THE introduction of Electronic Road Pricing (ERP) in the heartland may have been announced only on Thursday, but the idea itself is not new.

In fact, the Land Transport Authority (LTA) announced the plan in ERP Phase II in 1999 - a year after ERP was implemented.

Back then, it envisaged average speeds during peak hours on several main roads would fall to as low as 15kmh by 2005. That is slightly faster than jogging pace.

To prevent that, the LTA identified close to 20 sites where gantries would go up. It erected seven in September 1999 and said the rest would probably go up in March 2000.

Apart from one or two locations, gantries in most of the other proposed sites - in Toa Payoh, Kallang Bahru and Upper Boon Keng - were never built.

Until now.

The LTA said on Thursday that seven will be erected by early next year (inclusive of two on the new Kallang-Paya Lebar Expressway). The rest, in towns like Bukit Merah and Telok Blangah, will go up later.

These gantries are not designed to alleviate jams on these "heartland" roads. Rather, they form an outer cordon that seals off non-expressway routes into the city.

The idea is to prevent the city from being congested by traffic arriving via non-ERP roads.

When all the "heartland" gantries are up, there will be a total of 68. This compares to just 35 in 1998 when ERP was introduced.

This may sound like a lot, but it is quite a measured rise over a decade - commensurate with the increase in vehicle population.

From 1998 to July this year, Singapore's vehicle population grew 22per cent to around 830,000. This has contributed to more private transport usage.

In 1997, motorists (drivers and motorcyclists) made 2.74million trips a day, accounting for 37per cent of all motorised trips. In 2004, they made 3.44million trips, or 42per cent of all trips.

These figures might suggest to some that ERP has not been effective, since people have been making greater use of their cars and motorcycles despite the gradual expansion of the scheme and the rise in its rates.

But on the flipside, our roads have remained relatively free-flowing despite the growth in population, denser urban development and the rise in vehicle numbers.

Average speeds on the expressways during peak hours have remained above 60kmh, while average speeds in the Central Business District have remained above 25kmh - the same as on other arterial roads (and double the average in downtown Tokyo).

So it seems that ERP has allowed more Singaporeans to have cars and use them more regularly.

In land-scarce Singapore, it is obvious this dichotomy won't last forever. In future, motorists should be prepared to pay more for the privilege of driving a car.

But ERP alone is unlikely to make driving a financial burden for most motorists. After all, cars have become a lot cheaper over the last decade. For instance, the ubiquitous Toyota Corolla has fallen from $130,000 in the mid-1990s to below $60,000 today. And China cars start from around $30,000.

ERP charges will have to be quite hefty - possibly an average of $15 a day - to persuade people to find alternatives to driving.