The Electronic Road Pricing (ERP) scheme was conceived as a means to regulate the use of roads and manage traffic conditions in Singapore. This objective is achieved by drivers paying tolls when traffic is heavier than usual. In order to not cause more problems than it solves, the ERP system does not require the use of toll booths; instead, payments are deducted wirelessly without any further action required from drivers.

As a testament to its robustness, the ERP system has been substantially expanded to a network consisting of more than 80 distinctive gantries (which are road signs) since it was first implemented in 1998.

How it works

There are two components that make the ERP system work. The first is an In-Vehicle Unit (IU) affixed to the front windscreen on the driver’s side. The original IU accepts the CashCard stored value card, while a second-generation “dual-mode” IU adds support for a couple of stored value cards such as contactless cards, for example the NETS FlashPay Card (PDF) and the EZ-Link card for the deduction of a payment.

Second, each ERP gantry (Figure A) consists of two sets of sensors: A dedicated short-range wireless system to communicate with the IU, and cameras that are used to capture (if necessary) the rear license plates of vehicle as they pass by. The cameras allow the authorities to identify the drivers in situations of insufficient funds in the stored payment card or an absent stored value card. A letter demanding payment is sent out to the registered owner of the vehicle caught on camera not paying the toll.

ERP gantry in Singapore (Photo credit: Land Transport Authority of Singapore)

A spin-off project

The presence of an IU in all Singapore-registered vehicles has resulted in a lightweight version of the same technology being deployed in parking lots to pay for parking fees. Known as the Electronic Parking System (EPS), the technology is in almost all private parking and many public parking lots across the nation. If there is interest, I’ll further explore how EPS works and how system integrators deploy them.