Appendix E 2.1 Input Data
The first step in timing and performance analyses of a signalised intersection is preparation of input data using an intersection layout plan, and signal phasing, design volumes and other information on traffic characteristics at the intersection. The following is a summary of the input data for timing and performance analyses of signalised intersections.
- Intersection configuration (cross-intersection, T-intersection, etc.).
- For each intersection leg:
- two-way, one-way approach or one-way exit
- signalised pedestrian crossings and type (one-stage or two-stage)
- banned movements
- number of approach and exit lanes (at the stop line)
- median width at the stop line if a median strip exists
- approach short lanes (limited queuing space due to turn bays or parking)
- exit short lanes (merging due to reduced number of exit lanes)
- bus only, tram only and bicycle lanes
- details of parking arrangements, bus stops, tram stops, emergency access for each approach lane:
- lane type and control including slip lane (give-way, stop, signalised) and continuous lane
- lane discipline (left turn, through, right turn, exclusive or shared)
- lane width
- grade (negative for downhill, positive for uphill)
- lane (storage) length
- free (non-blocking) queue values for shared lanes
- basic saturation flow
- saturation speed
- number of parking manoeuvres and buses stopping (affecting saturation flow)
- lane utilisation and capacity adjustment.
- Demand volume counts (or estimates) in vehicles per 15 minutes, 30 minutes or 60 minutes, in origin-destination format describing left turn, through, right turn as well as any diagonal or U‑turn movements for each movement class (light vehicles, heavy vehicles, buses, bicycles, etc.).
- Volume data method (separate movement class values, total volume and percentage values for movement classes, or total volume and movement class values in vehicles).
- Volume factors including peak flow factors for peaking effects, flow scales, vehicle occupancy (persons per vehicle) and growth rates for design life analyses.
- Pedestrian volume counts.
Signal control data
- Signal analysis method, i.e. fixed-time or actuated analysis (if the intersection runs under SCATS control, fixed-time analysis is recommended as more appropriate for green split calculations using the equal degree of saturation principle).
- Signal phase sequences to be tested (one or more).
- Phase data (vehicle and pedestrian movements which operate in each phase, yellow times and all-red times).
- Vehicle movement timing data (vehicle start loss and end gain times, minimum and maximum green times).
- Pedestrian movement timing data (pedestrian start loss and end gain times, minimum green and maximum green times, crossing speed, minimum walk time, minimum clearance time, clearance time overlap).
- Phase green times and cycle time if data observed in the field or reported by SCATS or other control system are available (for testing current traffic conditions under current signal timings).
- Cycle time calculation options (practical cycle time, optimum cycle time, user-given cycle time, user-given phase times).
- Green split priority option for allocation of any excess green times in long cycles when a cycle time is specified.
- Signal coordination data (percentage arriving during green or arrival types describing progression quality).
- Left turn on red where applicable.
Movement operational data
- Approach and exit speeds, approach travel distances.
- Negotiation radius, speed and distance for movements through the intersection.
- Queue space, vehicle length.
- Various parameters for saturation flow adjustment including heavy vehicle, turning vehicle and pedestrian effects.
- Movement priorities (opposed and opposing movements) and gap-acceptance parameters for opposed turns (filter right turn and slip lane left turn movements).
- Practical (target) degrees of saturation for signal timing and spare capacity calculations.
SIDRA INTERSECTION provides default values for most input data items, representing commonly occurring conditions, and various calibration facilities including sensitivity analysis. The default values can be used where data are not available. The single most important parameter for calibration of signalised intersection capacity and performance modelling is the saturation flow rate (for further guidance refer to Akcelik & Associates 2011 and Austroads 2017c).
Input data auditing
The intersection Layout and Volume Summary displays help to check input data visually. The Input Report lists all input data to help the analyst to check the input data in table form. A separate INPUT COMPARISON program helps to audit input data including identifying where input data have been specified to replace the default values (refer to Akcelik & Associates 2011).