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Rahmi Akçelik

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Dr Akçelik (pronounced Ak-chelik) is a Director at Akcelik & Associates (trading as SIDRA SOLUTIONS). He is a leading scientist and software developer with over 300 technical publications in his area of expertise. Dr Akçelik leads the SIDRA SOLUTIONS software development team and contributes to software design and technical specifications, user training and technical support.

He graduated as a Civil Engineer from Istanbul Technical University (1968), and received a Ph.D. in Transportation Engineering from Leeds University, England. He migrated to Australia in 1975. He worked as a traffic engineer-planner with the National Capital Development Commission, Canberra (1975-79), and as a researcher with ARRB Transport Research, Melbourne (1979-1999). In 1999, Dr Akçelik established Akcelik and Associates Pty Ltd as a research and software company specialising in the area of road traffic operations, traffic engineering, management and control.

Awards received by Dr Akçelik include the 2014 Roads Australia Award for Technical Excellence in recognition of the exceptional achievement of an individual in a technical or scientific area relevant to transport, the 1999 Clunies Ross National Science and Technology Award for outstanding commitment and contribution to the application of science and technology in Australia, the 2008 Institute of Transportation Engineers Australia and New Zealand Section Contribution to the Transportation Profession Award, and the 1986 Institute of Transportation Engineers (USA) Transportation Energy Conservation Award in Memory of Frederick A. Wagner for research into energy savings from urban traffic.

Dr Akçelik served as member of the US Transportation Research Board (TRB) Committees on Highway Capacity and Quality of Service (HCQS), and Traffic Signal Systems. He made various contributions to the US Highway Capacity Manual. He has trained several thousand professionals in over 250 workshops, courses and seminars.

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Dimitrios E VENTZAS

UNIVERSITY OF THESSALY, GREECE

Danang university of technology

Università degli Studi "La Sapienza" di Roma

PRASANNA KUMAR R

Geethanjali college of Engineering and technology

Universiti Teknologi Malaysia - UTM

Prashant Bokare

Indian Institute of Technology Guwahati

Assosa University(asuedu.et)

University of East London

Gwen Robbins Schug

University of North Carolina at Greensboro

Gabriel Gutierrez-Alonso

University of Salamanca

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Papers by Rahmi Akçelik

Gap Acceptance Cycles for Modelling Roundabout Capacity and Performance

Lecture notes in networks and systems, Aug 1, 2018

The Re-Distributional Effects of an Area Traffic Control Policy

Traffic engineering and control, 1975

The purpose of this paper is fourfold: to point out that the assessment of the benefits of an ATC... more The purpose of this paper is fourfold: to point out that the assessment of the benefits of an ATC scheme cannot be made properly without consideration of the re-distributional effects; to emphasise the importance of the interaction between ATC signal plans and traffic flow patterns; to show that the continual optimisation of signal plans can lead to a gradual deterioration of the network performance; and to demonstrate that traffic management measures (such as the banning of turning movements and the introduction of one-way schemes), and route control ideas, can be applied in conjunction with ATC policies to improve the performance of a network. (A) /TRRL/

An Investigation of Pedestrian Movement Characteristics at Mid-Block Signalised Crossings

Guide to Traffic Engineering Practice: Part 7: Traffic Signals. 3RD Ed

Guide to Traffic Engineering Practice Series, 2003

This guide provides a comprehensive coverage of traffic surveys, analysis, layout, design, traffi... more This guide provides a comprehensive coverage of traffic surveys, analysis, layout, design, traffic management and road safety standards and practices in Australia. To date, 15 parts of the guide have been published. Part 7 Traffic Signals (2003) is a major revision of the 1993 publication. It incorporates the latest practice in the safe and efficient design of traffic signal installations. It presents detailed information and provides guidelines on collection of design data, geometric elements, signal system and components, signal face layouts and display sequences, signal phasing, location of signal equipment, traffic detection, signal controllers, pavement markings, signs, electrical design, coordination of traffic signals, installation checks and maintenance, and special applications including advanced warning signals, emergency vehicle facilities, public transport priority, bicycle facilities, roundabout metering signals, ramp-metering signals, special intersection treatments, overhead lane-control signals, single-lane operation and portable signals, left turn on red, and metering signals at sign-controlled intersections. (a)

TRBRouConf2011 AKCELIK HCM2010 Presentation. TRB International Conference; Carmel; May 2011

A new lane-based model for platoon patterns at closely-spaced signalised intersections

An analytical lane-based method for determining platoon patterns at closely-spaced signalised int... more An analytical lane-based method for determining platoon patterns at closely-spaced signalised intersections is discussed. The method has been developed for the SIDRA INTERSECTION software. The traditional network models using "links" or "lane groups" based on aggregation of individual lane conditions cannot provide sufficient information about departure and arrival patterns, queue lengths, lane blockage probabilities, backward spread of queues, and so on at a lane level. These are important in modelling signal platoon patterns for estimating performance measures (delay, back of queue, stop rate). This is particularly important in evaluating closely-spaced intersections with high demand flows where vehicles have limited opportunities for lane changing between intersections. The new lane-based method derives second-by-second downstream arrival patterns in accordance with above requirements. Modelling of departure patterns at upstream lanes takes into account (i) pr...

Estimating negotiation radius, distance and speed for vehicles using roundabouts

… Conference of Australian Institutes of Transport …, 2002

This paper discusses models for estimating negotiation radius, distance and speed values of throu... more

Evaluating Roundabout Capacity, Level of Service and Performance

Results of research on roundabouts in the United States are presented in the NCHRP Report 572. Th... more Results of research on roundabouts in the United States are presented in the NCHRP Report 572. The findings and recommendations of this report are important as they will be the basis of the 2010 Highway Capacity Manual methodology for operational analysis of roundabouts. This paper discusses various findings and recommendations of the NCHRP Report 572 on roundabout capacity and level of service. Discussions include issues related to the finding of lower capacity of roundabouts in the USA compared with Australian and UK roundabouts, and the choice of Level of Service (LOS) thresholds for roundabouts compared with those used for signalized and sign-controlled intersections. Capacity and the resulting degree of saturation (v/c ratio) estimates obtained using the NCHRP Report 572 and standard SIDRA INTERSECTION methods are compared by presenting single-lane and multi-lane roundabout examples. Importance of the basic findings of research on US roundabouts as presented in the NCHRP Report...

Analysis of Roundabout Metering Signals

There are many examples of roundabouts with unbalanced flow patterns in Australia, where part- ti... more There are many examples of roundabouts with unbalanced flow patterns in Australia, where part- time roundabout metering signals are used to create gaps in the circulating stream in order to solve the problem of excessive queuing and delays at approaches affected by highly directional flows. The use of metering signals is a cost-effective measure to avoid the need for a fully-signalized intersection treatment. A case study is presented comparing a roundabout with and without metering signals in terms of operating cost, fuel consumption and pollutant emissions as well as delay and degree of saturation.

Analytical and Microsimulation Model Calibration and Validation: Application to Roundabouts under Sight-Restricted Conditions

Transportation Research Record: Journal of the Transportation Research Board

Analytical models and traffic microsimulation are two widely used platforms for evaluating rounda... more Analytical models and traffic microsimulation are two widely used platforms for evaluating roundabout operations. The application of the correct inputs and proper specification of calibration parameters should precede the actual simulation, to replicate field traffic conditions. In this sense, simultaneous data collection and estimation of the input, calibration, and validation variables, along with knowledge of their definitions, are crucial. Although simultaneity of data gathering is virtually guaranteed with the use of wide-frame videos captured with an unmanned aerial system (UAS), there are cases where sight distance restrictions may obscure observations of the back of queue and arrival patterns. This paper explores the calibration and validation efforts associated with an analytical platform, SIDRA 9, and a microsimulation model, TransModeler 5, conducted under sight-restricted conditions. Video captured from a drone, followed by trajectory extraction using video processing so...

Further work on modelling car fuel consumption

Four fuel consumption models are described which cover the range of applications in urban traffic... more Four fuel consumption models are described which cover the range of applications in urban traffic management. The models are all interrelated and keep the same set of vehicle characteristics as explicit parameters. An extension to the power (energy) model of car fuel consumption is described which considerably improves the model's accuracy, especially during hard accelerations. Drag power is estimated using steady speed fuel consumption data to ensure that the three components, rolling, engine and aerodynamic drag are all included. Functions for estimating acceleration, cruise and deceleration fuel consumption are developed by integration of the extended power model. These are used to form a four mode elemental model of fuel consumption which is very flexible in both its range of applications and data requirements. A model similar to the pke model called the running speed model is developed from the cruise fuel consumption function. The average travel speed model is related to t...

Limitations on the Objective of Energy Efficiency in Urban Traffic Management

Publication of: Society of Automotive Engineers, 1982

The objective of reducing fuel consumption in urban traffic must be considered in the context of ... more The objective of reducing fuel consumption in urban traffic must be considered in the context of an overall traffic system management approach. This paper emphasises the existence of conflicts among various traffic management objectives (safety, traffic performance, energy, air pollution, property access, intrusion into residential areas, etc) and among the needs of different road user groups (pedestrians, buses, cars, heavy vehicles, major and minor road traffic, etc). An elemental model of fuel consumption is described briefly, and its relevance to existing traffic modelling techniques is emphasised. The elemental model is then used as a basis for discussing the expected impacts of various short-term traffic management measures on traffic performance, fuel consumption, safety and other objectives. Theoretically, fuel consumption savings of about 5 to 10 per cent could be achieved from traffic control (at a local level) given the limitations imposed by other traffic system manageme...

Capacity Research and Its Application in Australia

A country report summarising highway capacity research and applications in Australia was presente... more A country report summarising highway capacity research and applications in Australia was presented at the First Internationa Symposium on Highway Capacity held at Karlsruhe. This report presents a summary of the capacity research progress undertaken at the Australian Road Research Board, universities and state road traffic authorities since the last symposium. The subjects covered include signalised intersections, roundabouts, other unsignalised intersections, vehicle-actuated signals, dynamic control of traffic signals, saturation flows, pedestrian-vehicle interaction, paired intersections, arterial road performance, network analysis, shopping centre design, rural roads and freeways, fuel consumption and emissions, accidents at roundabouts, intersection design and packages of software integration. References to publications and a brief list of staff involved in capacity research in Australia are given at the of the report. (a)

Introduction to sidra-2

Sidra Version 2.2 Output: User Guide Section 3

Guide to traffic management part 9: traffic operations

The Austroads Guide to Traffic Management consists of 13 parts and provides a comprehensive cover... more The Austroads Guide to Traffic Management consists of 13 parts and provides a comprehensive coverage of traffic management guidance for practitioners involved in traffic engineering, road design and road safety. Part 9: Traffic Operations is concerned with the day-to-day operations that support the provision of road services to road network users. It introduces the concept of traffic operations as underpinning road user services, covers the major types of services provided and outlines the role of intelligent transport systems (ITS) in delivering these services. Part 9 provides guidance on the configuration and operation of systems, both ITS and manual, supporting traffic operations including network monitoring systems, incident management, traffic signal systems, congestion management, freeway/motorway management systems, traveller information systems and the like. This is the second edition of Part 9 of the Guide to Traffic Management. This edition incorporates a number of changes...

Validation of a power based model of car fuel consumption

A power based model of car fuel consumption has recently been proposed but the model validation w... more A power based model of car fuel consumption has recently been proposed but the model validation was inadequate. This report describes the power model in detail, explores the areas of use of the model and documents a thorough investigation of the calibration procedure and prediction errors. Extensive dynamometer and on road data, including data from well controlled on road acceleration, deceleration and steady speed tests, were used in the validation task. The on road drag power was found to be best estimated by a two term function of speed (v and v**3) using coast down or steady speed fuel consumption data. The efficiency parameter of the power model was found to be dependent on the calibration data, and hence the choice of the data is very important. Model parameters should be estimated independently where possible using second by second speed and fuel consumption data. A procedure is outlined for parameter estimation when fuel consumption cannot be measured accurately in one secon...

Comparing Lane Based and Lane-group Based Models of Signalised Intersection Networks

Transportation Research Procedia, 2016

This paper compares two analytical approaches for modelling signalised intersection networks in r... more This paper compares two analytical approaches for modelling signalised intersection networks in relation to the assessment of signal coordination quality as a fundamental element of network performance analysis. These are (i) the traditional model based on using "lane groups" or "links" through aggregation of individual lane conditions, and (ii) a new "lane-based" model of upstream departure and downstream arrival patterns as well as midblock lane changes between upstream and downstream intersections, and the resulting proportions of traffic arriving during the green period at an individual lane level. The latter is part of a lane-based network model that involves blockage of upstream intersection lanes by downstream queues (queue spillback) and capacity constraint applied to oversaturated upstream intersections. The differences between the two models are expected to be particularly important in evaluating closely-spaced intersections with high demand flows where vehicles have limited opportunities for lane changes between intersections. The lane-based model can make use of "special movement classes" for assigning specific movements to separate lanes and separate signal phases, and tracking of their second-by-second platoon patterns through the network separately. The paper presents a staggered T network example to demonstrate important aspects of modelling signal platoon patterns by approach lane use and movement class, and to compare the resulting traffic performance measures (delay, back of queue, level of service) with those estimated using the traditional method based on lane groups or links.

Roundabouts in Australia

This paper presents a collation of comments received from Australian traffic and transport profes... more This paper presents a collation of comments received from Australian traffic and transport professionals in response to a survey about the current status of roundabouts in Australia. The survey posed questions related to the extent to which roundabouts are being built, replacement of roundabouts with signals or signals with roundabouts, use of roundabouts with metering signals and fully-signalised roundabouts, the public's view on roundabouts, educating road users (drivers, cyclists, pedestrians) to use roundabouts correctly, current experience with roundabouts in terms of efficiency (delays, congestion), environmental aspects and safety, and the future of roundabouts in Australia.

Alternative Models for Roundabout Capacity

Traffic Engineering Control, Jul 1, 2012

This article provides a wide perspective about roundabout capacity models. Although there are man... more This article provides a wide perspective about roundabout capacity models. Although there are many roundabout capacity models used around the world, this article focuses on two well known models. The SIDRA model, which is based on research on roundabouts in Australia and the TRL method, which is based on research on roundabouts in the United Kingdom. A detailed table that compares the features of these two capacity models is provided. The comparison table also includes the United States (US) Highway Capacity Manual 2010 (HCM2010) model based on research on roundabouts in the US. Developed in different countries at different times, these models have common elements yet significant differences in modeling methodologies.

Gap Acceptance Cycles for Modelling Roundabout Capacity and Performance

Lecture notes in networks and systems, Aug 1, 2018

The Re-Distributional Effects of an Area Traffic Control Policy

Traffic engineering and control, 1975

The purpose of this paper is fourfold: to point out that the assessment of the benefits of an ATC... more The purpose of this paper is fourfold: to point out that the assessment of the benefits of an ATC scheme cannot be made properly without consideration of the re-distributional effects; to emphasise the importance of the interaction between ATC signal plans and traffic flow patterns; to show that the continual optimisation of signal plans can lead to a gradual deterioration of the network performance; and to demonstrate that traffic management measures (such as the banning of turning movements and the introduction of one-way schemes), and route control ideas, can be applied in conjunction with ATC policies to improve the performance of a network. (A) /TRRL/

An Investigation of Pedestrian Movement Characteristics at Mid-Block Signalised Crossings

Guide to Traffic Engineering Practice: Part 7: Traffic Signals. 3RD Ed

Guide to Traffic Engineering Practice Series, 2003

This guide provides a comprehensive coverage of traffic surveys, analysis, layout, design, traffi... more This guide provides a comprehensive coverage of traffic surveys, analysis, layout, design, traffic management and road safety standards and practices in Australia. To date, 15 parts of the guide have been published. Part 7 Traffic Signals (2003) is a major revision of the 1993 publication. It incorporates the latest practice in the safe and efficient design of traffic signal installations. It presents detailed information and provides guidelines on collection of design data, geometric elements, signal system and components, signal face layouts and display sequences, signal phasing, location of signal equipment, traffic detection, signal controllers, pavement markings, signs, electrical design, coordination of traffic signals, installation checks and maintenance, and special applications including advanced warning signals, emergency vehicle facilities, public transport priority, bicycle facilities, roundabout metering signals, ramp-metering signals, special intersection treatments, overhead lane-control signals, single-lane operation and portable signals, left turn on red, and metering signals at sign-controlled intersections. (a)

TRBRouConf2011 AKCELIK HCM2010 Presentation. TRB International Conference; Carmel; May 2011

A new lane-based model for platoon patterns at closely-spaced signalised intersections

An analytical lane-based method for determining platoon patterns at closely-spaced signalised int... more An analytical lane-based method for determining platoon patterns at closely-spaced signalised intersections is discussed. The method has been developed for the SIDRA INTERSECTION software. The traditional network models using "links" or "lane groups" based on aggregation of individual lane conditions cannot provide sufficient information about departure and arrival patterns, queue lengths, lane blockage probabilities, backward spread of queues, and so on at a lane level. These are important in modelling signal platoon patterns for estimating performance measures (delay, back of queue, stop rate). This is particularly important in evaluating closely-spaced intersections with high demand flows where vehicles have limited opportunities for lane changing between intersections. The new lane-based method derives second-by-second downstream arrival patterns in accordance with above requirements. Modelling of departure patterns at upstream lanes takes into account (i) pr...

Estimating negotiation radius, distance and speed for vehicles using roundabouts

… Conference of Australian Institutes of Transport …, 2002

This paper discusses models for estimating negotiation radius, distance and speed values of throu... more

Evaluating Roundabout Capacity, Level of Service and Performance

Results of research on roundabouts in the United States are presented in the NCHRP Report 572. Th... more Results of research on roundabouts in the United States are presented in the NCHRP Report 572. The findings and recommendations of this report are important as they will be the basis of the 2010 Highway Capacity Manual methodology for operational analysis of roundabouts. This paper discusses various findings and recommendations of the NCHRP Report 572 on roundabout capacity and level of service. Discussions include issues related to the finding of lower capacity of roundabouts in the USA compared with Australian and UK roundabouts, and the choice of Level of Service (LOS) thresholds for roundabouts compared with those used for signalized and sign-controlled intersections. Capacity and the resulting degree of saturation (v/c ratio) estimates obtained using the NCHRP Report 572 and standard SIDRA INTERSECTION methods are compared by presenting single-lane and multi-lane roundabout examples. Importance of the basic findings of research on US roundabouts as presented in the NCHRP Report...

Analysis of Roundabout Metering Signals

There are many examples of roundabouts with unbalanced flow patterns in Australia, where part- ti... more There are many examples of roundabouts with unbalanced flow patterns in Australia, where part- time roundabout metering signals are used to create gaps in the circulating stream in order to solve the problem of excessive queuing and delays at approaches affected by highly directional flows. The use of metering signals is a cost-effective measure to avoid the need for a fully-signalized intersection treatment. A case study is presented comparing a roundabout with and without metering signals in terms of operating cost, fuel consumption and pollutant emissions as well as delay and degree of saturation.

Analytical and Microsimulation Model Calibration and Validation: Application to Roundabouts under Sight-Restricted Conditions

Transportation Research Record: Journal of the Transportation Research Board

Analytical models and traffic microsimulation are two widely used platforms for evaluating rounda... more Analytical models and traffic microsimulation are two widely used platforms for evaluating roundabout operations. The application of the correct inputs and proper specification of calibration parameters should precede the actual simulation, to replicate field traffic conditions. In this sense, simultaneous data collection and estimation of the input, calibration, and validation variables, along with knowledge of their definitions, are crucial. Although simultaneity of data gathering is virtually guaranteed with the use of wide-frame videos captured with an unmanned aerial system (UAS), there are cases where sight distance restrictions may obscure observations of the back of queue and arrival patterns. This paper explores the calibration and validation efforts associated with an analytical platform, SIDRA 9, and a microsimulation model, TransModeler 5, conducted under sight-restricted conditions. Video captured from a drone, followed by trajectory extraction using video processing so...

Further work on modelling car fuel consumption

Four fuel consumption models are described which cover the range of applications in urban traffic... more Four fuel consumption models are described which cover the range of applications in urban traffic management. The models are all interrelated and keep the same set of vehicle characteristics as explicit parameters. An extension to the power (energy) model of car fuel consumption is described which considerably improves the model's accuracy, especially during hard accelerations. Drag power is estimated using steady speed fuel consumption data to ensure that the three components, rolling, engine and aerodynamic drag are all included. Functions for estimating acceleration, cruise and deceleration fuel consumption are developed by integration of the extended power model. These are used to form a four mode elemental model of fuel consumption which is very flexible in both its range of applications and data requirements. A model similar to the pke model called the running speed model is developed from the cruise fuel consumption function. The average travel speed model is related to t...

Limitations on the Objective of Energy Efficiency in Urban Traffic Management

Publication of: Society of Automotive Engineers, 1982

The objective of reducing fuel consumption in urban traffic must be considered in the context of ... more The objective of reducing fuel consumption in urban traffic must be considered in the context of an overall traffic system management approach. This paper emphasises the existence of conflicts among various traffic management objectives (safety, traffic performance, energy, air pollution, property access, intrusion into residential areas, etc) and among the needs of different road user groups (pedestrians, buses, cars, heavy vehicles, major and minor road traffic, etc). An elemental model of fuel consumption is described briefly, and its relevance to existing traffic modelling techniques is emphasised. The elemental model is then used as a basis for discussing the expected impacts of various short-term traffic management measures on traffic performance, fuel consumption, safety and other objectives. Theoretically, fuel consumption savings of about 5 to 10 per cent could be achieved from traffic control (at a local level) given the limitations imposed by other traffic system manageme...

Capacity Research and Its Application in Australia

A country report summarising highway capacity research and applications in Australia was presente... more A country report summarising highway capacity research and applications in Australia was presented at the First Internationa Symposium on Highway Capacity held at Karlsruhe. This report presents a summary of the capacity research progress undertaken at the Australian Road Research Board, universities and state road traffic authorities since the last symposium. The subjects covered include signalised intersections, roundabouts, other unsignalised intersections, vehicle-actuated signals, dynamic control of traffic signals, saturation flows, pedestrian-vehicle interaction, paired intersections, arterial road performance, network analysis, shopping centre design, rural roads and freeways, fuel consumption and emissions, accidents at roundabouts, intersection design and packages of software integration. References to publications and a brief list of staff involved in capacity research in Australia are given at the of the report. (a)

Introduction to sidra-2

Sidra Version 2.2 Output: User Guide Section 3

Guide to traffic management part 9: traffic operations

The Austroads Guide to Traffic Management consists of 13 parts and provides a comprehensive cover... more The Austroads Guide to Traffic Management consists of 13 parts and provides a comprehensive coverage of traffic management guidance for practitioners involved in traffic engineering, road design and road safety. Part 9: Traffic Operations is concerned with the day-to-day operations that support the provision of road services to road network users. It introduces the concept of traffic operations as underpinning road user services, covers the major types of services provided and outlines the role of intelligent transport systems (ITS) in delivering these services. Part 9 provides guidance on the configuration and operation of systems, both ITS and manual, supporting traffic operations including network monitoring systems, incident management, traffic signal systems, congestion management, freeway/motorway management systems, traveller information systems and the like. This is the second edition of Part 9 of the Guide to Traffic Management. This edition incorporates a number of changes...

Validation of a power based model of car fuel consumption

A power based model of car fuel consumption has recently been proposed but the model validation w... more A power based model of car fuel consumption has recently been proposed but the model validation was inadequate. This report describes the power model in detail, explores the areas of use of the model and documents a thorough investigation of the calibration procedure and prediction errors. Extensive dynamometer and on road data, including data from well controlled on road acceleration, deceleration and steady speed tests, were used in the validation task. The on road drag power was found to be best estimated by a two term function of speed (v and v**3) using coast down or steady speed fuel consumption data. The efficiency parameter of the power model was found to be dependent on the calibration data, and hence the choice of the data is very important. Model parameters should be estimated independently where possible using second by second speed and fuel consumption data. A procedure is outlined for parameter estimation when fuel consumption cannot be measured accurately in one secon...

Comparing Lane Based and Lane-group Based Models of Signalised Intersection Networks

Transportation Research Procedia, 2016

This paper compares two analytical approaches for modelling signalised intersection networks in r... more This paper compares two analytical approaches for modelling signalised intersection networks in relation to the assessment of signal coordination quality as a fundamental element of network performance analysis. These are (i) the traditional model based on using "lane groups" or "links" through aggregation of individual lane conditions, and (ii) a new "lane-based" model of upstream departure and downstream arrival patterns as well as midblock lane changes between upstream and downstream intersections, and the resulting proportions of traffic arriving during the green period at an individual lane level. The latter is part of a lane-based network model that involves blockage of upstream intersection lanes by downstream queues (queue spillback) and capacity constraint applied to oversaturated upstream intersections. The differences between the two models are expected to be particularly important in evaluating closely-spaced intersections with high demand flows where vehicles have limited opportunities for lane changes between intersections. The lane-based model can make use of "special movement classes" for assigning specific movements to separate lanes and separate signal phases, and tracking of their second-by-second platoon patterns through the network separately. The paper presents a staggered T network example to demonstrate important aspects of modelling signal platoon patterns by approach lane use and movement class, and to compare the resulting traffic performance measures (delay, back of queue, level of service) with those estimated using the traditional method based on lane groups or links.

Roundabouts in Australia

This paper presents a collation of comments received from Australian traffic and transport profes... more This paper presents a collation of comments received from Australian traffic and transport professionals in response to a survey about the current status of roundabouts in Australia. The survey posed questions related to the extent to which roundabouts are being built, replacement of roundabouts with signals or signals with roundabouts, use of roundabouts with metering signals and fully-signalised roundabouts, the public's view on roundabouts, educating road users (drivers, cyclists, pedestrians) to use roundabouts correctly, current experience with roundabouts in terms of efficiency (delays, congestion), environmental aspects and safety, and the future of roundabouts in Australia.

Alternative Models for Roundabout Capacity

Traffic Engineering Control, Jul 1, 2012

This article provides a wide perspective about roundabout capacity models. Although there are man... more This article provides a wide perspective about roundabout capacity models. Although there are many roundabout capacity models used around the world, this article focuses on two well known models. The SIDRA model, which is based on research on roundabouts in Australia and the TRL method, which is based on research on roundabouts in the United Kingdom. A detailed table that compares the features of these two capacity models is provided. The comparison table also includes the United States (US) Highway Capacity Manual 2010 (HCM2010) model based on research on roundabouts in the US. Developed in different countries at different times, these models have common elements yet significant differences in modeling methodologies.

A COMPARISON OF TWO ROUNDABOUT CAPACITY MODELS

by Rahmi Akçelik and Elżbieta Macioszek

This paper presents the results of a detailed comparison of two roundabout capacity models, namel... more This paper presents the results of a detailed comparison of two roundabout capacity models, namely a model developed by the first author of this paper based on her research conducted in Poland (referred to as the Macioszek model) and the model used in the SIDRA INTERSECTION software based on roundabout research conducted in Australia (referred to as the SIDRA Standard model due to other model options in the software). Both models are lane-based analytical models based on gap acceptance theory with an empirical basis, and both models use Cowan's bunched exponential distribution of circulating road headways. On the other hand, the two models use different capacity and headway distribution equations, and they are calibrated for different traffic conditions in two different countries. Comparisons of entry lane capacity estimates from the two models for one-lane and for two-lane roundabouts are presented. Analyses indicated that the entry lane capacities at one-lane roundabouts in Poland are lower but close to those in Australia whereas the entry lane capacities at two-lane roundabouts in Poland are much lower than those in Australia. Calibrating the SIDRA Standard model using data for 21 one-lane roundabouts and 12 two-lane roundabouts resulted in capacity estimates with very good match to driving conditions in Poland.

An Assessment of the Highway Capacity Manual Edition 6 Roundabout Capacity Model. Paper presented at the 5th International Roundabout Conference, Transportation Research Board, Green Bay, Wisconsin, USA, May 2017.

The latest TRB Highway Capacity Manual (HCM) Edition 6 (2016) introduced major changes to the rou... more The latest TRB Highway Capacity Manual (HCM) Edition 6 (2016) introduced major changes to the roundabout capacity model parameters compared with those given in the HCM 2010 Edition. This paper presents an assessment of the HCM Edition 6 model compared with the HCM 2010 model and the SIDRA Standard capacity model for roundabouts employed in the SIDRA INTERSECTION software which is widely used in US practice. In particular, the Environment Factor parameter used in the SIDRA Standard capacity model is discussed in relation to calibrating the model to match the capacity estimates from the HCM Edition 6 model. Comments are also included on various extensions to the HCM Edition 6 model provided in the SIDRA INTERSECTION software. Using a multilane roundabout example given in the HCM, capacity and the resulting degree of saturation (v/c ratio), delay, level of service and queue length estimates from the HCM Edition 6, HCM 2010 and the SIDRA Standard capacity models are compared.

Recent Innovations and Applications in SIDRA INTERSECTION: Lane-Based Network Model by Rahmi Akçelik

The SIDRA INTERSECTION network model is largely built on the sound foundation of the lane-based m... more The SIDRA INTERSECTION network model is largely built on the sound foundation of the lane-based methodology used in the single intersection model proven via research and used in practice during the last three decades. The network model elements used beyond single intersection modelling are discussed in this presentation. List of relevant documentation is included.

Alternative Intersection Analysis Using SIDRA INTERSECTION ITEANZ Innovative Intersections Seminar Melbourne, 5 Nov 2015 Rahmi Akçelik and Mark Besley Alternative Intersection Analysis Using SIDRA INTERSECTION

Alternative intersection and interchange treatments used in the USA and other countries include D... more Alternative intersection and interchange treatments used in the USA and other countries include Diverging (Double Crossover) Diamond Interchange, Displaced Left-Turn Intersection, Median U-Turn Intersection, Restricted Crossing U-Turn Intersection, and Continuous Flow Intersection. This presentation discusses the modelling of alternative intersections and interchanges in the SIDRA INTERSECTION software. Some useful resources on this subject are given, SIDRA INTERSECTION network modelling features enabling analysis of alternative intersections are introduced, and examples of Diverging Diamond Interchange and Continuous Flow Intersection are given. Performance characteristics of three interchange types, namely a Diverging Diamond Interchange, a traditional Signalised Diamond Interchange and a Roundabout Interchange are compared in an example.

Improvement of the West road corridor for accessing to the new hospital of Lucca

by Rahmi Akçelik and Antonio Pratelli

This paper presents results of the study of a road corridor in the historical city of Lucca, Tusc... more This paper presents results of the study of a road corridor in the historical city of Lucca, Tuscany, Italy. The corridor is about 1.5 km with seven different intersections along the corridor, including signalised and two-way stop controlled intersections and roundabouts. SIDRA INTERSECTION network model was used to analyze two scenarious; namely, the "Present situation" and the "Design situation" to verify the effectiveness of some proposed intersection improvements. The network model results strongly supported the design proposal of improving the West corridor for accessing the new hospital of Lucca. The analyses showed that significant improvements could be made to traffic performance in the road corridor in general, including environmental benefits in terms of reduced fuel consumption and emissions.

Development of Network Signal Timing Methodology in SIDRA INTERSECTION

This presentation discusses main features of the network signal timing methodology which has been... more This presentation discusses main features of the network signal timing methodology which has been under development for the SIDRA INTERSECTION software (current Version 6.1 and the forthcoming Version 7). Direct elements of the network signal timing method includes lane-based second-by-second-platoon model using signal offsets, network cycle time and intersection phase time calculations, signal offset calculations, and common control groups (for signalised intersections controlled by a single signal controller). The general aspects of the network model that affects network signal timing include lane blockage (upstream saturation flow rates are reduced) and capacity constraint (downstream arrival flow rates are reduced) as well as the lane movements at the upstream intersection and the midblock lane changes affecting downstream platoon patterns.

Roundabouts in Australia: the state of the art on models and applications Seminar Presentation One-day International Meeting on Roundabouts

This presentation discusses various aspects of roundabouts in Australia and gives a detailed summ... more

Signal platoon patterns by approach lane use and movement class

The modelling of signal platoon patterns is further enhanced by using the Movement Class facility... more The modelling of signal platoon patterns is further enhanced by using the Movement Class facility of the SIDRA INTERSECTION software. This is implemented by assigning two types of movements negotiating the network to Special Movement Classes, namely; (i) Through movements at external approaches which become turning movements at downstream internal approaches, and (ii) dogleg movements at staggered T intersections. These movements can be assigned to separate lanes and separate signal phases, and their arrival and departure flow patterns (second-by-second platoon patterns) including lane changes determined by the program can be tracked through the paired intersection system separetely. This improves the quality of signal platoon modelling, and is expected to produce better results in assessing signal coordination quality and optimising signal offsets. The use of Special Movement Classes also helps to estimate unequal lane use cases at external approaches of a paired intersection system, a factor which also affects signal platoon patterns. A variation to the staggered T-intersection example included in the 26th ARRB Conference paper (Akçelik 2014) is presented to demonstrate the difference in performance estimates obtained with and without the use of Special Movement Classes.

Modelling signal platoon patterns by approach lane use and movement class

A lane-based signal platoon progression model has been developed for estimating performance measu... more A lane-based signal platoon progression model has been developed for estimating performance measures as a function of signal offsets, geometric design and flow conditions. the model takes into account midblock lane changes that apply to signal platoon patterns. This particularly important in evaluating closely-spaced intersections with high demand flows where vehicles have limited opportunities for lane changes between intersections. The modelling of signal platoon patterns is further enhanced by assigning two types of movements negotiating the network to Special Movement Classes. These are the through movements at external approaches which become turning movements at downstream internal approaches, and the dogleg movements at staggered T intersections. These movements can be assigned to seperate lanes and seperate signal phases, and their secon-by-second platoon patterns can be tracked through the network separately. A staggered T-intersection example is presented to demonstrate important aspects of modelling signal platoon patterns by approach lane use and movement class.

Comparing Common Control Group treatment and coordination of separate signal controllers NZMUGS 2016 New Zealand Modelling User Group Conference Wellington, September 2016 Rahmi Akçelik

Common Control Group is a SIDRA INTERSECTION software term used for a group of signalised interse... more Common Control Group is a SIDRA INTERSECTION software term used for a group of signalised intersections controlled by a single signal controller. This is relevant to the modelling of signalised paired (closely-spaced) intersections such as staggered T intersections, freeway interchanges, intersections with median area controlled by signals, fully-signalised roundabouts as well as alternative intersection and interchange types such as continuous flow intersection and diverging diamond interchange. The signal timing analysis for a Comm.on Control Group is carried out using a single phase sequence that incorporates all movements at the facility. This differs from the signal timing method for a network of separate intersections with signal coordination. This presentation explains the reason for difference in network performances resulting from the two methods of signal control using a simple example including results from the SIDRA INTERSECTION software

SIDRA GLOSSARY OF ROAD TRAFFIC ANALYSIS TERMS

This glossary has been prepared to include the terminology of the SIDRA INTERSECTION software. T... more This glossary has been prepared to include the terminology of the SIDRA INTERSECTION software. The sources used in preparing this document are the SIDRA INTERSECTION User Guide (2017), the Australian AUSTROADS Glossary, AP-C87-15 (2015) and the US Highway Capacity Manual Edition 6 Glossary (2016). This unique glossary includes many terms that are not included in the Australian AUSTROADS Glossary and the US HCM Glossary. An effort has been made to keep the definitions given in the AUSTROADS and HCM glossaries as much as possible, combine them together, modify as required and incorporate them into the definitions used in the SIDRA INTERSECTION software. The usage in SIDRA INTERSECTION takes precedence where there are discrepancies. Thus, many of the key analysis terms in this glossary have significant differences from those in the AUSTROADS and US HCM glossaries (mostly in the expression but sometimes in the meaning). It is hoped that they represent clearer and more general definitions, for example considering left-hand and right-hand traffic rules and different local traffic engineering practices.