Calibrated using HCM parameters, then extended with capabilities the Manual doesn't cover — by a researcher who helped write it.
Dr Akçelik's research shaped the HCM delay equation, back of queue model, and actuated signal method — SIDRA is built on the same foundations.
Geometry-based roundabout capacity, Common Control Groups, Give-Way modelling, multimodal lane-based analysis — where the HCM stops, SIDRA continues.
SIDRA INTERSECTION and the Highway Capacity Manual share common fundamental traffic modelling principles, and the HCM Software Setup is calibrated using HCM model parameters.
SIDRA ASSIGN estimates intersection movement volumes from Origin–Destination trip demand while accounting for network-wide traffic interactions and detailed intersection capacity estimation at the lane level.
Dr Rahmi Akçelik served as a member of the US Transportation Research Board Committee on Highway Capacity and Quality of Service and its subcommittees. His contributions include:
The second term of the HCM delay equation (Chapters 19–22), correcting an anomaly in earlier editions
The back of queue model for signalised intersections adopted in HCM 2000
The actuated signal analysis method developed jointly with Prof. Courage for HCM 2000
The bunched exponential model of arrival headway distribution
Progression factors for queue length and related performance statistics
Each intersection type has specific areas where SIDRA extends beyond HCM procedures — from five roundabout capacity models to lane-based sign-controlled analysis.
These extensions apply across all intersection types — from multimodal lane-based modelling to environmental outputs the HCM does not produce.
SIDRA INTERSECTION is recognised by the US Highway Capacity Manual, the NCHRP roundabout guides, the FHWA alternative intersections guide, and Austroads.
Complements the HCM — does not simply replicate itsignificant extensions in line with the HCM’s own acknowledgement of the need for alternative models
If you need HCM-compatible analysis with capabilities the Manual doesn’t cover, SIDRA gives you both — calibrated using HCM parameters, then extended where the HCM stops.
SIDRA INTERSECTION and the Highway Capacity Manual share common fundamental traffic modelling principles, and the HCM Software Setup is calibrated using HCM model parameters.
SIDRA ASSIGN traffic assignment modulelane-based route choice modelling integrated with the detailed multimodal SIDRA Network Model
Assess the impact of traffic management schemes on route choice — at the lane level — without exporting to a separate model or purchasing a separate licence.
SIDRA ASSIGN estimates intersection movement volumes from Origin–Destination trip demand while accounting for network-wide traffic interactions and detailed intersection capacity estimation at the lane level.
Built by a researcher who contributed to the HCMDr Rahmi Akçelik’s research made direct contributions to multiple editions of the Highway Capacity Manual
SIDRA doesn’t just implement the HCM — its author helped write it. The delay equation, back of queue model and actuated signal method all draw on Dr Akçelik’s research.
Dr Rahmi Akçelik served as a member of the US Transportation Research Board Committee on Highway Capacity and Quality of Service and its subcommittees. His contributions include:
The second term of the HCM delay equation (Chapters 19–22), correcting an anomaly in earlier editions
The back of queue model for signalised intersections adopted in HCM 2000
The actuated signal analysis method developed jointly with Prof. Courage for HCM 2000
The bunched exponential model of arrival headway distribution
Progression factors for queue length and related performance statistics
These are not adaptations of someone else’s work. SIDRA INTERSECTION is built on the same research that shaped the HCM itself.
Key extensions by intersection typewhere SIDRA extends HCM capabilities for roundabouts, traffic signals and sign-controlled intersections
Analyse intersection types and configurations the HCM cannot handle — geometry-based roundabout capacity, Common Control Groups for signals, and Give-Way modelling for sign control.
Each intersection type has specific areas where SIDRA extends beyond HCM procedures — from five roundabout capacity models to lane-based sign-controlled analysis.
Across all intersection typescapabilities that extend the HCM regardless of facility type
Get environmental outputs the HCM does not provide, back of queue for roundabouts and sign control, and lane-based network analysis with queue spillback and midblock lane changes.
These extensions apply across all intersection types — from multimodal lane-based modelling to environmental outputs the HCM does not produce.
Recognised by the institutions that set the standards
The most widely used roundabout analysis software in the USA according to the Transportation Research Board — and recognised by the HCM, NCHRP, FHWA and Austroads.
SIDRA INTERSECTION is recognised by the US Highway Capacity Manual, the NCHRP roundabout guides, the FHWA alternative intersections guide, and Austroads.
The global standard for roundabout analysis.
Five capacity models. Geometry-based capacity. Lane-by-lane precision. The most widely used roundabout analysis software in the USA.