Sidra Intersection (styled SIDRA, previously called Sidra and aaSidra) is a software package used for intersection (junction), interchange and network capacity, level of service, performance and traffic impact analysis, and signalised intersection, interchange and network timing calculations by traffic design, operations and planning professionals.

First released in 1984, it has been under continuous development in response to user feedback. Version 6.0 released in April 2013 added network modelling capability and new vehicle movement classes. Version 7.0 released in April 2016 included new timing analysis methods for Common Control Groups (multiple intersections operating under one signal controller) and Network Cycle Time and Signal Offset calculations for signal coordination.

Version 9.0 released in May 2020 included improved network model processing efficiency and workflow efficiency through substantial user interface enhancements and model improvements.

Version 9.1 introduced important traffic model enhancements and extensive user interface and model output improvements including network layout and roundabout layout enhancements, and customised reports and displays. The model enhancements include output by Movement Class, a new Variable Demand model, upstream delay and stop rate model for approach short lanes, the HCM Edition 6/7 Extended Roundabout Capacity Model and a combined pedestrian actuation and minor phase actuation method for signal timing calculations.

Version 10 introduced significant updates and enhancements, including a new future-proof, versionless project file format (.sipx) designed for compatibility, reduced file sizes, and faster processing. It also features efficient volume data management through the new Volume Store, eliminating duplication of Sites and Networks for more streamlined Scenario Analysis. SIDRA MAPS integrates OpenStreetMap (OSM) data for advanced visualisation and site creation directly from map data. The software expands modelling capabilities with new Site Types—Turbo Roundabouts, Arterial Segments, Freeway Segments, and Freeway Segments with Ramps—and enhances signal timing analysis with real-number timings, multiple green periods, and improved performance models. Additional model enhancements include refined queue modelling and a new Exit Merge Queue Model. User interface improvements provide a redesigned ribbon, drag-and-drop functionality, and advanced search and import tools for easier navigation. Additionally, the updated VOLUMES Excel Utility allows seamless integration and processing of volume-related data directly within Excel.

SIDRA INTERSECTION 11 was released in March 2026. It introduced major new features and various improvements. These include SIDRA ASSIGN (new traffic assignment module), use of Origin-Destination (O-D) Matrix Data for ASSIGN, SIDRA Glossary update including traffic assignment terms, enhanced Network Convergence method including a new Two-Loop Convergence process, improved User Interface for User Report Template dialogs, website changes including the implementation of new DOCS formatting, various model parameter updates, improvements to platoon modelling and proportion queued for oversaturated cases for multiple green periods, and user interface improvements. New Software Licensing including Personal and Team Subscription Licence products has been introduced.

Sidra Intersection is a micro-analytical traffic evaluation tool that employs lane-by-lane and vehicle drive cycle models. It can be used to compare alternative treatments of individual intersections and networks of intersections involving signalised intersections (fixed-time/pretimed and actuated), roundabouts (not signalised), roundabouts with metering signals, fully signalised roundabouts, two-way stop and give-way (yield) sign control, all-way (4-way and 3-way) stop sign control, merging, single-point urban interchanges, traditional diamond and diverging diamond interchanges, basic freeway segments, signalised and unsignalised (zebra) midblock crossings for pedestrians, merging analysis and network modelling of these intersection and interchange types. Sidra Intersection allows modelling of separate Movement Classes (Light Vehicles, Heavy Vehicles, Buses, Bicycles, Large Trucks, Light Rail/Trams and six User Classes) with different vehicle characteristics. These movements can be allocated to different lanes, lane segments and signal phases; for example for modelling bus priority lanes and signals. In Australia and New Zealand, Sidra Intersection is endorsed by Austroads. In the US, Sidra Intersection is recognised by the US Highway Capacity Manual, TRB/FHWA 2010 Roundabout Guide (NCHRP Report 672) and various roundabout guides.

The lane-by-lane capacity and performance analysis method used by Sidra Intersection includes identifying any de facto exclusive lanes, unequal lane utilisation, lane change, modelling of short lanes (turn bays, lanes with parking upstream, and loss of a lane at the exit side) including delays and stops experienced by drivers in the queue upstream of short lane entry, and lane blockage in shared lanes including lanes containing opposed (permitted) turns, slip (bypass) lane movements and turns on red. Intersections and networks can be modelled in detail using this method and signal timings can be determined accordingly with advantages over approach-based and lane group-based methods.