Quantifying transit resources and its network-wide temporal distribution is needed for the informed transit planning and operations decisions. In literature, Supply Index (SI) is modelled considering the transit services allocated to a zone and ignores the quality and quantity of the supply provided between two zones. Addressing this need, we propose an origin‑destination based supply index (odSI) that yields valuable insights on the supply provided for the transit mobility between different zones on the network.
We define odSI as the quantity and quality of PT resources provided to a zone while travelling from one zone to another.
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The proposed odSI formulation incorporates a) zonal characteristics such as transit routes operate in origin zone, number of trips made by those routes in the analysis period, walk buffer areas of transit stops (number of transit stops), and the total area of the zone; b) the quality of the service provided in terms of the average speed of the transit services and their route straightness ratio; and c) origin-destination dependent variables such as the minimum number of transfers needed to travel from the origin zone to the destination zone, the average transit speed between those zones, straightness of transit routes, and total available capacity.
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As the proof-of-the-concept, the odSI model is applied on the real network from Brisbane, Australia at Statistical Area-2 (SA2) level with 136 zones. Here, we have used real Google Transit Feed Specifications (GTFS) data from Translink and the Geographical boundaries from the Australian Bureau of Statistics. The interactive tool below presents the odSI results for 136*135 zonal pairs for four different time periods (morning peak, business hours, evening peak, off peak).
Click on the origin zone on the first map and the corresponding odSI for different SA destinations at four different time intervals from a normal working day are presented on the maps below.
Note: The odSI scales are different for the different time intervals.