Yesterday CashCard issuer Nets said faulty IUs could be the reason some drivers have been penalised at gantries despite having enough money on their cards.

The comments came three days after the Land Transport Authority (LTA) suggested problem CashCards could be behind the glitches.

The debate started last month. Motorists had discovered that Electronic Road Pricing gantries did not deduct money from their CashCards as they drove through, even though they had enough credit.

For weeks, the LTA and Nets both referred the problem to the other. The debate even made its way to Parliament on May 26.

Finally, on May 28, both the LTA and Nets came together to open nine centres where motorists experiencing problems could test their CashCards and IUs. The LTA said nine in 10 cars had CashCards from the 'blue butterfly' batch, and all of them did not have the word 'Gemplus' on the chip.

Over 170 cars were tested and mechanics found no other links.

In response, Nets sent an e-mail to The Straits Times yesterday, saying the supposedly faulty CashCards worked in other electronic devices.

'This points to a compatibility issue between some Nets CashCards and some IUs on the road,' it said.

'Besides the card, we believe, there are many other possible reasons that could cause incompatibility issues. These may include the engineering, the position, age and the wear-and-tear of IUs.'

The Straits Times spoke with eight motorists who experienced glitches. All said that while the gantries or IUs could not detect their CashCards, the cards still worked in ATMs and other devices.

Banker Brandon Huang, 28, was one of those drivers. 'After I realised the CashCards did not work with ERP gantries, I used them for other things like paying library fines...or buying groceries at 7-Eleven. They worked fine,' he said.

The final answer might come a couple of weeks from now when Nets and the LTA are expected to wrap up their investigations.

Even then, it might not be cost-effective to fix the problems, according to industry sources. The glitches happen in a mere 0.003 per cent of the nine million ERP transactions a month.

All this is little consolation for motorists like IT consultant Surendra Halgeri, 56, who said: 'I've gone through this problem nine times, and it's still not resolved. '

tanwz@sph.com.sg

ADDITIONAL REPORTING BY LIM WEI CHEAN