Georgia’s Express Lane systems provide significantly shorter and more reliable travel times compared with adjacent general-purpose (GP) lanes and maintain average speeds and driving cycles that are more favorable to minimizing energy use and emissions. A recent paper presented at the annual TRB meeting that assessed the optimal speeds on freeway facilities (time savings, fuel costs, safety costs, and the social cost of carbon) also concluded that 60-65 mph at smooth speeds are optimal. Customer surveys also reveal that they are highly valued by both commuters and intermittent users.
The driving cycles on these lanes (time fractions of engine loads) generally experience more cruise activity and fewer unnecessary accelerations and decelerations, given that the fleet is predominantly made up of light-duty vehicles (vehicles with more than six wheels and tractor trailers not allowed), and that there is no lane-changing behavior (restricted entrances from and exits to the GP lanes). It seems logical that maximizing the most efficient use of the facility through pricing reduces travel time, on-road energy use, and emissions. However, it has become apparent that certain navigation routing apps are currently not recommending use of managed lanes when energy optimization is enabled. This research aims to quantify costs, energy use, and emissions across the reversible toll lanes on the I-75/I-575 Northwest Corridor (NWC) and compare these results to parallel travel on the general-purpose lanes to assess the conditions under which managed lanes should be recommended.
The Georgia Tech research team proposes to expand prior analysis of the I-75/I-575 NWC Express Lanes by performing an energy use and emission assessment for these Express Lanes against the GP lanes on a per VMT basis. The tools and results from this project will support assessment and public outreach efforts related to expansion of Georgia’s Express Lanes systems.