I REFER to your article 'Beware of GPS - you're being watched' by Lee Han Shih (BT, Sept 24).
The article noted that 'the movement of a great proportion of vehicles is monitored by the ERP system'.
The article goes on to imply that the system could possibly blanket the island and be used to track the movement of vehicles.
We wish to point out that this is inaccurate.
The Electronic Road Pricing (ERP) system is a critical component of our traffic management strategy and not, as the article implies, a tracking mechanism.
It is an efficient and versatile system to manage congestion by adjusting the cost of using popular roads during peak hours.
Together with the vehicle ownership management measures, it helps to minimise congestion on our roads and keeps them relatively free-flowing.
Please allow me to explain how the ERP system works. There are three components of the system, namely: the In-vehicle Unit (IU) with a stored value CashCard, the overhead gantry and the central computer system.
When a vehicle fitted with an IU approaches the ERP gantry, the first set of antennae on the gantry will communicate with the IU to determine its validity and the appropriate ERP charge based on the vehicle class, and instruct the IU to deduct this charge from the CashCard inserted in the IU.
The status of the deduction is then confirmed by the second set of antennae.
If there is a violation or when the CashCard cannot be deducted due to technical faults, the enforcement camera on the gantry will be triggered to capture a digital image of the rear licence plate of the vehicle once it is detected by the vehicle presence detectors.
The local controller then sends back all the ERP transaction data and digital images to the control centre.
The transaction records are used as a basis to claim the collected ERP charges from the CashCard operator.
These records are automatically deleted from the system once payment from the CashCard operator is received.
As can be seen, the ERP system is used solely as a traffic management tool, and is in no way used by the authorities to track the movement of vehicles.
Eileen Tan (Ms)
Assistant Manager
Media Relations
Land Transport Authority