Exercise NorthStar V is taking place at four subway stations and a bus interchange.
The five exercise locations are Dhoby Ghaut, Toa Payoh, Raffles Place and Marina Bay MRT stations as well as the Toa Payoh Bus Interchange.
The drill started at 6.25am and will last till 9.30am.
While the three-hour exercise is confined to only four MRT stations, however, due to the interconnected nature of the train network, temporary disruption of services will affect a total of 13 train stations.
These 13 stations will be closed throughout the duration of the exercise.
They are namely:
1. Braddell
2. Toa Payoh
3. Novena
4. Newton
5. Orchard
6. Somerset
7. Dhoby Ghaut
8. Clarke Quay
9. City Hall
10. Raffles Place
11. Tanjong Pagar
12. Marina Bay
13. Chinatown
http://www.channelnewsasia.com/stories/singaporelocalnews/view/187107/1/.html