SIDRA Model is a culmination of 40 years of research and development


SIDRA Model Features

Read a summary of the powerful SIDRA Model features in SIDRA INTERSECTION.

Main features

The SIDRA INTERSECTION network model is a culmination of 40 years of research and development - 20 years at the Australian Road Research Board and more than 20 years at SIDRA SOLUTIONS.

Refer to over 100 research papers and reports on our Publications Page.

Dr Rahmi Akçelik also publishes his work on ResearchGate. His research papers and reports on ResearchGate enjoyed approximately 85,000 reads and about 2,600 citations in eight years.

A unique lane-based micro-analytical model differs from traditional linklane group or approach-based models. This coupled with lane-based vehicle path (drive-cycle) models and an iterative approximation method to solve complex mathematical models provides an advanced micro-analytical traffic evaluation tool.

The Highway Capacity Manual (HCM) Setup in SIDRA INTERSECTION with options for US Customary and Metric units complements the HCM as a lane-based intersection and network analysis tool. Unlike other software packages, the SIDRA HCM Setup does not claim to be a simple replication of the HCM procedures. Instead, it complements the HCM by providing various extensions on the capabilities HCM offers.

SIDRA capacity and performance models are generally compatible with the HCM models in their basic structures and principles. In the HCM Setup, model parameters are calibrated using the HCM defaults.

Refer to HCM articles in our Publications section.


Sites connected to form a Network; up to 50 Sites per Network; 
contra-flow lanes allowed; easy to clone and modify Networks to test alternative treatments.

User-defined Routes for travel performance reports and displays, and Signal Offset calculations.

Signals, roundabouts, sign control, signalised and unsignalised pedestrian crossings

Site and Network templates available including templates for alternative intersections, interchanges, paired intersections, roundabouts and staged crossings

Map Extract tool for new Sites to be created from map data

Light vehicles, heavy vehicles, buses, bicycles, large trucks, light rail/trams and six user-configured classes with different vehicle characteristics (including queue space, speed, acceleration, mass, etc) can be allocated to different lanes, lane segments and signal phases, and signal platoon patterns can be tracked separately.

Used for estimation of unequal lane use at closely-spaced intersections and interchanges; intersection turning volumes layered so as to identify external approach through movements that become turning movements at downstream internal approaches and the dogleg movements between side roads.

Environmental impacts of proposed traffic design, operations and planning schemes can be assessed.

Models calibrated for modern vehicles.

Highly accurate four-mode elemental model (acceleration - cruise - deceleration -idle) applied to vehicle paths of queued and unqueued vehicles in individual lanes.

Design Life, Flow Scale and Parameter Sensitivity analysis for Sites and Networks.

SIDRA API provides a programming interface that enables external applications to communicate with SIDRA INTERSECTION to achieve more. 

VOLUMES utility helps users as a simple application of SIDRA API. 

Network model

Analytical model based on the probability of blockage of upstream lanes by downstream queues at all types of facilities.
Back of queue extending upstream at intermediate locations with continuous lanes including major roads at sign-controlled intersections modelled.

Dynamic saturation flow estimation to allow for upstream lane capacity losses due to lane blockage with effect on signal timing calculations.

Exit flow rates from oversaturated upstream lanes entering downstream lanes are limited to capacity flow rates (arrival flow rates differ from demand flow rates).

Network-wide iterative process to find a capacity - performance solution that balances the opposing effects of queue spillback (lane blockage) and capacity constraint, with corresponding signal timing solution where applicable.

Flow proportions for lane movements from each approach lane to each exit lane can be specified; relevant to modelling forward movement of platoon patterns and backward effect of lane blockages.

Site turning volumes (approach-movement demand flow rates) used.

Determined from Site approach-movement demand flow rates; significant effect on signal platoon modelling.

Determined from upstream and downstream lane flow rates to allow the user to calibrate external approach lane use. 

Basic model elements

Key parameter to estimate lane-based probabilities of blockage or overflow in queue spillback and short lane models with percentile queue modelling; used for signals as well as gap-acceptance processes (roundabouts and sign control). 

Complex multiple short lane configurations modelled. 
Blockage of upstream intersection lanes by short lane queues that overflow into full-length lanes at a downstream intersection modelled.

Blockage of movements with different signal control characteristics blocking each other in shared lanes modelled using the free queue method.

Merge Model for exit short lanes at any type of intersection with Priority Merge and Zipper Merge operations.

Available at all Site types; U-Turn before intersection available at signalised and unsignalised Sites.

Continuous movement (uninterrupted flow) model with detailed performance estimates.

Extensive treatment of signalised and unsignalised (zebra) pedestrian crossings at intersections and midblock locations.

Effect of pedestrian movements on signal timings (including pedestrian actuation feature).

Delays and other performance estimates for pedestrian movements at signalised intersections. 

Effect of pedestrians on capacity and performance of vehicle movements.

Staged pedestrian crossings with selectable elements (approach or exit side crossing can be specified as not existing) 

Unsignalised (zebra) crossings on slip / bypass lanes at all types of intersection. 



Roundabout capacity and performance models developed as part of an integrated performance modelling framework developed considering all types of intersection allows comparison of roundabout design with signalised and sign-controlled intersections in one package using consistent methodology.

Roundabouts with 2 or more entry and circulating lanes with any configuration. 

Roundabout corridors and networks with signals, sign-controlled intersections and pedestrian crossings. 
Roundabout Level of Service option. 

Negotiation speeds and distances and geometric delays estimated.

Capacity constraint method applied to oversaturated lanes as an essential element of roundabout analysis.

Roundabout is treated as an interactive system for modeling of unbalanced flow conditions.

Effect of upstream signals on capacity is taken into account by determining extra bunching in circulating flows.

Unique method for analysis of metering signals on one leg of the roundabout.

Environment Factor parameter for easy model calibration for different local conditions. 

The effects of driver yield behaviour and roundabout geometry factors on capacity and level of service are taken into account using a unique lane-by-lane analysis method combined with gap-acceptance parameters that are empirically based.

The effect of roundabout geometry parameters (roundabout size, circulating road width, entry radius, entry angle, etc.) on capacity included.

Critical Gap and Follow-Up Headway Reduction with increasing demand flows in design life analysis.

Effect of Heavy Vehicles and other Movement Classes on capacity taken into account using the Gap Acceptance Factor and Opposing Vehicle Factor parameters.

The US HCM Software Setup in SIDRA INTERSECTION uses the HCM Edition 6 roundabout capacity model as the default model, continues to offer the HCM 2010 roundabout capacity model option, and offers the SIDRA Standard (HCM) roundabout capacity model option calibrated for HCM with default Environment Factors of 1.05 for single-lane roundabouts and 1.20 for two-lane roundabouts to match the lower capacity estimates based on US roundabout research. Roundabout Capacity Model in HCM Edition 7 is the same as the model in HCM Edition 6.

Articles comparing the features of SIDRA Standard model, HCM model described in Highway Capacity Manual Edition 6, and the UK TRL model implemented in the RODEL and ARCADY software can be found under Publications

The features compared include methodology, model level of detail (lane-based or approach-based), parameters used in the model to represent driver behaviour and roundabout geometry, and model calibration methods. 

Signal Timings

Cycle time and phase times: 

Practical cycle time, optimum cycle time and user-given cycle time with program-determined and user-given phase times.

Offsets for signal coordination:

Calculated for Routes defined by users.

Interactive Offsets function allows the user to modify Offsets manually towards achieving desired two-way signal progressions.

Offset calculations and platoon progression with continuous lanes between two signalised intersections

Signal timing method for several signalised intersections operating under one signal controller as a single entity.

Timing analysis using group control methodology treating vehicle turning movements by Movement Class (light and heavy vehicles, buses bicycles, and so on) and pedestrian movements individually. 

Fixed-time / pretimed, SCATS-like EQUISAT, actuated and semi-actuated signal analysis methods.

Simple and complex phasing arrangements; variable phasing analysis.

ARR 123 critical movement identification method.

Green split priority for coordinated movements.

Undetected movements and phase transition methods.

Pedestrian actuation (variable pedestrian minimum time effects).

Minor phase actuation (phase skipping); phase frequency adjustments.

Late start and early cut-off.

Red arrow drop off.

Give-way / yield controlled and continuous slip / bypass lanes.

Turn On Red (gap acceptance method for capacity estimation).

SCATS parameters output.

Signal platoons

Lane-based method to determine second-by second arrival and departure flow patterns as a function of Signal Offsets including a unique platoon dispersion model.

Midblock lane changes and midblock inflows and outflows taken into account when moving signal platoon patterns between intersections.

Second-by-second signal platoons modelled and tracked for each Movement Class separately.

Effect of upstream signals on gap-acceptance capacity of roundabouts and two-way sign-controlled intersections modelled by increased bunching.


Routes can be defined in a very flexible way for travel performance results and signal offset calculations.

Route travel time and average travel speed estimates can be used for model calibration.

Route travel times include geometric delays, acceleration and deceleration delays for oversaturated conditions, travel times include delays experienced until all vehicles arriving during the analysis period have departed.

Site, network and route output

Users can define User Report Templates to include selected output report and display elements (tables, graphical displays).

Users can select the elements (tables, graphical displays) that they wish to include in standard reports and displays.

PDF Output function is available to save the output reports and displays in a PDF report.

Approach Displays, Lane Displays, Movement Displays, Lane Flows, Movement Flows displays for Sites, Networks and Routes, and Midblock Flow and Lane Changes displays for Networks and Routes presented consistently.  Other reports are listed below.  

Diagnostics, Network Summary, Network Graphs, Network Variable Run Phase Timings, Signal Offsets.

Route Summary, Route Travel Performance, Time-Distance diagram (one or two directions).

Diagnostics, Detailed Output, Intersection Summary, Movement Summary, Lane Summary, Fuel, Emissons & Cost, Queue Analysis, Lane Blockages, Lane Changes, Graphs, Variable Run, Lane LOS, Demand Flows.

Phasing Summary, Timing Analysis, Movement Timing, Saturation Flows Signal Coordination, Multiple Sequence Analysis, Pedestrian Analysis.

Roundabout Analysis, Roundabout Metering, Sign Control Analysis.

Input Comparison reports for Sites and Networks.

Output Comparison reports for Sites, Networks and Routes.

Project Summary report.

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