE RURAL ROADS: USER GUIDE AND MANUAL FOR TRARR VERSION 3.0</title>
      <link>https://trid.trb.org/View/267316</link>
      <description><![CDATA[TRARR is a rural traffic simulation model developed at the Australian Road Research Board.  The model can be used to investigate the effects on traffic operations of changes in either the road or traffic characteristics.  TRARR has been used at ARRB on specific case studies requested by road authorities, and in general investigations of level of service and guidelines for rural road improvements.  The model has also been provided to numerous organisations outside ARRB, many of them outside Australia.  A new version, TRARR 3.0, has recently been released, with improved transportability and simplified user requirements. TRARR requires input data on the traffic stream, road characteristics, and what is to be observed and recorded. It then reviews the progress of each vehicle at frequent intervals as it moves along the simulated road.  Decision rules for catching up, overtaking, merging and other aspects of behaviour are largely determined by the vehicle/driver characteristics supplied in one of the input files.  Many of these parameters have been derived from other ARRB research projects.  Outputs include travel time, journey speed, bunching, overtaking and fuel consumption information, as well as plots and terminal graphics display.  (Author/TRRL)]]></description>
      <pubDate>Sat, 31 May 1986 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/267316</guid>
    </item>
    <item>
      <title>SIMULATION STUDY OF GUIDELINES FOR RURAL ROAD IMPROVEMENTS</title>
      <link>https://trid.trb.org/View/217811</link>
      <description><![CDATA[The rural traffic simulation model TRARR was used to evaluate a range of options for improving traffic performance on two-lane rural roads in Australia. The options include auxiliary lanes, widening to four lanes, and reconstruction on an improved alignment. Simulated travel times, bunching rates, and overtaking rates are presented for these options for a range of terrains and traffic volumes. Benefit-cost analysis was used to derive a volume warrant for each option, based on construction costs and reductions in travel times and accidents. Minimum volume warrants of 385 to 6,800 vehicles per day were found, depending on the terrain, the existing road standard, and the type of road improvement considered. Practical warrants are likely to be higher than these minimum values, but the relative rankings appear to be robust.]]></description>
      <pubDate>Fri, 31 Jan 1986 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/217811</guid>
    </item>
    <item>
      <title>RECENT DEVELOPMENTS IN RURAL ROAD DESIGN</title>
      <link>https://trid.trb.org/View/216777</link>
      <description><![CDATA[Rural road design practice in Australia has undergone a number of changes in recent years, and this process of change is continuing.  Greater emphasis is now being placed on the cost-effectiveness of road design elements, and matching road improvement proposals to the objectives of a particular project.  This paper discusses a number of developments in geometric road design, with particular reference to the contributions made by the Australian Road Research Board, and the continuing research in this area. Some of the major changes are the greater emphasis on alignment consistency, the growing use of auxiliary lanes and the move towards partial sealing of shoulders.  Greater attention is also being paid to provision for out-of- control vehicles, especially on steep downgrades.  Traffic simulation has been used to evaluate alternative road improvement strategies, and to develop new measures of level of service based on traffic bunching.  A consideration of accidents and road geometry is an underlying theme of the research on all of these topics.  (Author/TRRL)]]></description>
      <pubDate>Sat, 31 Aug 1985 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/216777</guid>
    </item>
    <item>
      <title>TRAFFIC FLOW THEORY</title>
      <link>https://trid.trb.org/View/215887</link>
      <description><![CDATA[The publication was prepared for a series of courses in traffic science run at Monash University in September 1984. The following papers were presented at the course: Introduction to the Theory of Traffic Flow (Allsop, RE); Basic Traffic Flow Relationships (Gipps, PG); The Performance of Roads (Taylor, MAP); Principal Distributions Relevant to Traffic Flow (Gipps, PG); The Distribution of Speeds and Gaps in Traffic Systems (Taylor, MAP and Young, W); Car-Following Models (Gipps, PG); Queueing Theory Applications in Traffic Flow (Gipps, PG); Bunching on Two Lane Rural Roads (Hoban, CJ); Performance of Signalised Intersections (Young, W); Delay at Signal Controlled Junctions Operating Within but Near to Capacity (Allsop, RE); Signal Linking and Platoon Dispersion (Gipps, PG); Priority for Buses at Traffic Signals (Allsop, RE); GAP Acceptance at Major-Minor Intersections (Gipps, RE); The Theory of Traffic Flow on Roundabouts (Troutbeck, RJ); Fuel Consumption Modelling (Richardson, AJ).  (TRRL)]]></description>
      <pubDate>Wed, 31 Jul 1985 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/215887</guid>
    </item>
    <item>
      <title>ADAMS' FORMULA REVISED</title>
      <link>https://trid.trb.org/View/211439</link>
      <description><![CDATA[The author presents a revised form of Adams' formula for determining the expected delay to a pedestrian wishing to cross a traffic stream.  The original formula uses the Poisson process as a statistical model for the traffic stream.  Real traffic streams, however, have a tendency to form bunches with gaps between the bunches and these features are not modelled by the Poisson process.  The derivation of the new average delay formula is given in an appendix.  Representative curves relating average delay and traffic flow rate are shown for different distributions of bunches and bunch size.  They demonstrate that average delay is sensitive to the bunch gap structure of traffic. Importantly, the new results are sufficiently different from those given by Adams' original formula that a revision of practical traffic warrents involving pedestrian facilities seems desirable.  (TRRL)]]></description>
      <pubDate>Fri, 31 May 1985 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/211439</guid>
    </item>
    <item>
      <title>A BASIC ALGORITHM FOR DYNAMIC ADVISORY SPEED SIGNS TO REDUCE STOP, TRAVEL TIME AND FUEL CONSUMPTION</title>
      <link>https://trid.trb.org/View/210464</link>
      <description><![CDATA[This paper examines the requirements and advantages of dynamic advisory speed signs and focuses on the basic algorithms necessary.  An algorithm is given to meet the situation where the speed-advised driver is approaching a red signal about to turn green.  Assumptions regarding the road geometry and braking performance are included. Platoon behaviour and driver compliance to the signs are discussed, and it is concluded that several conditions must be met to realise the full benefits of advisory speed signs. (Author/TRRL)]]></description>
      <pubDate>Sun, 30 Dec 1984 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/210464</guid>
    </item>
    <item>
      <title>TOWARDS A REVIEW OF THE CONCEPT OF LEVEL OF SERVICE FOR TWO- LANE RURAL ROADS</title>
      <link>https://trid.trb.org/View/201628</link>
      <description><![CDATA[The concept of level of service has been widely used in assessing traffic performance for various road and traffic conditions.  For rural roads, however, the existing definitions have a number of deficiencies.  This note considers some of these deficiencies and suggests a new set of criteria based on traffic bunching (or platooning). Bunching appears to closely reflect the quality of rural traffic operations as perceived by the driver, and it has the advantage of being easy to measure in the field.  The rural traffic simulation model trarr was used to derive bunching criteria which correspond to the existing level of service definitions.  Suggested maximum bunching criteria for levels of service A, B, C and D respectively are 30, 60, 75 and 80 per cent of journey time spent following in bunches.  The new criteria were applied to 24 simulated road conditions to derive approximate service volumes for each case.  It was found that these were easily defined in terms of bunching and automatically took account of changes in driver expectations on differen road types.  (Author/TRRL)]]></description>
      <pubDate>Mon, 30 Apr 1984 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/201628</guid>
    </item>
    <item>
      <title>THE TWO AND A HALF LANE RURAL ROAD</title>
      <link>https://trid.trb.org/View/186367</link>
      <description><![CDATA[Two major methods of improvement for two-lane rural highways are realignment to a higher design speed, and upgrading to a four-lane divided road.  An intermediate alternative which is now receiving some attention is the systematic provision of short overtaking lanes along the two-lane road, in effect creating a "two and a half lane road".  Recent studies have indicated that overtaking lanes may offer substantial benefits in travel time, level of service and safety at comparatively very low costs.  This paper uses traffic simulation to compare different options for rural road improvement and to investigate the effects of each option on traffic speeds, bunching and travel times. Construction costs and expected accident reductions are also considered, in order to derive overall measures of the relative cost-effectiveness of each option.  The results suggest that the "two and a half lane road" may be a practical and effective alternative to both realignment and duplication of two-lane roads, offering many of the benefits of these improvements at much lower costs.  The selective stage construction of long duplication projects is also shown to have many of the advantages of overtaking lanes (a). The number of the covering abstract of the conference is TRIS No. 368448.  (TRRL)]]></description>
      <pubDate>Thu, 30 Dec 1982 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/186367</guid>
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