RECENTLY, the Land Transport Authority (LTA) announced that a new Electronic Road Pricing (ERP) gantry on the westbound Pan-Island Expressway (PIE) before Eunos Link will be operational with a charge of $2 from 7am to 8am. It has set a target speed of 45kmh and identified that slow traffic in the morning is due to cars and heavy vehicles making short trips from Simei to Paya Lebar.

I am a regular user of this stretch of the PIE from 7am to 8am to travel from Tampines to Jurong for work. I have made these observations:

• For the past week, I have not experienced a slowdown in traffic speed to less than 50kmh on this stretch of the PIE.
• I use the Simei exit on the PIE and do not see a high volume of traffic from Simei before the intended Eunos Link ERP gantry, except when there is an accident or wet weather.
• Bedok is the most densely populated town in Singapore and most vehicles come onto the PIE from the Bedok/Bedok North exit. Even so, there is no traffic slowdown from 7am to 8am, except when there is an accident.

As a road user, I am affected by only two variations - cost of using the road and speed of travel. The present speed is acceptable, but not the cost after the ERP gantry is operational. Hence if the objective is to address our needs, can the LTA share with the public:

• How it concludes that the travel speed should be 45kmh and above for a road user like me to be satisfied?
• What is the sampling plan (number of data points, day of sampling, number of observers) it used to conclude that the traffic speed along this stretch of road is below 45kmh consistently? If it is below 45kmh, how many days of the week is it so?
• Is the sample enough to conclude that traffic from Simei is a significant factor that slows down traffic to 45kmh but not traffic from Bedok? If Bedok traffic is a significant factor, then a gantry before the Bedok exit to the PIE should suffice, given that the objective is to lower the volume of traffic entering the PIE.

Finally, the LTA chose to open the new gantry at a time when many schoolchildren need not report to school. If it wants to use the data to justify that the traffic speed is higher than 45kmh after the new gantry is operational, the data will probably be skewed in its favour.

Lee Chee Seng

This article was first published in The Straits Times on Nov 3, 2008.

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