Why is there so much traffic on city roads and highways?

Road space is a scarce commodity, and in most Indian cities, drivers pay nothing to use it. A driver in an Alto uses far less of that space than a driver in an Innova, and both use far less than a mini-truck driver, yet all three pay the same price: zero.

Every car buyer receives more than an engine and a chassis. The purchase also hands the buyer a claim on road space, and nobody prices that claim. Each time an owner drives the car out or parks it, she draws on public space along with the comfort and utility the car provides.

No amount of road-building changes the underlying arithmetic. Road space will always fall short of the number of cars and other motorised vehicles competing for it.

Congestion is what that shortage feels like on the ground. Drivers face longer wait times, more choke points, and speeds that fall well below what the road was built for. The cost runs high: commuters in Bengaluru lose about 168 hours a year to rush-hour traffic, and the TomTom Traffic Index ranks it the world’s second most congested city. Four Indian cities, Bengaluru, Pune, Delhi, and Mumbai, appear among the world’s 25 most congested.

Pricing road space is the only real solution to congestion, and pricing takes several forms. A toll charges drivers simply for access to a stretch of road. Congestion pricing goes further, setting a different price for different times of day through dynamic models. Fast lanes carve out a strip of the existing road that drivers can pay to use for faster transit.

The deeper solution, though, asks two different questions: how should people move from one place to another, and why must so many of them travel such large distances at all?

Public transport answers the first question by freeing up a transformative amount of road space. A passenger on a bus or train needs only the space of a seat or a patch of standing room, far less than a car requires. Public transport moves people with comfort and convenience, just as a car does, and that comparison does much of the work of persuading drivers to give up their cars. Once road space stops falling short of demand, public transport can move people over long distances faster than cars can today. The possibilities run wide: water metros, underground transit systems, trams, and double-decker buses built like ships stacked deck upon deck. Reaching that kind of network takes coordination, political will, and lifestyle changes that are hard to make, but a city that makes them can transform how its people move and live.

The second question asks why people commute such long distances in the first place. Why do so many residents live in Noida but work in Hauz Khas? Housing in Hauz Khas costs far more and sits far scarcer than housing in Noida. A city with more diverse neighbourhoods might persuade an employer to move where its staff live, or persuade staff to live nearer their work. That logic has produced the fifteen-minute city, a model built so that residents can reach any essential service or workplace within a fifteen-minute walk. Some residents will always prefer to cross town for a particular team or a particular restaurant. Still, those residents remain the exception, not the rule, for most of a city’s population. This vision offers the largest possible answer to congestion, among several others, though building it demands a leap of faith from planners and residents alike. The root cause of traffic jams remains the same throughout: a mismatch between the supply of road space and the demand for it, and that mismatch will only worsen, however much space cities add, until they price it.