There is a very delicate mathematically-determined balance between public transport and private transport.
By Ravi VS Prasad
It is excellent that Delhi CM Arvind Kejriwal has announced that roads in the national capital would be redesigned to minimise traffic congestion (FE, Oct 18).
Kejriwal announced that in the first phase, 45km along nine roads would be redesigned, at a cost of `8-10 crores per km.
But, one must be aware that all “common-sensical” ideas about urban road design are wrong. Sometimes, building more bypasses and flyovers and bridges actually increases traffic congestion. This is termed the ‘Braess Paradox’.
In the 1960s, this was empirically observed in Germany and South Korea. And, it was observed in Manhattan, that sometimes, shutting down connecting roads actually speeded up traffic flows .
Dietrich Braess, a mathematician at Ruhr University in Germany, came up with an explanation in 1968 based on Game Theory, of why building connecting roads and bypasses sometimes increased average commuting times. Every commuter tries to optimise his commute in terms of transit time, cost, and convenience. But attempts at optimisation by each individual do not necessarily result in optimum solutions for the community as a whole.
In 1990, two British traffic experts, Martin JH Mogridge and David Lewis, found that as more roads were built in southern England, more traffic emerged to congest these new roads. They formulated an engineering model called the Lewis-Mogridge Position, stating: “Speed gains from some new roads can disappear within weeks. Sometimes, new roads help to reduce traffic jams, but in most cases, the congestion is only shifted to another junction”.
This can be seen in the instances of the Barapulla, Dhaula Kuan flyover, the Noida DND and the NH8 (Mahipalpur-Gurugram).
In recent years, leading international traffic researchers, such as Anthony Downs, John Michael Thomson, Arthur Cecil Pigou, and Frank Knight, found that: “Improvements in the road network can make congestion worse if the improvements make public transport more inconvenient…. The equilibrium speed of car traffic on a road network is determined by the average door-to-door speed of equivalent journeys taken by public transport…”
In Indian cities, this means that the equilibrium speed across the city is determined by the time it would take to complete the identical route door to door using public transport solely.
Google maps and Twitter updates and broadcasts of traffic conditions on FM Radio often make traffic congestion worse.
Similar to Parkinson’s Law in Management, that work expands to fill the time available for its completion, Anthony Downs formulated the “Iron Law of Traffic Congestion”, that “traffic expands to meet the road space available”. This was observed in Australia and New Zealand.
But heavy dependence on public transport alone can be counterproductive, as has been observed in Japan, where commuter trains are overcrowded, while roads are empty. In Delhi, bottlenecks are starting to develop around the metro stations, especially the parking lots.
It is excellent that the Kejriwal government and Uber have together recognised that there needs to be an integrated transport policy combining public and private transport in an optimum manner, and that the bottlenecks are often in the “Last Mile”. The Public Transport option on the Uber app will display the fastest and cheapest routes.
In fact, insights into avoiding traffic congestion can come from studying ants. Scientists at the University of Toulouse and the University of Arizona and University of Adelaide found: “Traffic jams are ubiquitous in human society where individuals are pursuing their own personal objectives…That’s one reason why just widening highways doesn’t reduce human traffic congestion—there’s an inherent conflict of interest between what benefits us personally and what benefits us collectively, so the result is 30% longer commute times…”
Studying movements of vehicles and humans walking and ants across bridges, the researchers concluded: When humans are walking or driving, the flow of traffic usually begins to slow when the bridge occupancy reaches 40%. Ants, on the other hand, show no signs of slowing, even when the bridge occupancy reached 80%. Individual ants quickly adjusted their behaviour in a manner designed to benefit all the ants as a whole.
There is a very delicate mathematically-determined balance between public transport and private transport. Blindly building more connecting roads, bypasses, and flyovers in the naïve belief that these will ease traffic congestion, only serves to make a few selected contractors very rich.
Actual traffic patterns in Indian conditions need to be measured accurately, and then proposed roads, metro routes, and bus routes need to be carefully modelled and simulated on supercomputers, before these roads and flyovers are actually built or remodelled.
The very same solution which might be brilliantly successful along the Ring Road from AIIMS to Ashram (included in Kejriwal’s first phase) might turn out to be a total disaster along the Ring Road stretch from Naraina to Pitampura. The terrible experience of the BRT in South Delhi ought to serve as a warning.
Traffic infrastructure design is a subject which should be left to experts, without interference by lay-people like politicians and bureaucrats. The expertise to perform such modelling exists in the Indian Institutes of Technology and some institutes specialising in urban planning. Contractors keep exerting pressure to build more flyovers and add buses, which might not necessarily ease traffic congestion, as might be naively believed by the public.
The writer is an alumnus of Carnegie Mellon University and IIT-Kanpur.