Intelligent transportation systems and tropical storm Allison: Lessons learned

Intelligent transportation systems and tropical storm Allison: Lessons learned

Wegmann, Sally G



Tropical Storm Allison poured record volumes of rainfall on the Houston, TX, USA, metropolitan region during the week commencing June 4, 2001. The peak 24-hour rainfall total was 26 inches; the recorded cumulative weekly total was 34 inches. The most severe flooding began on the evening of Friday, June 8 and continued through the morning of Saturday, June 9. The rain fell on saturated soil and ran off into local bayous. Nine bayous reached record levels while seven more exceeded their banks.

The record rainfall severely impacted Houston’s transportation system, resulting in damages totaling $5 million. All major highways were closed due to flooding and there was $1 million in roadway damage. (Figure 1 shows an aerial view of the flooding in Houston.)

In addition, the flooding caused more than $3 million in damage to intelligent transportation systems (ITS) and communications equipment. By June 9, the operational rates for closed circuit television cameras had been reduced by 55.6 percent; the operational rates for dynamic message signs and drum signs had been reduced by 23.8 percent.

In response to the storm and the flooding, the various partner agencies of Houston TranStar went into action. This included the Texas Department of Transportation (TxDOT), the City of Houston, Harris County and the Metropolitan Transit Authority of Harris County (METRO). The consortium of four government agencies is responsible for providing transportation and emergency management services to the greater Houston region.

Considering the magnitude of the flooding, agency staffs coped and adapted to the situation very well. The dedication of field staffs and TranStar employees was impressive. TranStar demonstrated its survivability by remaining operational while several other government agencies and private organizations, such as television stations, became non-operational. TranStar also demonstrated its ability to adapt by hosting and facilitating unexpected guests, such as the Harris County Sheriff’s Department and, ultimately, the Federal Emergency Management Agency.

By rush hour on Monday morning, June 11, all major freeways had been reopened.


After Tropical Storm Allison, TxDOT wanted to assess the areas in which the department responded well to the flood as well as the areas in which enhancements could be made. The sequence of events that occurred during June 5-10, 2001 was subjected to a detailed analysis and assessment to ascertain an accurate history and determine possible improvements in planning and operations.

Based on a list of initial questions, a series of interviews was conducted with TxDOT staff and relevant agencies. The consulting team conducted 21 interviews with 38 personnel from TxDOT, agencies associated with TranStar and others interacting with TxDOT. The consulting team also examined available data, reviewed other agency reports on the storm and events and reviewed the TxDOT flood plan.


TxDOT learned several lessons as a result of Tropical Storm Allison.

Equipment Location

The TranStar system is based on data being communicated from ITS equipment in the field to satellite buildings and, then, to TranStar. Currently, the majority of 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.

The location of equipment is important because the equipment needs to be protected from both heat and flood conditions. In addition, the communications system needs to be robust and have built-in redundancy in case a communication link is lost.

Access to Information

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.

As a result of TxDOT’s assessment, it was found that the public uses these multiple sources in an effort to collect additional information as well as to verify the information they have received from other sources.

Emergency Response

Flooding from Tropical Storm Allison hit after hours and after maintenance staff had dispersed for the weekend. In addition, 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.

Communicating Roles

There was some confusion among the agencies as to the exact role of TxDOT personnel during a flood event. TxDOT learned that it needs to communicate its role during emergencies to the other local agencies.


In response to Tropical Storm Allison, TxDOT identified several long-term goals to increase its effectiveness in responding to emergency situations. These long-term goals include:

* Designing hardware installations and communications facilities that are elevated to avoid flood damage but also built to withstand the varied climate conditions of the Houston area.

* Increasing communications capacity to support peak demand for providing information to the public and support a redundant and robust communications system that is tolerant to equipment failure.

* Ensuring that the roles of agencies are clearly defined and proper flood preparation procedures are in place, especially if flooding occurs after hours.


Currently, TxDOT is implementing several procedures and upgrading its systems to better prepare for future weather events or man-made disasters. The work in progress by TxDOT includes:

* Implementing an asynchronous transfer mode (ATM)-based communications system. This will maximize fiber availability through better management of the communications system, resulting in fewer unused fibers and more redundancy. In addition, ATM will support remote resetting of equipment and access to streaming video over the Internet.

* Designing equipment implementations to take into account the 100-year flood plane. This will minimize the risk of equipment damage during flood events.

* Upgrading the capacity of Web servers to handle the increased demand that a major emergency event creates.

* Evaluating the feasibility of wireless technologies to support redundant communications and extend communications links past the terminus of the existing fiber optic cable system.

* Working with Harris County to connect to the county fiber system and provide alternative communication routing during emergencies, based on a recent agreement between the agencies.

* Investigating the implementation of a dedicated 511 system for traveler information. With this type of system in place, the public could seek information through an automated system via telephone. The contents of a 511 call would include construction/maintenance projects, road closures, major delays, weather forecasts and road surface conditions. With this system in place, the public would have greater access to vital information pertaining to current conditions during events like Tropical Storm Allison.

* Providing a connection to the closed circuit television system in the 11 maintenance offices in the district, which will allow the maintenance offices to monitor various parts of the highway system.

* Reviewing call-out procedures for activating maintenance personnel during non-business hours.

* Investigating the statewide Highway Conditions Report system, with the possibility to migrate toward a more robust and user-friendly system.

* Expanding the coverage of the environmental sensor network on roadways. This will increase the number of roadways with environmental sensors that report weather information from around the district to TranStar. Sensor data will be accessible by TranStar operations personnel.

In addition, TxDOT recently has installed several highway advisory radio locations that can be accessed by the public for information pertaining to road conditions.


The response of TranStar partner agencies to Tropical Storm Allison shows the benefit of investing in the establishment and operation of a multi-agency advanced traffic/emergency management facility. Such a facility can provide effective and efficient management capabilities in the event of a major emergency.

The devastation of Tropical Storm Allison allowed TxDOT to identify areas that need to be enhanced. By assessing its response to the event, it can begin applying improved planning and operational management procedures.


P.E., is director of transportation operations for the Texas Department of Transportation (TxDOT), where her responsibilities include the intelligent transportation system (ITS) for TranStar; computerized transportation management systems; traffic engineering and design; traffic signal maintenance; and traffic safety. She also is a member of the leadership team for TranStar. She began working for TxDOT in 1985 in the District Design Management Section. She received a B.S. in civil engineering from Lamar University in Beaumont, TX.


P.E., is the transportation systems business manager at PBS&J in Houston, TX. He holds a bachelor’s and master’s degree in civil engineering from Virginia Tech. He has supported public agencies in the development and deployment of ITS for more than 10 years. His experience ranges from ITS planning and architecture development to detailed design and specification development. He is a member of ITE.


E.I.T., is a traffic engineer with Binkley & Barfield Inc. in Houston. She received her B.S. and M.S. in civil engineering from Texas A&M University. Her professional experience ranges from ITS design and development to transportation engineering and planning projects with an emphasis in performance measurement, systems planning and traffic operational analysis. She is an associate member of ITE.


E.I.T., is an ITS specialist far PBS&J in Houston. His areas of specialization include engineering design, planning, requirements analysis and systems development. He holds a B.S. in electrical engineering from the University of Houston and an M.B.A. from Houston Baptist University.

Copyright Institute of Transportation Engineers Aug 2003

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