The Director of the Department of Transportation has provided us with an incident report briefing on the traffic signal problems that occurred on the morning of June 29. The good news is that this incident was not directly related to the failure that we experienced in November 2009 in which the signal computer failed. I've reprinted the report her.
MEMORANDUM
July 1, 2010
TO: Nancy Floreen, President
Montgomery County Council
FROM: Arthur C. Holmes, Jr., Director
Department of Transportation
RE: June 29, 2010 Incident with the County’s Traffic Signal System
The purpose of this memorandum is to provide an incident report briefing with respect to the problems with the County’s traffic signal system that occurred on the morning of June 29, 2010.
At 7:01 AM on the subject date, a fire alarm went off in the traffic signal computer room on the 11th floor of the Executive Office Building (EOB). Fire personnel were on scene by 7:05 AM, and Facilities Maintenance personnel responded by 7:08 AM. At the same time, technicians in the Traffic Management Center (TMC) realized that the traffic signal system stopped operating, and began dispatching personnel to the EOB and the lane control systems on Colesville Road and Georgia Avenue (to manually implement those systems to coincide with static signing that directs drivers to use the AM inbound lane configurations).
By approximately 7:10 AM, the response team had completed their emergency response assessment and had confirmed that there was no fire or smoke in the room. However, as a result of the alarm, all electrical power to the room was automatically shut down and water was confirmed to be pooling under the computer room’s raised floor. The computer room is designed so that when certain critical alarms are activated, such as a smoke detector, the electrical power (both house and emergency power) is immediately and automatically shut down as a failsafe to prevent catastrophic damage to critical equipment. This shut down of the electrical power caused the traffic signal system computer to immediately power down (analogous to pulling the electrical cord from one’s PC from a power outlet).
Facilities Maintenance personnel then began an assessment of the building support systems in the computer room and on the 11th Floor of the EOB and had determined that the source of the water was the dedicated air conditioning (AC) unit. Specifically, the water leak was caused by a failure of the AC unit’s condensation pump. Work immediately commenced to clean up the water, while technicians began troubleshooting the AC unit to stop and repair the leak. Once the leak was stopped, the remaining water was cleaned up and action taken to dry the floor and electrical systems as quickly as possible so that electrical power could be safely restored. Power was restored to the computer room at approximately 9:10 AM, and the signal system was powered back up and all traffic signals in the field were restored to central control by 9:20 AM. In fact, the signal system was restored to operation before the faulty AC unit was fully repaired. Facilities personnel continued working on the AC unit until it was back in service about an hour after the signal computer was restored to operation.
While the traffic signal system was inoperative between 7:00 AM and 9:20 AM, all signalized intersections in the County operated on color, and there were no safety hazards to motorists or pedestrians. The signals operated using their local intersection programming, but there were no coordinated cycle lengths or synchronization that is controlled from the central computer. Traffic management technicians were monitoring traffic flow around the County using the traffic surveillance cameras and our aerial observation capabilities. Using that information, traffic signal technicians were dispatched to selected intersections to manually adjust local signal timings in an attempt to mitigate isolated congestion issues. In general, traffic volumes were lighter than a typical weekday morning commute due to the summer period, although the US 29 corridor was experiencing heavier than usual traffic volumes due to an accident on I-95 in Howard County that caused traffic to divert to US 29.
I want to assure you that the June 29 problem was not a repeat of or directly related to the failure that we experienced in November 2009. The traffic signal computer did not fail. As described above, the issue was related to the building support systems. I have been in communication with David Dise, Director of the Department of General Services, and we will be working cooperatively to assess these support systems and undertake actions as appropriate to minimize the possibility of similar problems. It should be noted that all responding departments (Fire & Rescue, General Services, Police – including both EOB Security and at the ECC) responded as quickly as possible and the incident was handled swiftly and professionally. This situation could not have been resolved more quickly without endangering the very computer equipment the fire suppression system is designed to protect.
On a closing note, I am happy to report to you that not all of the approximately 800 signalized intersections in the County were affected by this issue. Approximately 50 intersections have been converted to the new traffic signal system, and those locations operated without incident or issue. We remain on schedule and within budget to convert all of the remaining signalized intersections to the new system and deactivate the existing system by the summer of 2012.
Please feel free to contact me or Emil Wolanin, Chief of our Traffic Engineering & Operations Division should you have any questions or need additional information.
Arthur Holmes, Jr., Director
Department of Transportation
Montgomery County, Maryland
July 1, 2010
TO: Nancy Floreen, President
Montgomery County Council
FROM: Arthur C. Holmes, Jr., Director
Department of Transportation
RE: June 29, 2010 Incident with the County’s Traffic Signal System
The purpose of this memorandum is to provide an incident report briefing with respect to the problems with the County’s traffic signal system that occurred on the morning of June 29, 2010.
At 7:01 AM on the subject date, a fire alarm went off in the traffic signal computer room on the 11th floor of the Executive Office Building (EOB). Fire personnel were on scene by 7:05 AM, and Facilities Maintenance personnel responded by 7:08 AM. At the same time, technicians in the Traffic Management Center (TMC) realized that the traffic signal system stopped operating, and began dispatching personnel to the EOB and the lane control systems on Colesville Road and Georgia Avenue (to manually implement those systems to coincide with static signing that directs drivers to use the AM inbound lane configurations).
By approximately 7:10 AM, the response team had completed their emergency response assessment and had confirmed that there was no fire or smoke in the room. However, as a result of the alarm, all electrical power to the room was automatically shut down and water was confirmed to be pooling under the computer room’s raised floor. The computer room is designed so that when certain critical alarms are activated, such as a smoke detector, the electrical power (both house and emergency power) is immediately and automatically shut down as a failsafe to prevent catastrophic damage to critical equipment. This shut down of the electrical power caused the traffic signal system computer to immediately power down (analogous to pulling the electrical cord from one’s PC from a power outlet).
Facilities Maintenance personnel then began an assessment of the building support systems in the computer room and on the 11th Floor of the EOB and had determined that the source of the water was the dedicated air conditioning (AC) unit. Specifically, the water leak was caused by a failure of the AC unit’s condensation pump. Work immediately commenced to clean up the water, while technicians began troubleshooting the AC unit to stop and repair the leak. Once the leak was stopped, the remaining water was cleaned up and action taken to dry the floor and electrical systems as quickly as possible so that electrical power could be safely restored. Power was restored to the computer room at approximately 9:10 AM, and the signal system was powered back up and all traffic signals in the field were restored to central control by 9:20 AM. In fact, the signal system was restored to operation before the faulty AC unit was fully repaired. Facilities personnel continued working on the AC unit until it was back in service about an hour after the signal computer was restored to operation.
While the traffic signal system was inoperative between 7:00 AM and 9:20 AM, all signalized intersections in the County operated on color, and there were no safety hazards to motorists or pedestrians. The signals operated using their local intersection programming, but there were no coordinated cycle lengths or synchronization that is controlled from the central computer. Traffic management technicians were monitoring traffic flow around the County using the traffic surveillance cameras and our aerial observation capabilities. Using that information, traffic signal technicians were dispatched to selected intersections to manually adjust local signal timings in an attempt to mitigate isolated congestion issues. In general, traffic volumes were lighter than a typical weekday morning commute due to the summer period, although the US 29 corridor was experiencing heavier than usual traffic volumes due to an accident on I-95 in Howard County that caused traffic to divert to US 29.
I want to assure you that the June 29 problem was not a repeat of or directly related to the failure that we experienced in November 2009. The traffic signal computer did not fail. As described above, the issue was related to the building support systems. I have been in communication with David Dise, Director of the Department of General Services, and we will be working cooperatively to assess these support systems and undertake actions as appropriate to minimize the possibility of similar problems. It should be noted that all responding departments (Fire & Rescue, General Services, Police – including both EOB Security and at the ECC) responded as quickly as possible and the incident was handled swiftly and professionally. This situation could not have been resolved more quickly without endangering the very computer equipment the fire suppression system is designed to protect.
On a closing note, I am happy to report to you that not all of the approximately 800 signalized intersections in the County were affected by this issue. Approximately 50 intersections have been converted to the new traffic signal system, and those locations operated without incident or issue. We remain on schedule and within budget to convert all of the remaining signalized intersections to the new system and deactivate the existing system by the summer of 2012.
Please feel free to contact me or Emil Wolanin, Chief of our Traffic Engineering & Operations Division should you have any questions or need additional information.
Arthur Holmes, Jr., Director
Department of Transportation
Montgomery County, Maryland
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