inside what s known as the bunker, the underground high-tech control room where kurt schwartz, director of the state s emergency management agency, showed us around. more than 100 newly installed cameras along the 26.2-mile route will be monitored, twice as many as last year. we have expanded across the board. reporter: last year, surveillance cameras helped to pinpoint the alleged bombers but only days after the attack. the challenge this year is to stop any possible attack before it happens. anything of trouble, any person that s presenting a concern to us, may be monitored very quickly. reporter: in addition to the cameras, some 4,000 police officers will be on patrol along the route. 500 of them will be undercover in an effort to keep the festive spirit from being overwhelmed by the police. i don t want it to be an armed camp, that people feel intimidated by the police presence. reporter: boston s new police commissioner, bill evans, a runner himself who was in last