The Georgia DOT Intelligent Transportation System, known as NaviGAtor, covers 140 freeway miles in the Atlanta metropolitan area. The NaviGAtor system includes a traffic management center (TMC), freeway management components, advanced traveler information systems, and an incident management program. TMC operators use vehicle detectors, closed circuit television (CCTV) cameras, dynamic message signs (DMS), and ramp meters to collect traffic data and manage incidents. When TMC operators identify an incident, they dispatch a Highway Emergency Response Operator (HERO) to provide motorist assistance or traffic control, and disseminate traveler information via DMS, the NaviGAtor web site (www.georgia-navigator.com), and a telephone information service (*DOT or 404-635-8000).
The benefits of the NaviGAtor incident management program were determined during a before-and-after study that analyzed twelve months of data (i.e., May 2003 to April 2004) from incident logs. The "before" conditions were estimated by analyzing incident information when a HERO could not respond, analyzing incidents that occurred outside of the NaviGAtor coverage area, and using public safety dispatch logs and personnel surveys to predict incident timelines when no NaviGAtor resources were employed. By comparing "before" conditions with "after" conditions when NaviGAtor incident management strategies were utilized, the benefits were determined in four areas: safety, mobility, energy and environment, and productivity.
The incident management program reduced annual gasoline consumption by over 5.17 million gallons and decreased diesel consumption by nearly 1.66 million gallons per year. Fuel consumption reductions were estimated based on delay savings, average speed in congestion, the percentage of cars and trucks, and the average fuel consumption of cars and trucks.
Carbon monoxide (CO) emissions fell by 2,457 tons, hydrocarbon (HC) emissions declined by 186 tons, and nitrous oxide (NOx) emissions decreased by 262 tons. Annual emissions reduction estimates were based upon vehicle-hours of incident delay and average tons per hour of emissions.