Transport planning

Transport planning estimates how many people and goods will travel, where, when and by which mode, so that roads, railways and public transport can be sized and prioritised. The classic method is the four-step model, built on a city divided into traffic analysis zones.

Trip generation estimates how many trips each zone produces and attracts, from population, households, jobs and land use, often by regression from household surveys. Trip distribution links productions and attractions between zone pairs; the gravity model assumes trips between two zones grow with their activity and fall with the cost or distance of travel between them. Mode choice splits trips among car, two-wheeler, bus, metro, walking and cycling, usually with logit models based on time, cost and comfort. Assignment loads trips onto the network, with congestion making travellers spread across routes.

Models are calibrated against counts and surveys and then used to test schemes and future land use. Their limits matter: forecasts depend on assumptions, and building road capacity can induce new traffic. Modern planning therefore pairs models with goals such as access to jobs, safety, emissions and equity, and with land use that reduces the need to travel.

In India, comprehensive mobility plans for cities set out these analyses and proposals, emphasising public transport, walking and cycling.