As intelligent transportation systems (ITSs) evolve, the benefits include more than reductions in traffic congestion, fuel savings and fewer accidents. More efficient evacuations and emergency response are also counted among the benefits of using technology to manage traffic.
Though ITS plans are designed first for traffic management, the evolution includes the ability to plan for disaster scenarios and develop plans for evacuations based on real-time data and 21st-century tools, like evacuation software, rather than conjecture. New-age ITS tools allow officials to manage highways and roadways efficiently and mitigate ever-changing emergency situations in real time.
At the Controls
In the Dallas-Fort Worth metropolitan area, industry-standard tools for traffic management and cutting-edge software help traffic and emergency managers keep their eyes on the road. Closed-circuit TV (CCTV) cameras allow observation of the freeway, frontage roads and the arterial network to provide assessments on incidents. Dynamic message signs, located on freeways and arterials, provide a way for the traffic management centers to get information to the public about travel problems.
The region is using the National ITS Architecture as a model for developing its system. The Transportation Equity Act for the 21st Century, enacted in 1998, requires the development of systems that conform to the National ITS Architecture, which provides a common framework for planning and integrating ITSs. The standards enable transportation agencies to share and benefit from traffic management systems beyond their own, meaning traffic and emergency managers can gain a big picture view of transportation challenges and respond accordingly.
"With minimal investment, any agency can participate in a regional center-to-center communication system," said Rick Cortez, freeway management engineer for the Texas Department of Transportation (TxDOT) Dallas District. "This would allow a participating agency, at a minimum, to view the status of other agency equipment. For example, a city located in Dallas County would have the ability to view and get status from any field device TxDOT provides to the system."
According to Cortez, the TxDOT Dallas District monitors more than 100 miles of highway system within Dallas and the surrounding counties. "Incidents are detected by various means including visual verification via the CCTV cameras installed along the highway system and the use of the vehicle detection units installed along the same corridors."
TxDOT Dallas District manages a satellite traffic management center for Dallas and Tarrant counties until a permanent center can be built in the Dallas area. TxDOT's Fort Worth District manages the Western Subregion traffic center, including CCTV, lane control signals, dynamic message signs, ramp meters, mobility assistance patrols and traffic flow detectors. The traffic centers take the lead during local emergencies, directing strategy for evacuation and other traffic needs.
"In addition to the two TxDOT traffic management centers, the region has several city traffic management centers and two transit management centers throughout the region," said Sonya Jackson, principal transportation planner for the North Central Texas Council of Governments. "The traffic management centers provide an information hub around which effective system monitoring and incident detection occur."
New Model for Emergencies
The extent to which an agency or region can plan for and mitigate disaster situations will soon include some cutting-edge traffic simulation software being developed by a former University of Texas at Austin graduate student.
Yi-Chang Chiu, now an assistant professor in the University of Arizona Civil Engineering Department, has been working on the software since 1995, and it's beginning to surface as a tool for transportation and emergency management situations.
Chiu recently accepted a request from the Federal Highway Administration to use the software model to evaluate the transportation problem in Minneapolis presented by the recent bridge collapse. It will take two years to build the bridge, and in the meantime, traffic must be rerouted. Chiu's simulation software will be counted
on to show officials how and where to reroute the traffic.
Chiu is working with officials from TxDOT and several Texas cities, including El Paso and the Houston-Galveston area to test and develop the software, which will be used to simulate a central Texas evacuation and the effect of a Category 5 hurricane on Houston-Galveston, where 2 to 3 million cars would have to be evacuated inland.
It's a very complex project, said Chris Van Slyke, Houston-Galveston Area Council transportation program manager. "We haven't gotten to the point where we've put the evacuation demands into the model. We're still trying to replicate everyday traffic," he said.
Van Slyke hopes to model an evacuation by the end of this year or early next year when the kinks get worked out. "Like anything else, it's more complex than you ever imagined initially," he said.
"We'll be able to do scenario planning and make network changes to see where we can make changes to make an evacuation more efficient," Van Slyke said, "if we should contraflow [lane reversal] and if so, what facilities should be closed, how we should direct people onto the facilities, what facilities are currently not designed as an evacuation route, which ones should be and which ones we should upgrade."
Chiu said applying ITS strategies to emergency management isn't that new, but applying computer technologies and simulation techniques is. "The software we're developing is a new concept in the sense that I have not seen any state or federal emergency management agency using simulation-type techniques for developing their evacuation plans," he said.
The simulation uses traffic census data to project how drivers will react to a situation. "We represent each individual driver and their decisions responding to information," Chiu said of the software and the information it processes. "For example, if the evacuation management agency gives out different information, each driver might choose the times to leave and different routes."
Today, most evacuations are based on tabletop discussions, where officials sit down with maps and try to figure out a strategy. The software takes the guesswork out of it. "In our plan, we code geometrics characteristics into our model, and we have estimations from the population throughout the entire city," Chiu said. "So we know how many households, how many cars will leave the city at a certain time, and we also have their estimated destination and departure time."
The software works on parallel processing, which means several computers work together instead of just one. It predicts on a minute-to-minute basis which roadway will become saturated and allows emergency managers to adjust accordingly. It takes into account radio reports, what time the evacuation begins and many other factors when considering what decisions drivers will make on which route to take. The software can be matched with an air-plume dispersion model to predict how traffic will respond to an airborne hazard.
"If a nondesirable situation occurs, that gives us the idea, 'OK, this is going to be a trouble spot' and [allows us to] come up with divergent strategy to reroute traffic to a different route. Even just for planning purposes, this is one big leap compared to existing practice."
Chiu is having preliminary discussions with the Arizona DOT and emergency management offices to develop an evacuation plan for the region. The discussions involve a scenario where there's a disaster in Southern California and hundreds of thousands of people needed shelter in Phoenix.
The scenario being discussed involves both egress and ingress situations involving Phoenix. "The egress scenario will be something that happened downtown, how to evacuate people to different sister cities," Chiu explained. "The ingress will be, say something terrible happened in San Diego and L.A. Hundreds of thousands of people are trying to seek shelter in Phoenix. You start with these two scenarios and then you use the model to put all of the possible scenarios into the model, and it tells you how we can better manage the traffic in both scenarios."
The software has undergone several engineering cycles since 1995, and the next generation of it - called Multi-Resolution Assignment and Loading Traffic Activities - is nearly mature and expected to be ready for market in January 2008.
The software model might be the answer to some of our traffic woes, and it might just save lives.
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