Montgomery County officials are instituting new security measures on the county's Ride On bus service to enhance public safety and encourage more vigilance for suspicious activity.

Buses are equipped with silent alarms that can be activated discreetly by drivers and with emergency cell phones for drivers to call 911 directly. A new security hotline -- 240-777-5835 -- is open to take reports of suspicious activity seen on a bus or observed in a neighborhood by someone traveling on a bus.

In making the announcement earlier this week, Montgomery County Executive Douglas M. Duncan (D) said that some of the security measures already were in place but that the efforts have increased since four suicide bomb blasts in London on July 7 killed more than 50 subway and bus passengers.

"It's not something we waited for the London bombing to start doing," Duncan said, citing the 2002 sniper slaying of Ride On driver Conrad Johnson as a reminder of the daily risks that the system's employees and passengers face.

"We live in dangerous times," he added, reminding bus riders to be alert for suspicious activity. The incidents in London, Duncan said later, show that similar attacks "could happen here at any time as well, and we want to be prepared."

The county's top emergency response officials, including Police Chief J. Thomas Manger and Fire Chief Thomas W. Carr Jr., joined Duncan in announcing the enhanced safety measures as well as the addition of new buses.

"We think we do play some part in the success of Ride On," Manger said.

Among the safety measures Ride On has already implemented or is instituting:

* Uniformed and plain-clothes police officers have been riding on buses since January in an attempt to reduce disruptive behavior. These officers can issue citations and arrest passengers who commit serious offenses. Officials also can bar a passenger from using Ride On buses for a period. Police officials said that there have not yet been any arrests and that they think the police presence is discouraging inappropriate behavior on buses.

* Cameras will be installed in all new buses. About half of the Ride On fleet of approximately 360 buses will have cameras on board by the end of June 2006, officials said.

* Bus drivers and administrators continue to get more training, including a course on recognizing potential terrorist activity.

* Security at bus depots has been increased, with facilities now using electronic access for bus entrances and stricter sign-in procedures for visitors.

* Last November, Ride On initiated a campaign to increase awareness among system employees, passengers and area residents. The federal Transit Watch, modeled after the Neighborhood Watch program, also stresses preparation for emergencies and sets up placards and distributes brochures to passengers with tips and instructions on spotting and reporting suspicious behavior.

At this week's news conference, Duncan also announced that Ride On will add 33 buses in fiscal year 2006. The additional vehicles will support expanded service and routes across the county, including areas of the fast growing Route 29 corridor.

Duncan said Ride On served 25.1 million passengers in fiscal 2005, up from 23.2 million the previous year.

Officials said they are on pace to meet the goal set in 2000 of doubling the number of Ride On users by the year 2020.