The Land Transport Authority (LTA) is expected to call a tender for the installation of the next generation of electronic road pricing (ERP) system as early as the first half of next year.
The Straits Times understands the satellite-based system - which can charge motorists for the distance they travel in the priced zones - could be up and running before 2020 if all goes well.
The first phase, however, is likely to merely replicate what the current 15-year-old system does: charging drivers each time they drive past an ERP gantry.
Although there is potential for it to go island-wide, the so-called ERP II system will initially cover the areas marked by today's network of some 70 gantries.
The tender follows an 18-month trial at Woodlands Avenue 12 that concluded a year ago in December 2012. Four teams - Kapsch TrafficCom, MHI Engine System Asia & NCS, ST Electronics (Info-Comm Systems) & IBM Singapore, and Watchdata Technologies & Beijing Watchdata System - took part in the trial, each receiving $1 million in funding.
When asked for an update on ERP II, an LTA spokesman would only say that the authority had tested "the proposed technological solutions" by the four "under different road and environmental conditions... and concluded that a global navigation satellite system-based system is likely to be feasible in Singapore".
Sources close to potential bidders said the system has proven to be technologically sound, but there are issues that need to be addressed.
These include enforcement and privacy. For instance, a motorist entering a priced zone without sufficient funds in his stored-value card today will have a photo of his vehicle captured, with time and location recorded, and a fixed fine is imposed.
But such a method may not be adequate if the system were to charge for distance travelled.
Additional steps may also be necessary to ensure the privacy of users is not compromised.
At a conference held in Tokyo last month, Mitsubishi Heavy Industries - one of the participants of the trial - showcased an in- vehicle unit resembling a navigation set that informs drivers when they are approaching a priced zone.
Although the system is satellite-tracked, and could replace the current blue-and-white ERP gantries that have become a Singapore landmark, observers said it is unlikely to do away with gantries completely.
The trial at Woodlands showed a series of gantries that were slimmer and less obtrusive than those used today.
Transport researcher Lee Der-Horng from the National University of Singapore said: "Since the system will not be island-wide, you need to tell people they are entering a restricted zone... you still need some form of gantry."