on 8 january 2006, a large scale emergency preparedness exercise was conducted. codenamed exercise northstar v, it involved 22 agencies and 2,000 emergency personnel. an additional 3,400 commuters also participated in the exercise. the exercise involved a simulated terrorist bomb attack on four mrt stations (raffles place, dhoby ghaut, toa payoh and marina bay) and one bus interchange (toa payoh). there were 500 mock casualties suffering from "injuries" caused by the "explosions" as well as chemical agents. the exercise is the largest civil emergency exercise ever staged in the country.