ERA agent Leong Yoke Keng got a few minutes more of sleep and saved $3 in Electronic Road Pricing (ERP) charges on Monday morning - all because her company let her start 15 minutes later.

She pays $2 for driving down the Central Expressway before 9am and would have to fork out another $1 when she crosses a new ERP gantry.

Her property company, however, is allowing employees a later start at work so that they can save $1 in ERP charges now that a new gantry at Toa Payoh Lorong 6 is in operation.

The Toa Payoh gantry was one of the five new gantries which started operations on Monday in a bid to seal more of the outer cordon of the Central Business District.

Also in operation only in the mornings, the other new gantries are at Upper Boon Keng Road, Upper Bukit Timah, Kallang Bahru and Geylang Bahru and all charge motorists $1.

Traffic in the Upper Boon Keng and Kallang Bahru area remained relatively the same on Monday morning, observed a Straits Times team.

On both roads, traffic was light during the ERP charging periods, and this reporter was able to drive between 40kmh and 50kmh - the same as last week before the gantries were in operation.

Over at Upper Bukit Timah, traffic remained relatively heavy between 8am and 8.30am, an indication that motorists were willing to pay that extra $1.

ERP, introduced in 1998, aims to control congestion by charging drivers for the use of busy roads and getting them to use public transport.

The five new gantries bring the total to 60. Another 11 will come up before November.

The Land Transport Authority says those affected can use premium bus services costing between $2.5 and $7 per morning trip into the city.