Overview

"SIDRA INTERSECTION is a very powerful and useful tool for experienced traffic engineers. Its reputation is often tarnished when not used correctly, i.e. when a calibrated base model reflecting current observations is not created. It is user friendly for experienced traffic engineers, especially with reference to the detailed manuals provided. Unfortunately, in large organisations, SIDRA modelling is often assigned to graduates with little knowledge or experience on real life observations and traffic behaviour. The three 'C's to successfull modelling are "Calibrate" "Calibrate" and "Calibrate"."
David Wilkins / i3 consultants WA

"I have used SIDRA in USA, Asia and Australia for 20 years. It has continually improved and over the past six years I have found it extremely useful for analysis of roundabouts in California, Arizona, Oregon and Washington. It is quick and easy to use accurately and my clients respect the results."
Kevin Fehon / DKS Associates

"A great tool to enable students to undertake project work on live intersections as part of the academic syllabus"
Tom Mckune / Durban University of Technology

"I have been using SIDRA for the past 8 years and found all versions are intuitive and the output are very useful and concise for reporting."
Robert Kwok / Worley Parsons

"SIDRA is still our standard for roundabout analysis because of its solid basis in gap acceptance theory that has shown to be more reliable in the USA than empirical models based in other countries."
James Dunlop / NCDOT

"I have found SIDRA INTERSECTION to be a very reliable, versatile and effective tool for analysing intersection performance. The ability to calibrate the model to accurately represent existing intersection characteristics has been of significant benefit for both intersection design and future planning purposes."
Rob Day / RTA (NSW)

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SIDRA INTERSECTION

SIDRA INTERSECTION software (previously called SIDRA and aaSIDRA) is an advanced micro-analytical traffic evaluation tool that employs lane-by-lane and vehicle drive cycle models. SIDRA INTERSECTION is a renowned software package used worldwide for intersection (junction) capacity, level of service and performance analysis by traffic design, operations and planning professionals. SIDRA INTERSECTION incorporates leading analytical methodology based on Dr Akcelik's award-winning research and development work.

Superior Methodologies

SIDRA INTERSECTION, essentially a mathematical model for traffic analysis, has been a valuable technology transfer tool based on extensive research carried out in Australia, USA and elsewhere. It has been developed continuously in response to feedback from practising traffic engineers and planners. This feedback has improved the methods used in SIDRA INTERSECTION and expanded its functionality to cover a wider range of problems. Developed over 30 years, SIDRA INTERSECTION uses one of the most advanced methodologies of any traffic design package.

Intersection Evaluation and Design

SIDRA INTERSECTION model can be used to evaluate and compare capacity, level of service and performance of alternative treatments involving signalised intersections, roundabouts, roundabout metering signals, two-way stop and give-way (yield) sign-control, all-way (4-way and 3-way) stop sign control, single-point urban interchanges, and signalised midblock crossings for pedestrians, all in one package. This is unlike other software such as ARCADY, PICADY and OSCADY from TRL (UK) which model different types of intersections in separate packages. Intersections with up to 8 legs (approaches), each as a two-way road, one-way approach or one-way exit can be modelled with ease. Templates are provided for analysis of zebra crossings, merging and basic freeway segments. Provision is made for analysis of closely-spaced intersections.

Model Calibration

SIDRA INTERSECTION provides facilities to calibrate the traffic model for local traffic conditions which are easy to use and powerful:

• Standard models and options available for different countries
• Customised Models can be prepared by users
• Realistic model level of detail allows input to match real-life traffic conditions
• Large number of Templates available to represent varying intersection conditions
• Sensitivity analysis facility allows testing the effect of variations in values of key parameters on output
• User Guide describes techniques for local calibration techniques (including survey methods)

HCM Version of SIDRA INTERSECTION
HCM 2010 Roundabout Model Option

SIDRA INTERSECTION User Interface

SIDRA INTERSECTION offers an easy-to-use Microsoft Office 2007 style user interface with enhanced file management, input dialogs, error handling, a detailed input report, numerous output reports and graphical displays and a graphs facility.

VIDEO: SI5.1 USER INTERFACE

Simple Input Preparation

SIDRA INTERSECTION offers graphics-based input dialogs. The intersection geometry and signal phasing data style of SIDRA INTERSECTION reflects the design process directly. Together with the use of Layout and Volume Summary displays for easy checking of data, the graphical data simplify the input preparation task to a great extent, and reduce data errors.

Templates

Use the Templates facility for common intersection layouts help to reduce data preparation time greatly. Over 100 TEMPLATES for roundabouts, signals, sign control and pedestrians are available including all MUTCD roundabout design examples.

Easy Intersection Configuration

SIDRA allows creation of intersection models with ease using time-saving intersection configuration and calibration methods. Pedestrian data are given in dedicated pedestrian input dialogs including enhanced pedestrian timing data. Movement priorities (opposed and opposing movements) are set automatically when diagonal legs, deleted approaches and banned movements are introduced, and when movement type (e.g. slip lane) or control (e.g. major road / stop sign) is changed.

Inspect Output with Ease

SIDRA INTERSECTION output includes capacity, timing and performance results reported for individual lanes, individual movements, movement groupings (such as vehicles and pedestrians), and for the intersection as a whole. Estimates of capacity and performance characteristics (including annual sums) such as delay, queue length, stop rate as well as operating cost, fuel consumption and pollutant emissions are available for all intersection types.

Learning

SIDRA INTERSECTION contains comprehensive help facilities. Extensive documentation (500-page User Guide plus major supporting technical reports and papers) is available.

We have been running highly successful SIDRA INTERSECTION training workshops to help you solve intersection evaluation and design problems effectively and reliably.

Download articles from SIDRA SOLUTIONS website
Learn about SIDRA INTERSECTION training workshops

Model Consistency

SIDRA INTERSECTION ensures model consistency in evaluating alternative intersection treatments. This applies to different types of intersection including signalised intersections, roundabouts, two-way stop and give-way /yield sign-control, all-way stop sign control, single-point urban interchanges, signalised pedestrian crossings and more.

Lane-by-Lane Model

Unique lane-by-lane capacity and performance analysis method is used allowing for exclusive lanes and unequal lane utilisation. This method is superior to approach-based and lane-group models used in other software packages.

Drive-Cycle Model

Vehicle path estimation for drive-cycle (modal analysis) method for prediction of operating cost, fuel consumption, greenhouse gas (CO2) and pollutant (CO, NOX, HC) emissions, and vehicle delay components including stopped delay, acceleration - deceleration delay, queuing delay and geometric delay.

Model Features

Calibrate traffic models for your local conditions. Carry out sensitivity analyses to evaluate the impact of changes on parameters representing intersection geometry and driver behaviour. Analyse oversaturated conditions making use of the time-dependent delay, queue length and stop rate models. Investigate implications of alternative capacity models using advanced model settings.

Defaults System

SIDRA INTERSECTION has an extensive defaults system that covers most input data and traffic model parameters. You can create your own

customised model and edit the default parameters set for your own purposes, e.g. to calibrate some parameters for your local conditions.

Design Life

Carry out a Design Life or Flow Scale analysis to assess impact of normal traffic growth or impact of developments. Allow for different growth rates for individual movements and use options for setting different analysis objectives including the Final Year, Worst Movement Level of Service Target, Worst Lane Level of Service Target, Capacity and Practical Capacity.

Intersection Geometry

Handle intersections with up to 8 legs, each with one-way or two-way traffic, one-lane or multi- lane approaches, and short lanes, slip and continuous bypass lanes and turn bans as relevant. Design intersection geometry including lane use arrangements taking advantage of the unique lane-by-lane analysis method of SIDRA INTERSECTION. Analyse many design alternatives to optimise the intersection geometry. Analyse the impact of intersection flaring through short lanes (turn bays, lanes with parking upstream, and loss of a lane at the exit side). Analyse complicated cases of shared lanes and opposed turns, e.g. permissive and protected phases, slip lanes, turns on red.

Vehicles and Drivers

Analyse effects of heavy vehicles on intersection performance. Use heavy vehicle equivalents for model calibration to allow for very large vehicles in specific traffic streams. Use SIDRA INTERSECTION output on vehicle paths through intersection (negotiation distance, radius and speed) in checking your intersection design. Investigate driver characteristics including driver response time estimates associated with queue discharge. Use this information to calibrate microsimulation models.

Performance Measures

SIDRA INTERSECTION provides a large number of intersection performance measures. Standard performance measures such as delay, queue length and number of stops as well as measures to help with environmental impacts and economic analysis are provided. The performance measures offered by SIDRA INTERSECTION include the following:

• Average delay (stopped delay, queuing delay, geometric delay, control delay): seconds per vehicle, seconds per person
• Total delay (delay rate): veh-hours per hour, person-hours per hour
• Back of queue (average, percentile): vehicles, persons, feet, metres
• Cycle-average queue (average, percentile): vehicles, persons, feet, metres
• Lane blockage probability
• Overflow queue (vehicles)
• Effective stop rate: number of stops per vehicle or per person
• Capacity (veh/h)
• Degree of saturation (v/c ratio): percentage
• Flow ratio (arrival flow / saturation flow ratio)
• Practical spare capacity: percentage
• Queue move-up rate: number of stops per vehicle or per person
• Proportion queued: percentage
• Average travel speed: mph, km/h
• Average running speed: mph, km/h
• Negotiation speed in intersection area: mph, km/h
• Performance Index: a weighted combination of delay, stops and queue length
• Pollutant emissions (CO, HC, NOx, CO2): grams, kg (per hour, per km)
• Fuel consumption: gallons, litres, mpg, L/100km
• Operating COST: Dollars (per hour, per mile or per km)

Performance and level of service results are given at various aggregation levels:

• individual lanes,
• individual movements,
• approaches, and
• intersection.

Performance and level of service results are given for:

• vehicles,
• pedestrians, and
• persons (results for pedestrians and people in vehicles combined).

Level of Service Options

SIDRA INTERSECTION offers a large number of alternative Level of Service (LOS) methods and LOS Target settings to determine acceptable design:

• Delay and Degree of Saturation (v/c ratio) - HCM 2010 Method for vehicles
• Delay - HCM 2000 Method for vehicles
• Delay (SIDRA Method) for pedestrians
• Delay (RTA NSW Method) for vehicles
• Degree of Saturation (SIDRA Method) for vehicles
• Degree of Saturation (ICU Method) for vehicles
• Roundabout LOS options:
  • Same as Signalised Intersections
  • SIDRA Roundabout LOS
  • Same as Sign Control

Unique Set of Results for Each Analysis

As an analytical tool, SIDRA INTERSECTION produces unique deterministic results for a given set of inputs while software packages based on microsimulation generally do not. This applies to the capacity, performance and level of service estimates for each lane, each movement, each approach and the intersection.

Advanced Software for Signal Analysis

SIDRA INTERSECTION is a powerful software package for timing, capacity, performance and level of service analysis of signalised intersections (junctions controlled by traffic lights) including signal coordination effects. It uses an advanced critical movement analysis method allowing for overlap movements and movements with two green periods per cycle.

Traffic Signal Timing

Determine signal timings using fixed-time / pretimed and actuated signal analysis methods for any intersection geometry allowing for simple as well as complex phasing arrangements involving overlap movements. Select one of many cycle time options available. Use advanced signal timing options such as green split priority for coordinated movements, equal and unequal target degrees of saturation, cycle time optimisation for fixed-time / pretimed signals or coordinated actuated signals, and maximum green optimisation for actuated signals.

Signal Model Features

Analyse the effects of turn on red and semi-actuated signals. Make use of features such as undetected movements, dummy movements and phase transition data. Use the graphical input method for easy specification of phasing and timing data including known phase times.

SCATS Control

For intersections running under SCATS control, use fixed-time / pretimed analysis method to emulate equal degree of saturation method used by SCATS for green splits. Make use of SCATS parameter estimates (maximum flow and headway, occupancy time and space time at maximum flow) given by SIDRA INTERSECTION for calibration purposes where applicable.

Cycle Time and Green Split Options
SIDRA INTERSECTION offers different options to specify the desired method of cycle time calculation (subject to minimum and maximum cycle time constraints):

• Practical Cycle Time: A cycle time and green times that satisfy the practical (target) degree of saturation for critical movements are determined.
• Optimum Cycle Time: A cycle time that optimises a selected performance measure is determined for fixed-time pretimed or coordinated actuated signals. One of a large number of options can be chosen as the performance function to determine the best cycle time.
• User-Given Cycle Time: The green times using the given cycle time are determined for fixed-time pretimed or coordinated actuated signals.
• User Given Phase Times: The phase times given for the selected sequence are used. In this case, the phase times are added to determine the cycle time.

The Green Split Priorityoption is available for the allocation of longer green times to coordinated movements while keeping other movements at their target (practical) degree of saturation levels.

Parameters for Actuated Signaltiming analysis include Maximum Green Setting, Gap Setting and Effective Detection Zone Length. Actuated signal timings can be optimised by varying the Maximum Green Settings.

More information on SIDRA INTERSECTION for signals

Emissions and Energy

SIDRA INTERSECTION estimates the cost, energy and pollution implications of your intersection design using a unique vehicle path model (4-mode elemental model with detailed acceleration, deceleration, idling, cruise elements). This drive-cycle (modal analysis) method coupled with a power-based vehicle model helps to estimate operating cost, fuel consumption, greenhouse gas (CO2) and pollutant (CO, NOX, HC) emissions towards reducing environmental impacts of traffic congestion. The model includes estimates of acceleration and deceleration times and distances for light and heavy vehicles coupled with a polynomial model of acceleration-time profile.

The four-mode elemental model used in SIDRA INTERSECTION for fuel consumption and emission estimation includes the following features:

• Fuel consumption, operating cost and pollutant emissions are estimated for each lane of traffic separately.
• In each lane, the model is applied to queued and unqueued vehicles separately according to the proportion queued estimated by SIDRA INTERSECTION. For unqueued vehicles, only the cruise and geometric stop components apply. For queued vehicles, the "drive cycles" are estimated distinguishing between major stops, queue move-ups (stops in queue) and geometric stops (slow-down or full stop in the absence of any other vehicle). These drive cycles are very different for different intersection types (signalised, sign-controlled, roundabout), for different signal phasings (one or two green periods in the cycle), for give-way / yield and stop control, and for different congestion levels.
• If the approach and exit section cruise speeds are different for unqueued through vehicles at traffic signals and priority movements at unsignalised intersections, they are considered to be subject to an acceleration or deceleration during their travel.
• Drive cycles are defined by the initial and final speeds in each element of the driving manoeuvre. Approach and exit cruise speeds, intersection negotiation speeds and queue move-up speeds are used for this purpose. Some of these speeds are specified as input by the user, some are calculated by the program according to the intersection geometry and traffic congestion levels.
• The drive cycle information is used to calculate acceleration and deceleration times and distances for each element of the drive cycle individually. Effective cruise distance, cruise time and idling time are calculated using this information as well as traffic performance estimates (delay, number of stops).
• The fuel consumption, emission rates and operating cost values are calculated for each element of the drive cycle individually. The results are added together for the entire queued vehicle manoeuvre, and then the results for queued and unqueued vehicles are aggregated.
• Fuel consumption and emission rates are calculated from a set of equations which use such vehicle parameters as mass and fuel / emission efficiency rates, as well as road grade and relevant speeds (cruise, initial, final).
• In the above process, light and heavy vehicles are treated separately with different parameters (e.g. different mass, different acceleration and deceleration characteristics).

More information on SIDRA INTERSECTION pollutant emission and energy model

Benefit-Cost Analysis

SIDRA INTERSECTION performance estimates (delay, number of stops, average speed, etc.) can be used as parameters in your economic analysis model, or the operating cost estimates of SIDRA INTERSECTION can be used directly, for Benefit - Cost analysis to evaluate intersection treatments. This is enhanced by the Demand Analysis (Design Life or Flow Scale) facility. Annual Sums for performance statistics such as total delay, total operating cost, total fuel consumption, total CO2 emission per year are also provided for this purpose.

Advanced Software for Roundabouts

SIDRA INTERSECTION is the most popular traffic software for roundabouts and other intersections around the world. Multi-lane roundabouts and single-lane roundabouts with up to 8 legs (each as a two-way road, one-way approach or one-way exit) can be analysed with ease.

SIDRA INTERSECTION offers numerous TEMPLATES for roundabouts including all roundabout examples given in MUTCD 2009 and TRB 2010 Roundabout Informational Guide ( NCHRP Report 672).

More information on SIDRA INTERSECTION for roundabouts

Roundabout Metering Model

SIDRA INTERSECTION offers a unique Roundabout Metering analysis method which enables the evaluation of the effect of metering signals on roundabout capacity and performance with ease. This helps to solve the problem of excessive queuing and delays at approaches affected by unbalanced traffic streams at roundabouts.

Model Calibration

As advanced software for roundabout analysis, SIDRA INTERSECTION provides powerful model calibration facilities. Calibration parameters such as Environment Factor, HCM 2010 roundabout capacity model calibration factors and the Sensitivity Analysis facility can be used to achieve observed capacity values. .

Dynamic Gap-Acceptance Behaviour

SIDRA INTERSECTION uses empirical gap-acceptance models based on data collected at roundabouts in Australia and USA. The critical gap and follow-up headway parameters used in modelling the gap-acceptance behaviour of drivers entering a roundabout depend on roundabout geometry as well as the circulating flow rates. This allows drivers to accept shorter gaps at roundabouts as demand flow rates increase over time. Capacity of roundabout entry lanes also depends on lane balance of circulating flows as well as balance of origin-destination demand patterns.

HCM 2010 and Aditional Capacity Models

SIDRA INTERSECTION offers the HCM 2010 roundabout capacity model based on US research on roundabouts. The model is implemented as described in Highway Capacity Manual 2010 with numerous extensions. The Highway Capacity Manual (HCM) versions of SIDRA INTERSECTION use the HCM 2010 roundabout capacity model as the default model. The software also continues to offer the SIDRA Standard model with a default Environment Factor of 1.2 to match the lower capacity estimates based on US roundabout research.

Detailed information on the HCM 2010 roundabout model in SIDRA INTERSECTION
General information on the HCM Version of SIDRA INTERSECTION

SIDRA INTERSECTION also offers several additional roundabout capacity models for comparison with its main model. These include the FHWA 2000 roundabout model which is similar to the UK TRL linear regression ("empirical" model) used in the UK roundabout software packages (ARCADY and RODEL).

Pedestrian effect on roundabout capacity

Pedestrian effects on roundabout entry lane capacity and exit lane capacity (vehicles giving way to pedestrians on exit) are modelled in SIDRA INTERSECTION. Staged movements are used to correspond to the approach and exit sides of the roundabout leg. Output relevant to the effect of pedestrians at roundabouts is given in output.

Bypass Lanes at Roundabouts.

SIDRA INTERSECTION allows detailed modelling of slip and continuous bypass lanes at roundabouts. Slip lanes can be give-way / yield or stop controlled. Both shared and exclusive slip lanes can be modelled.

The Highway Capacity Manual (HCM) version of SIDRA INTERSECTION offers options for US Customary and Metric units. SIDRA INTERSECTION is compatible with the Highway Capacity Manual. However, unlike other software packages, the HCM version of SIDRA INTERSECTION does not claim to be a simple replication of the HCM procedures. Instead, SIDRA INTERSECTION offers various extensions on the capabilities HCM offers.

Extensions SIDRA INTERSECTION Offers - General

Generally (for all types of intersection), SIDRA INTERSECTION uses more advanced models and methods, including lane-by-laneanalysis (rather than analysis by lane groups), modelling of short lanes, detailed modelling of geometric delays, and the use of drive cycles (cruise, acceleration, deceleration and idling) for detailed modelling of delay and travel time components as well as operating cost, fuel consumption and emission estimation.

SIDRA INTERSECTION includes various configuration options to allow the user to choose between the HCM and standard SIDRA model options, e.g. the HCM Delay and Queue model options.

Some HCM models or methods are used in all versions of SIDRA INTERSECTION, including the HCM Level of Service method and criteria, the delay and queue progression factors for signal coordination effects, and All-Way Stop Control (AWSC) analysis method (the SIDRA AWSC model is currently based on the HCM 1994 edition, and there are some differences between the SIDRA and HCM two-way stop control models).

For signalised intersections, in addition to the general features mentioned above, advanced signal timing methods are available, and the use of two green periods for modeling slip lanes, RTOR and permitted-protected left-turns provides more accurate capacity estimates.

The HCM version of SIDRA INTERSECTION is based on the calibration of most model parameters using the HCM defaults as applicable.

Extensions SIDRA INTERSECTION Offers - ROUNDABOUTS

TRB Highway Capacity Manual 2010 (HCM 2010) has been published recently, and a full implementation of the new roundabout capacity model described in the manual is now available in SIDRA INTERSECTION 5.1. This new version of the software offers powerful extensionsto the HCM 2010 methodology to enhance your roundabout design capabilities.

The roundabout capacity model is the only analysis method in HCM 2010 which uses lane-by-lane analysis, and as such it is best implemented by SIDRA INTERSECTION which has been using a lane-by-lane methodology for all types of intersection since 1980s.

The Highway Capacity Manual (HCM) versions of SIDRA INTERSECTION use the HCM 2010 roundabout capacity model as the default model. It also continues to offer the SIDRA Standard model with a default Environment Factor of 1.2 to match the lower capacity estimates based on US roundabout research.

HCM 2010 acknowledges the need to use alternative models in view of various shortcomings it lists about the HCM 2010 roundabout capacity model. SIDRA INTERSECTION is one of the alternative tools referred to in HCM 2010. The limitations listed in HCM 2010 are addressed by SIDRA INTERSECTION through extensions to the HCM 2010 model option or as part of the SIDRA Standard model option.

Detailed information on major extensions to the capacity and performance estimation method offered by the HCM 2010 roundabout model integration in SIDRA INTERSECTION is given in in the HCM 2010 Roundabout Capacity Model page.

Also see: General Information on the HCM Version of SIDRA INTERSECTION

Modelling Closely-Spaced Intersections

While SIDRA INTERSECTION is a single-intersection analysis software, its model does not assume isolated operations. Thus, it can be used for analysing closely-spaced intersections, pedestrian crossings near intersections, or any number and type of multiple intersections. This applies to both undersaturated and oversaturated cases, i.e. whatever the degrees of saturation (v/c ratios) are. The important aspects of modelling closely-spaced intersections are:

• platooned / bunched arrivals from upstream intersections, and
• blockage of downstream entry lanes.

SIDRA INTERSECTION has the following provisions for multiple intersection analysis as in the case of closely-spaced intersections and network applications.

• Signal coordination effects on signalised intersection performance can be modelled using the Arrival Typeor Proportion Arriving During Greenparameter.
• Upstream signal effects on roundabouts and sign controlled intersections can be modelled using the Extra Bunchingparameter.
• The Capacity Adjustmentparameter can be used to model the amount of capacity reduction for upstream intersection lanes based on the probability of blockage estimated for downstream intersection lanes.

It is important to specify the approach and exit lane lengths and number of lanes (including any approach and exit short lanes) for all intersections realistically, especially for internal approaches between intersections so that queue storage problems can be identified.

Lane underutilisation is an important issue at closely-spaced intersections. Lane flow estimates of SIDRA INTERSECTION should be inspected and lane utilisation specifications should be given if necessary.

CLOSELY-SPACED ROUNDABOUTS and SIGN-CONTROLLED INTERSECTIONS

For platooned arrivals at roundabouts and sign-controlled intersections (due to upstream signals), the Extra Bunchingparameter is used. Platooned arrivals are not as important at roundabouts unless the extra bunching is very high and the proportion queued is very low. This is because roundabout capacity is determined by the circulating flow, and the headway distribution of circulating flow is affected by queues on roundabout approaches which filter out platooning depending on the amount of queuing. All this is modelled by SIDRA INTERSECTION.

The effect of upstream roundabouts or sign-controlled intersections on the arrival pattern at a roundabout or sign-controlled intersection approach is minimal since the departure patterns from upstream unsignalised intersections are randomised due to the gap-acceptance process.

CLOSELY-SPACED SIGNALISED INTERSECTIONS

The following are important steps when using SIDRA INTERSECTION for closely-spaced signalised intersections with signal coordination.

• Run each intersection individually and determine the cycle time. The intersection with the longest cycle time is the critical intersection. Select a system cycle time accordingly, specify this cycle time for each intersection, and re-analyse. Use the green split priority method to favour the internal approaches in green time allocation.
• Nominate internal approach movements as "coordinated" for platooned arrivals, and specify Arrival Typesor Proportion Arriving During Green.
• If queues exceed the available storage spaces, change the signal phasings and timings in order to minimise the queue lengths.
• Alternatively, model the effect of internal approach queues (blockages) on external approach capacities, delay and queues using the Capacity Adjustmentparameter.