Taufik Ramadhan Indrakesuma – For several months now, residents of South Jakarta have been forced to endure road closures and detours because of the Antasari flyover project that aims to connect the Cilandak and Blok M areas.

Now that the project is nearing completion, people are eagerly anticipating an end to all the suffering, and looking forward to the promised payoff of less-congested roads and quicker commutes. That, of course, is the story that the Jakarta government is selling.

Unfortunately, all the hardship has been for nothing. Well, not nothing, but the actual benefits will be so miniscule that that's what they'll seem like.

The reason is simple, although it involves fancy-sounding terms like "induced demand" and "triple convergence theory." To put it simply, it is a problem of incentives: If more roads are built, then there's more incentive to drive. More people will drive, and people will drive more.

The policy's logic does seem intuitive: given a fixed number of vehicles that pass through the Antasari corridor, any expansion of roads there will result in a lower density of vehicles on those roads, which means less congestion. This is true initially. During the first week or two that the new flyover is operational, congestion will improve substantially because of the additional lanes.

Beyond that point, however, the logic fails because the number of cars is not fixed. There is a subset of the population that has the option to drive a car to work but chooses not to because the heavy congestion makes them prefer other modes such as carpooling or taking the bus. However, once they perceive that road conditions have improved, they will want to start driving again. This is called induced demand, which is when demand increases in response to a raised supply.

The problems don't stop there. Triple convergence theory, developed by Anthony Downs in 1992, theorizes that there are more consequences to road expansion. People switching from public to private transportation is only one element of the triple convergence.

The second element concerns people who previously used alternative, less-convenient routes. Now that the main road is expanded, they will no longer take a detour. Let's say there are some people who would prefer Antasari but use the Fatmawati corridor instead because of the congestion on Antasari. After the flyover is complete and the initial impact becomes apparent, these people will flock to Antasari, their preferred route.

The third element consists of people who previously avoided peak-hour travel through Antasari because of congestion during that time, choosing instead to travel extra early to work, or extra late back home. Again, because the congestion appears to subside after the road expansion, more people will travel at peak times.

There have been many instances of failed road expansion in the Greater Jakarta area. Despite the number of lanes the city has added to its arterial roads, the traffic problem hasn't gone away. Unfortunately, however, road expansion is still an integral part of Jakarta's recently drafted spatial master plan for 2010-30, so one can only assume the city will keep doing it, over and over again.

If road expansion ultimately just doesn't work as a traffic management tool, why is it still happening? Let's put aside, for now, any suspicions that governments prefer big, corruption-prone infrastructure projects and assume them to be relatively honest. Besides road expansion, there is a range of traffic-management policies available. Better public transportation, higher taxes for automobiles, higher fuel prices, higher parking fees and congestion charges are all tools the Jakarta government has flirted with at some point. Some of them are part of the spatial master plan and some, such as the electronic road pricing congestion charge, are close to becoming reality.

All of those policies have one thing in common: they are disincentives to drive. And here's the problem with driving disincentives: people hate them. No one likes the idea of paying Rp 10,000 ($1.14) for one hour of parking or one liter of gasoline. What makes these policies so effective is exactly what causes such backlash against them.

Opposition to driving disincentives also comes from the automotive industry, which, for obvious reasons, hates the idea of reducing demand for cars. Thus, it is a constant uphill battle for policy makers to push demand management policies.

Considering all of that, one might wonder why the government doesn't just do nothing, rather than flush money down the toilet by pouring it into pointless road expansion. Unfortunately, the government doesn't have that option, because doing nothing would get it slammed for inactivity and an inability to respond to Jakarta's worsening traffic crisis. So when something needs to be done and the best options are too difficult to push through, all that's left to do is go forward with road expansion.

Regarding the Antasari flyover, here's a crazy idea that just might help it achieve the its intended purpose of alleviating congestion: turn it into a bus-only lane. No need for TransJakarta to get involved, as there are plenty of Kopaja and Metromini buses that pass through the corridor. Why not make it so these buses can reach their destination 20 minutes quicker than private cars? Maybe then more people will switch to public transportation, and the residents of South Jakarta can finally get some relief. After all, it's all about incentives.

[Taufik Ramadhan Indrakesuma is a research associate at the Lee Kuan Yew School of Public Policy in Singapore.]