Improve management and operational procedures during a natural disaster by extending and supporting communication systems and networks.
A Texas Department of Transportation (TxDOT) experience with Tropical Storm Allison's effect on the Houston Metropolitan Transportation system.
Made Public Date


United States

Intelligent Transportation Systems and Tropical Storm Allison: Lessons Learned


On June 4, 2001, Tropical Storm Allison caused widespread flooding and damage in the Houston, TX, metropolitan region. Houston TranStar, a transportation management center that houses a consortium of four agencies -- TxDOT, the City of Houston, Harris County, and the Metropolitan Transit Authority of Harris County -- was responsible for providing transportation and emergency management services to the greater Houston area during the hurricane. Subsequently, the Texas Department of Transportation (TxDOT) commissioned an in-depth review of the operational response. Critical lessons learned were documented.

During peak of the storm, 26 inches of rain fell during one 24-hour period, and 34 inches was recorded in that week. The impact on Houston's Transportation System was severe; all major highways were closed and total damages amounted to $5 million. There was $1 million in roadway damage alone. Additionally, the flooding caused $3 million in damages to ITS and communication facilities. By June 9th, operational rates for Closed Circuit Television (CCTV) and dynamic message signs (DMS) had been reduced by 55.6 percent and 23.8 percent respectively.

Considering the scale of the flooding, Houston TranStar reacted well, continuing to function while several other government agencies and private organizations became non-operational.

Lessons Learned

Increasingly, erratic and severe weather is affecting many parts of the United States. While Houston has often experienced significant thunderstorms, as well as the occasional hurricane, a record amount of rain fell in a very short time during Tropical Storm Allison. Seeking lessons for the future, Houston TranStar's response to the impacts of Tropical Storm Allison was carefully evaluated. The evaluation highlighted lessons learned for both short term changes and long-range goals. Key recommendations involve enhancing TranStar's communication systems to improve the flow of information and to increase redundancy of the system.

  • Design hardware installations that take into consideration all possible weather events. The TranStar system is based on communicating data from ITS equipment in the field to satellite buildings and then to TranStar. Currently, most satellite and hub buildings are located under overpasses to protect them from sun exposure; however, these locations are prone to flooding. During Tropical Storm Allison, for example, key field communications hubs were flooded, causing TranStar to lose communications with approximately two-thirds of the freeway field devices. This experience indicates that when installing new hardware TxDOT must take into account the location of the 100-year flood plain. Hardware installations must also be built to withstand weather extremes.
  • Increase communications capacity to provide information to the public and support a redundant and robust communications system that is tolerant to equipment failure. During Tropical Storm Allison, TranStar operations personnel received an estimated 400 telephone calls per hour and the two TranStar Internet sites were inundated with Web traffic. This demonstrates that the public will try to access as much information as possible in an emergency, using radio, Internet, telephone and other means. Consequently, TxDOT needed to upgrade the capacity of their Web servers to handle the increased demand that a major emergency event creates.
  • Ensure that the roles of agencies are clearly defined and proper emergency preparation procedures are in place, especially if the event occurs during off-peak hours. Flooding from Tropical Storm Allison hit after hours and after maintenance staff had dispersed for the weekend. It was difficult to bring staff back to work to respond during the event because weather conditions were severe. TxDOT learned that, to respond properly to an event such as a tropical storm, adequate notice is necessary to make the appropriate preparations for maximum effective response. There was also some confusion among agencies as to the exact role of TxDOT personnel during a flood event. TxDOT learned that it needed to communicate its role during emergencies to other local agencies.
  • Implement a 511 system for traveler information. This allows the public to obtain information through an automated system via telephone. The contents of a 511 call could include:
    • Construction/maintenance projects
    • Road closures
    • Major delays
    • Weather forecasts
    • Road surface conditions
  • Consider deploying an Asynchronous Transfer Mode (ATM)-based communication system. This will maximize fiber availability through better management of the communications system, resulting in fewer unused fibers and more redundancy. Additionally ATM will support remote resetting of equipment and access to streaming video over the Internet.

This lesson presents some ways in which metropolitan agencies can improve their response to natural and man-made disasters. Specific suggestions include implementing a 511 system for traveler information and considering implementing an Asynchronous Transfer Mode (ATM)-based communication system.

TranStar's experience with Tropical Storm Allison reminds decision makers that it is important to take into account all possible natural conditions when installing hardware. Further, agencies can adapt better to the challenges posed by extreme weather events if they increase capacity and connectivity of communications systems. The Houston experience also highlights the importance of being able to locate and bring in staff when a disaster occurs during off-peak hours.