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ERP is a key pillar of Singapore’s traffic demand management strategy. It serves as an effective tool to manage traffic congestion by internalising the external costs of driving, which includes the impact on other road users. In doing so, motorists are more aware of the true costs of driving.

Road pricing was first implemented in the form of the Area Licensing System in 1975, which levied a flat charge on all vehicles entering the Central Business District (CBD). In 1998, this was replaced by the ERP system, which leverages on technology to allow for a more effective and flexible method of congestion charging.

The Radio Frequency Identification (RFID) technology used also allows an automatic deduction of congestion charge on any vehicle passing under a road pricing gantry during its operating hours. As charges are levied on a per-pass basis, motorists are more aware of the true cost of using their vehicles.

Purpose & Effectiveness

The ERP system provides a targeted solution for congestion pricing. It allows us to pinpoint specific congested spots and vary the congestion charge and operating hours according to prevailing traffic conditions. Therefore, the charges can either increase or decrease according to the demand of usage of the priced-road or expressway, which is reviewed quarterly.

By pricing congested stretches, the ERP system helps to moderate vehicle usage and optimises the road network by encouraging motorists to consider switching their time, route or mode of travel.

Since its introduction, the ERP system has been effective in managing traffic congestion and keeping traffic speeds within the optimal range. However, it has to continue working in tandem with vehicle ownership control measures, road capacity optimisation and increasing public transport use to maintain smooth-flowing traffic.

Traffic Measurement Method

Since July 2008, LTA has applied the 85th percentile speed measurement method instead of average (mean) speeds to determine whether ERP rate changes are necessary.

The lower threshold speeds that trigger ERP rate changes are 45 km/h on expressways and 20 km/h on arterial roads, based on an NTU speed-flow study. However, these limits can cause traffic to easily slip into the unstable zone, where “stop-start” conditions become common. To create a buffer, LTA decided to use a more representative method of measuring actual traffic conditions for ERP rate reviews, with speeds determined using the 85th percentile method. The 85th percentile speed method is an international traffic engineering practice for assessing traffic conditions. With the revised speed method, 85% of motorists will experience speeds above the threshold.

Next-Generation ERP System

As travel demand and congestion grow over time, the ERP system must be continually reviewed to ensure that it continues to help Singapore manage congestion effectively. While the current ERP technology has served Singapore well, we need to look ahead to find a more effective and responsive system of congestion management. It needs to be less costly, more space-efficient and require a shorter lead time to implement compared to the current gantry-based system.

The next-generation ERP system makes use of advanced technologies to provide more flexibility in managing traffic congestion. It will also enable LTA and its industry partners to develop value-added services for the benefit of motorists, such as traffic advisories, via the new On-Board Unit (OBU) that will replace the existing In-Vehicle Unit (IU).