The Travel Time Index (TTI) is the relationship between the travel time in the evening peak period (3 PM – 7 PM) and travel time during non-peak periods when traffic generally flows freely. A TTI of 1.50 indicates that a 20-minute free-flow trip takes about 30 minutes or 50% longer during the peak period. The TTI is a way to understand how congestion impacts the travelers commute. The goal is to reduce congestion to a TTI of 1.3. This would mean that a 30 minute trip during non-peak hours would take no more than about 40 minutes during the peak hour period. This measure tracks the TTI along the most congested freeways in the Metro-Atlanta region.
Optimize the throughput of people and goods on network assets throughout the day. GDOT has set a peak hour TTI of 1.3 along the Interstate General Purpose lane system.
Road to Improvement
Addressing the issue of congestion within the Atlanta region is a challenge that requires time and resources. GDOT is exploring several options to improve congestion and provide choices. HOT Lanes were implemented on the I-85 North corridor, as well as Flex Shoulder Lanes on GA 400. In addition, commute options, such as teleworking, carpooling, vanpooling, and transit can help relieve congestion.