A Study of the Impact of Nine Transportation Management Projects on Hurricane Evacuation Preparedness
In the US, hurricanes are an annual threat to the eastern and gulf coastal states. The 30 costliest and deadliest hurricanes that occurred between 1900 and 2000 resulted in $132 billion in damage and a cumulative number of deaths of almost 15,000. The average expected cost of a hurricane today is about $14 billion.
One method to reduce deaths and costs caused by hurricanes is to evacuate those areas that might be impacted. The importance of this approach has grown with recent advances in the ability of forecasters to more accurately predict the track of a hurricane, thus reducing the number of unnecessary evacuations. However, hurricane evacuations remain difficult transportation activities to manage.
By the time Hurricane Floyd reached landfall in North Carolina in 1999, roughly 3 million people evacuated from a 4-state area. This large-scale evacuation resulted in traffic jams across the regions as motorists flooded the highways. For example, travel time between Charleston and Columbia, South Carolina, normally only 2-1/2 hours, increased to almost 18 hours during the peak period.
In May 2002, FHWA funded grants to nine southeastern states (Texas, Louisiana, Mississippi, Alabama, Florida, Georgia, South Carolina, North Carolina, and Virginia) to improve transportation operations as part of their emergency management program for hurricane evacuations.
Subsequently, a lessons learned document was prepared based on the activities pursued using the federal grants.
Many coastal states have a need for near real-time traffic information to support traffic monitoring during a hurricane evacuation. Deploying traffic monitoring devices to collect this information can be expensive, particularly in rural areas where access to utilities may be limited. Ensuring that a device will work reliably during adverse circumstances, such as when a hurricane damages the power and communication systems, can be challenging. One approach to overcoming those challenges is to collaborate with the United States Geological Survey (USGS) to deploy traffic monitoring stations that share infrastructure with a USGS streamgage, used to monitor stream flow and height for flood detection. Each USGS streamgage uses battery-backed solar power and satellite communications, which makes it well-suited for deployment in remote locations and ensures it works reliably during adverse conditions. The Louisiana Department of Transportation and Development (LA DOTD) has used this approach to deploy several such combined traffic and stream monitoring stations, which LA DOTD has dubbed Information Stations.
However, several elements must be considered before the benefits of this approach can be achieved. Some of these elements are described as follows:
- Beware of operating costs in a cost-share arrangement. Operating costs of streamgages can be higher than traffic count stations. Water-level data used to estimate streamflow can change significantly over time. Therefore, USGS technicians visit streamgages about once every 6 weeks to measure the flow directly. This results in significantly higher operating costs than might be expected by state DOTs considering the operating costs of remote traffic count stations, which require less frequent service. Because USGS will typically want to share the operating costs for new streamgage installations, the high operating costs of streamgages could make an Information Station uneconomical for most state DOTs. There are some USGS streamgages that only measure water level, not streamflow, in which case lower operating costs may be possible.
- Retrofit existing streamgages with traffic count instrumentation. Because an Information Station employs unused data ports on the data logger to connect to the USGS streamgage equipment, it may be possible to retrofit existing streamgages with traffic count equipment. One approach for ensuring that an Information Station program benefits both USGS and a state DOT might be to deploy new streamgaging stations partially funded by the DOT and retrofit existing stations with DOT funds. The costs to the DOT for these new stations may be higher than other approaches for gathering traffic count information and the costs to the DOT to retrofit existing stations may be below that of other approaches. By using both low-cost add-ons to existing stations and higher cost deployment of new stations, the overall cost to the DOT may be below that of other alternatives.
- Identify funding sources other than the DOT and USGS. USGS actively collaborates with numerous partners in funding the streamgage network. In Louisiana, the Louisiana Office of Emergency Planning (LOEP) is already participating in a program to fund new streamgage stations in areas likely to flood. The LOEP also has a natural interest in helping with hurricane evacuation routes, so the combined benefits of an Information Station that could monitor flooding as well as measure evacuation traffic congestion during hurricanes was very appealing to LOEP. Local municipalities may have an interest in improving stream monitoring in flood-prone regions. By working with USGS to identify other potential funding partners, such as LOEP in this case, a DOT can reduce its portion of the costs for Information Stations.
- Consider the full range of benefits of deploying Information Stations. An Information Station does not just provide traffic count data to a state DOT, but can also provide warnings if the stream height approaches flood levels. A secondary benefit is that accurate streamflow data can help improve downstream flood stage predictions so that appropriate precautions can be taken to safeguard both the affected roads and the community. An Information Station that includes wind speed measurements can be used to identify when dangerous driving conditions exist due to excessive winds, and may also be used to identify when to close bridges during storms. Also, the USGS streamgaging network has proven itself to provide reliable data during all sorts of adverse conditions when other systems may fail. For example, damage to phone lines during a hurricane or spikes in cell phone communications can eliminate phone or cell phone communications from remote detectors. This type of failure does not affect the satellite communication network used by USGS for collecting streamgage data.
- Rely on the USGS streamgaging network. USGS has placed considerable emphasis on the reliability of the streamgaging network. The stations are capable of withstanding strong weather events. The battery/solar power supply and satellite communications used are less vulnerable to disruptions in utility services than many other approaches. Many state USGS offices have arranged partnerships with other state USGS offices to provide redundancy for the Websites that make the collected data available. These actions lead to a high level of reliability that may be difficult for individual state DOTs to match at a comparable cost.
- Consider the full range of cost savings of deploying Information Stations. Deploying a typical permanent traffic count station requires trenching to connect to local power and phone service. In many locations, these trenching costs can be a significant fraction of the overall deployment costs. Also, a data collection system must be developed and maintained, and monthly power and communication charges may be assessed. The Information Station does not require any power or phone connections and the USGS data collection system is already in place. These factors can significantly reduce the overall operating cost of an Information Station as compared to a typical traffic count station.
- Complement other DOT data collection activities using the Information Station approach. The Information Station approach to gathering near real-time traffic data is at its best in remote locations where access to power and a statewide communications network is more costly or does not exist. Even if a DOT can use an existing statewide communication network for many locations, the Information Station approach may still make sense for more remote locations.
- Recognize there may be a need to compromise in the location of the Information Stations. Information Stations must be deployed at locations where streamgage measurements are desirable for USGS. In some circumstances, this may mean that an Information Station cannot be used at a location where traffic measurements are desired because there is no nearby stream where streamgaging is desired.
- Use available USGS resources to identify existing streamgages in locations of interest. USGS online resources at http://water.usgs.gov/waterwatch/ include both maps and text descriptions of streamgage locations that can be used to identify whether streamgages already exist at locations of interest for measuring traffic counts during hurricane evacuations.
- Understand that funding partners and funding levels may change in the future. If a state DOT partners with another agency to fund an Information Station location or makes use of the USGS Cooperative Program for matching funds, then the amount of support received by this station from the initial partners may change in the future.
- Realize the frequency and amount of data collected through the USGS network is limited. Newer USGS telemetered streamgaging stations transmit data at 1-hour intervals during a 10-second time slot over a 300-baud communication channel. These criteria limit both the frequency with which data from these stations can be collected and the amount of data that can be collected. For example, these stations would not be appropriate for collecting data to support real-time decision support concerning fast changing events (e.g., incident detection) because the data collection frequency is too low. The stations would also not be appropriate for high bandwidth applications like video. However, during emergency operations, stations can access additional communications channels transmitting data more frequently. The stations could then be used for real-time decision support during emergencies, such as hurricane evacuations.
Real-time weather and traffic monitoring can provide vital information when trying to make decisions on evacuating an area before and during a hurricane. Many hurricane routes outside the more populated areas may not be equipped with traffic data collection systems because the costs to provide the infrastructure would not be feasible. If DOTs can identify innovative ways to deploy traffic count data collection and monitoring systems by seeking out other agencies that also provide hurricane data, then each agency may benefit from reduced costs for system implementation. Each agency and the public benefit from this type of collaboration since the DOT strives to make the roadways safer and the transportation system more efficient during a hurricane evacuation.